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THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 113:69È88, 1997 November
1997. The American Astronomical Society. All rights reserved. Printed in U.S.A.(
STEPS TOWARD DETERMINATION OF THE SIZE AND STRUCTURE OF THE
BROAD-LINE REGION IN ACTIVE GALACTIC NUCLEI. XI. INTENSIVE
MONITORING OF THE ULTRAVIOLET SPECTRUM OF NGC 7469
I. B. M. D. T. R. J. D. M. K.WANDERS,1,2 PETERSON,1ALLOIN,3AYRES,4CLAVEL,5CRENSHAW,6HORNE,2
G. A. J. H. M. A. H. P. T. G. A.KRISS,7KROLIK,7MALKAN,8NETZER,9OÏBRIEN,10 REICHERT,11
P. M. W. T. K. S. J.RODRIGUEZ-PASCUAL,12 WAMSTEKER,12 ALEXANDER,9,13 ANDERSON,14
E. N. G. A. N. F.-Z. S. J.BENITEZ,15 BOCHKAREV,16 BURENKOV,17 CHENG,18 COLLIER,2
A. M. D. B. R. A. V.COMASTRI,19 DIETRICH,20 DULTZIN-HACYAN,15 ESPEY,7FILIPPENKO,21
C. M. I. M. M. R. L. C. S.GASKELL,22 GEORGE,23,24 GOAD,25 HO,26 KASPI,9
W. K. T. A. G. M.KOLLATSCHNY,27 KORISTA,28 LAOR,29 MACALPINE,30
M. S. L. K. S.MIGNOLI,19 MORRIS,31 NANDRA,23,24 PENTON,4
R. W. R. L. J. M.POGGE,1PTAK,32 RODRIGUEZ-ESPINOZA,33
M. A. I. J. M.SANTOS-LLEO,34 SHAPOVALOVA,17 SHULL,35
S. A. L. S. G. M.SNEDDEN,22 SPARKE,36 STIRPE,19
W.-H. T. J. M.-H.SUN,37 TURNER,23,24 ULRICH,38
T.-G. C. W. F.WANG,18 WEI,26 WELSH,39
S.-J. AND Z.-L.XUE,18 ZOU40
Received 1997 March 24; accepted 1997 May 5
ABSTRACT
From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy
NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line
Ñuxes. From the time delays, one can estimate the size of the region dominating the production of the
UV emission lines in this source. We Ðnd the strong UV emission lines to respond to continuum varia-
tions with time delays of about for Lya, for C IV j1549, for N Vj1240, for2d.3È3d.1 2d.7 1d.9È2d.4 1d.7È1d.8
Si IV j1400, and for He II j1640. The most remarkable result, however, is the detection of appar-0d.7È1d.0
ent time delays between the di†erent UV continuum bands. With respect to the UV continuum Ñux at
1315 the Ñux at 1485 1740 and 1825 lags with time delays of and respec-Ó,Ó,Ó,Ó0d.21, 0d.35, 0d. 28,
tively. Determination of the signiÐcance of this detection is somewhat problematic since it depends on
accurate estimation of the uncertainties in the lag measurements, which are difficult to assess. We
attempt to estimate the uncertainties in the time delays through Monte Carlo simulations, and these
yield estimates of for the 1 puncertainties in the interband continuum time delays. PossibleD0d.07
explanations for the delays include the existence of a continuum-Ñux reprocessing region close to the
central source and/or a contamination of the continuum Ñux with a very broad time-delayed emission
feature such as the Balmer continuum or merged Fe II multiplets.
Subject headings: galaxies: active È galaxies : individual (NGC 7469) È galaxies : Seyfert È
ultraviolet: galaxies
1.INTRODUCTION
Numerous studies of Ñux variations in the broad emis-
sion lines of active galactic nuclei (AGNs) have established
that they respond to changes in the continuum Ñux. This
provides strong evidence for photoionization of the broad-
line region (BLR) by the central continuum source. The
time di†erence between a continuum Ñux variation and a
broad emission-line response can be attributed to light-
travel time e†ects through the BLR, which can be used to
derive the geometric and kinematic structure of the BLR
through a technique called reverberation mapping
& McKee see for a review).(Blandford 1982 ; Peterson 1993
Reverberation mapping requires high temporal sampling
of a variable AGN at high signal-to-noise ratios, over as
long a time span as possible. The International Ultraviolet
Explorer (IUE) has been well suited for this task, partly
because it can monitor AGNs without interruptions due to
weather, but primarily because the ultraviolet (UV) contin-
uum Ñux varies with larger amplitude than the optical con-
tinuum Ñux and because several important emission lines,
including Lyaj1216, C IV j1549, and He II j1640, are
emitted in the UV.
The International AGN Watch consortium et al.(Alloin
has conducted several large monitoring campaigns to1994)
obtain data suitable for reverberation-mapping analysis. In
1989, continuum and emission-line variability in the Seyfert
1 galaxy NGC 5548 was monitored for 8 months with IUE
et al. and ground-based optical telescopes(Clavel 1991)
et al. et al. et al.(Peterson 1991; Dietrich 1993; Maoz 1993 ;
et al. which produced light curves thatRomanishin 1995),
are sufficiently well resolved to yield time delays for many
strong emission lines. These data provide strong evidence
for a radially stratiÐed ionization structure for the BLR
because the low-ionization lines respond more slowly to
continuum variations than do the high-ionization lines.
Indeed, the response times for the highest ionization lines
measured, He II j1640 and N Vj1240, remained unresolved
with the 4 day sampling interval obtained with IUE.An
important result of this campaign was that the various mea-
sured continuum bands, from D1350 to D5200 vary inÓ,
phase, contrary to expectations if the continuum source has
a radial temperature gradient (as expected for a thin accre-
tion disk) or if the variations are due to disk disturbances
that propagate through the disk at the sound speed
69
70 WANDERS ET AL.
& Clavel et(Courvoisier 1991; Collin-Souffrin 1991 ; Krolik
al. A subsequent combined IUE/HST campaign in1991).
1993 with daily sampling showed that the very high ioniza-
tion lines respond to continuum variations with time delays
of about 1È3 days and placed a more stringent limit on any
UV/optical continuum phase delay et al.(Korista 1995).
Monitoring campaigns on other sources, such as NGC 3783
et al. et al. and Fairall 9(Reichert 1994; Stirpe 1994)
et al. et al.(Rodriguez-Pascual 1997; Santos-Lleo 1997),
have led to similar results.
It is generally supposed in reverberation mapping that
the light curve of an emission line L(t) is related to the
continuum light curve C(t) through
dL(t)\PdC(t[q)((q)dq, (1)
where ((q) is the geometry-dependent ““ transfer function ÏÏ
and qis a time delay & McKee One of the(Blandford 1982).
goals of AGN emission-line variability studies is to invert
this equation, solve for ((q), and thus infer, under certain
physical assumptions, the BLR geometry. Attempts to
recover the emission-line transfer functions from the exist-
ing data Welsh, & Peterson et al.(Horne, 1991; Krolik
et al. & Done have been1991 ; Wanders 1995 ; Krolik 1995)
only partially successful, primarily because of ambiguities
that arise from having a limited number of data points for
the inversion.
It must be noted that the emission-line variability is a
result of the response of the BLR to the incident ionizing
continuum radiation. This ionizing radiation is unob-
servable owing to the large optical depth of the interstellar
medium at wavelengths shorter than 912 However, theÓ.
close correlation between the observed UV continuum
variability and the responding broad emission-line variabil-
ity suggests that the observed UV continuum is a good
indicator of the unobserved ionizing continuum. Through-
out this paper, we use the observed UV continuum as if it
were the ionizing continuum, as is common practice in
reverberation studies of AGNs.
The close coupling of the variations in the various contin-
uum bands and the necessity of obtaining larger data sets
for the recovery of the transfer function have led to progres-
sively larger monitoring programs. In 1994 December, a
very intensive 10 day multiwavelength monitoring program
on NGC 4151 was carried out et al.(Crenshaw 1996; Kaspi
et al. et al. et al. This1996; Warwick 1996; Edelson 1996).
experiment led to small upper limits on any wavelength-
dependent phase di†erence in the continuum variations
(less than between 1275 and other UV bands, lessD0d.15 Ó
than between 1275 and 1.5 keV, and less than D1D0d.3 Ó
day between 1275 and 5125 but the relatively shortÓÓ),
duration of the experiment (and consequently low ampli-
tude of line variability) did not yield useful information
about the emission-line response.
1Department of Astronomy, The Ohio State University, 174 West 18th Avenue, Columbus, OH 43210.
2School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, Scotland, United Kingdom.
3Centre dÏEtudes de Saclay, Service dÏAstrophysique, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France.
4Center for Astrophysics and Space Astronomy, University of Colorado, Campus Box 389, Boulder, CO 80309.
5ISO Project, European Space Agency, Apartado 50727, 28080 Madrid, Spain.
6Computer Sciences Corporation, Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771.
7Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218.
8Department of Astronomy, University of California, Math-Science Building, Los Angeles, CA 90024.
9School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University,
Tel-Aviv 69978, Israel.
10 Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom.
11 NASA Goddard Space Flight Center, Code 631, Greenbelt, MD 20771.
12 ESA IUE Observatory, P.O. Box 50727, 28080 Madrid, Spain.
13 Max-Planck-Institut fu r extraterrestrische Physik, Postfach 1603, 85740 Garching, Germany.
14 Department of Astronomy, New Mexico State University, Box 30001, Department 4500, Las Cruces, NM 88003.
15 Universidad Nacional Autonoma de Mexico, Instituto de Astronomia, Apartado Postal 70-264, 04510 Mexico D.F., Mexico.
16 Sternberg Astronomical Institute, University of Moscow, Universitetskij Prosp. 13, Moscow 119899, Russia.
17 Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnij Arkhyz, Karachaj-Cherkess Republic, 357147, Russia.
18 Center for Astrophysics, University of Science and Technology, Hefei, Anhui, PeopleÏs Republic of China.
19 Osservatorio Astronomico di Bologna, Via Zamboni 33, I-40126, Bologna, Italy.
20 Landessternwarte, Ko nigstuhl, D-69117 Heidelberg, Germany.
21 Department of Astronomy, University of California, Berkeley, Berkeley, CA 94720.
22 Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588.
23 Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, MD 20771.
24 Universities Space Research Association.
25 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218.
26 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138.
27 Universita ts-Sternwarte Go ttingen, Geismarlandstrasse 11, D-37083 Go ttingen, Germany.
28 Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506.
29 Physics Department, Technion-Israel Institute of Technology, Haifa 32000, Israel.
30 Department of Astronomy, University of Michigan, Dennison Building, Ann Arbor, MI 48109.
31 Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria, B.C. V8X 4M6, Canada.
32 Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403.
33 Instituto de AstroÐ sica de Canarias, E-38200 La Laguna, Tenerife, Spain.
34 LAEFF, Apdo. 50727, E-28080 Madrid, Spain.
35 Joint Institute for Laboratory Astrophysics, University of Colorado, and National Institute of Standards and Technology, Campus Box 440, Boulder,
CO 80309.
36 Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706.
37 Institute of Astronomy, National Central University, Chung-Li, Taiwan 32054, Republic of China.
38 European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching, Germany.
39 McDonald Observatory and Department of Astronomy, University of Texas, RLM 15.308, Austin, TX 78712.
40 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, PeopleÏs Republic of China.
TABLE 1
LOG OF OBSERVATIONS
Start of
Image Observation Date Observation Time Exposure Time Exposure Time
(SWP Number) (UT 1996) (UT hh: mm : ss) (s) JD ([2,450,000) (days) Notesa
(1) (2) (3) (4) (5) (6) (7)
57382 ........... Jun 10 13:57:37 2700 245.10 0.031 1
57383 ........... Jun 10 23:53:46 9000 245.55 0.104 2
57384 ........... Jun 11 04:07:28 9000 245.72 0.104
57385 ........... Jun 11 08:27:28 9000 245.90 0.104
57386 ........... Jun 11 13:08:29 1740 246.06 0.020 3
57389 ........... Jun 12 01:19:23 9000 246.61 0.104
57390 ........... Jun 12 05:48:59 9000 246.79 0.104
57391 ........... Jun 12 09:57:31 9000 246.97 0.104
57395 ........... Jun 13 00:21:39 9000 247.57 0.104
57396 ........... Jun 13 04:35:14 9000 247.74 0.104
57397 ........... Jun 13 09:09:27 9000 247.93 0.104
57398 ........... Jun 13 20:44:58 9000 248.42 0.104
57399 ........... Jun 14 01:14:50 9000 248.60 0.104
57400 ........... Jun 14 05:31:40 9000 248.78 0.104
57401 ........... Jun 14 09:48:34 9000 248.96 0.104
57402 ........... Jun 14 14:54:42 4320 249.15 0.050 3
57403 ........... Jun 14 20:09:35 9000 249.39 0.104
57404 ........... Jun 15 00:23:19 9000 249.57 0.104
57405 ........... Jun 15 04:27:53 9000 249.74 0.104
57406 ........... Jun 15 08:47:31 9000 249.92 0.104
57407 ........... Jun 15 13:08:08 3420 250.07 0.040 3
57408 ........... Jun 15 20:44:59 9000 250.42 0.104
57409 ........... Jun 16 00:50:51 9000 250.59 0.104
57410 ........... Jun 16 04:57:28 9000 250.76 0.104
57411 ........... Jun 16 08:56:54 9000 250.92 0.104
57412 ........... Jun 16 22:16:32 9000 251.48 0.104
57413 ........... Jun 17 02:27:48 9000 251.65 0.104
57414 ........... Jun 17 06:17:58 9000 251.81 0.104
57415 ........... Jun 17 10:31:26 9000 251.99 0.104
57416 ........... Jun 17 21:28:08 9000 252.45 0.104
57419 ........... Jun 18 05:24:24 9000 252.78 0.104
57420 ........... Jun 18 09:35:42 9000 252.95 0.104
57421 ........... Jun 18 20:20:54 9000 253.40 0.104
57422 ........... Jun 19 00:28:12 9000 253.57 0.104
57423 ........... Jun 19 04:24:41 9000 253.74 0.104
57424 ........... Jun 19 08:31:21 9000 253.91 0.104
57425 ........... Jun 19 12:37:27 1893 254.04 0.022 3
57426 ........... Jun 19 20:09:40 9000 254.39 0.104
57427 ........... Jun 20 00:09:35 9000 254.56 0.104
57428 ........... Jun 20 04:07:37 9000 254.72 0.104
57429 ........... Jun 20 08:16:02 9000 254.90 0.104
57430 ........... Jun 20 20:39:45 9000 255.41 0.104
57431 ........... Jun 21 00:59:32 9000 255.59 0.104
57432 ........... Jun 21 05:00:41 9000 255.76 0.104
57433 ........... Jun 21 09:01:38 9000 255.93 0.104
57434 ........... Jun 21 20:40:19 9000 256.41 0.104
57435 ........... Jun 22 08:51:31 9000 256.92 0.104
57436 ........... Jun 22 20:42:24 9000 257.41 0.104 2
57439 ........... Jun 23 06:19:53 9000 257.82 0.104
57440 ........... Jun 23 10:09:22 9000 257.98 0.104
57441 ........... Jun 23 20:35:48 9000 258.41 0.104
57442 ........... Jun 24 00:39:28 9000 258.58 0.104
57443 ........... Jun 24 04:50:54 9000 258.75 0.104
57444 ........... Jun 24 09:08:43 9000 258.93 0.104
57445 ........... Jun 24 20:13:57 9000 259.40 0.104
57446 ........... Jun 25 00:42:50 9000 259.58 0.104
57447 ........... Jun 25 04:53:31 9000 259.76 0.104
57448 ........... Jun 25 09:40:52 9000 259.96 0.104
57449 ........... Jun 25 20:28:54 9000 260.41 0.104
57450 ........... Jun 26 00:54:00 9000 260.59 0.104
57451 ........... Jun 26 05:27:23 9000 260.78 0.104
57452 ........... Jun 26 09:40:47 9000 260.96 0.104
57453 ........... Jun 26 20:03:54 9000 261.39 0.104
57454 ........... Jun 26 23:16:13 9000 261.52 0.104 2
57455 ........... Jun 27 08:33:39 9000 261.91 0.104
57456 ........... Jun 27 11:29:00 7093 262.02 0.082
57457 ........... Jun 28 02:37:54 9000 262.66 0.104
57458 ........... Jun 28 07:04:56 9000 262.85 0.104
57459 ........... Jun 28 11:48:49 3600 263.01 0.042 3
57460 ........... Jun 28 19:47:32 9000 263.38 0.104
TABLE 1ÈContinued
Start of
Image Observation Date Observation Time Exposure Time Exposure Time
(SWP Number) (UT 1996) (UT hh: mm : ss) (s) JD ([2,450,000) (days) Notesa
(1) (2) (3) (4) (5) (6) (7)
57461 ........... Jun 28 23:57:04 9000 263.55 0.104
57462 ........... Jun 29 04:02:14 9000 263.72 0.104
57463 ........... Jun 29 08:09:19 9000 263.89 0.104
57464 ........... Jun 29 19:43:56 9000 264.37 0.104
57465 ........... Jun 29 23:50:18 9000 264.55 0.104
57466 ........... Jun 30 03:30:20 4320 264.70 0.050
57467 ........... Jun 30 08:39:05 9000 264.91 0.104
57468 ........... Jun 30 11:35:16 9000 265.02 0.104
57469 ........... Jun 30 19:36:01 9000 265.37 0.104
57470 ........... Jun 30 23:22:10 9000 265.53 0.104
57471 ........... Jul 1 03:04:19 9000 265.68 0.104
57472 ........... Jul 1 06:50:50 9000 265.84 0.104
57474 ........... Jul 1 19:55:01 9000 266.38 0.104
57475 ........... Jul 1 23:44:11 9000 266.54 0.104
57476 ........... Jul 2 03:25:04 9000 266.69 0.104
57477 ........... Jul 2 07:06:12 9000 266.85 0.104
57478 ........... Jul 2 10:55:19 9000 267.01 0.104
57479 ........... Jul 2 19:34:55 9000 267.37 0.104
57480 ........... Jul 2 22:31:30 9000 267.49 0.104
57481 ........... Jul 3 03:47:11 9000 267.71 0.104
57482 ........... Jul 3 06:52:14 9000 267.84 0.104
57483 ........... Jul 3 09:50:24 9000 267.96 0.104
57484 ........... Jul 3 19:41:22 9000 268.37 0.104
57485 ........... Jul 3 22:45:26 9000 268.50 0.104
57486 ........... Jul 4 03:59:04 9000 268.72 0.104
57487 ........... Jul 4 06:56:47 9000 268.84 0.104
57488 ........... Jul 4 09:55:08 9000 268.97 0.104
57489 ........... Jul 4 19:40:25 9000 269.37 0.104
57490 ........... Jul 4 22:50:04 9899 269.51 0.115
57491 ........... Jul 5 04:25:55 9899 269.74 0.115
57492 ........... Jul 5 07:50:43 9899 269.88 0.115
57493 ........... Jul 5 11:18:57 5220 270.00 0.060 4
57494 ........... Jul 5 19:45:12 9000 270.38 0.104
57495 ........... Jul 5 22:39:49 9899 270.50 0.115
57496 ........... Jul 6 04:23:08 9000 270.73 0.104
57497 ........... Jul 6 07:21:42 9000 270.86 0.104
57498 ........... Jul 6 10:18:24 9600 270.98 0.111
57499 ........... Jul 6 19:19:13 9000 271.36 0.104
57500 ........... Jul 6 22:21:01 9600 271.49 0.111
57501 ........... Jul 7 04:37:05 9000 271.74 0.104
57502 ........... Jul 7 07:35:28 9000 271.87 0.104
57504 ........... Jul 7 19:15:54 9000 272.35 0.104
57505 ........... Jul 7 22:22:19 9000 272.48 0.104
57506 ........... Jul 8 04:05:45 9000 272.72 0.104
57507 ........... Jul 8 07:06:34 9000 272.85 0.104
57508 ........... Jul 8 10:02:56 9000 272.97 0.104
57509 ........... Jul 8 19:19:25 9000 273.36 0.104
57510 ........... Jul 8 22:25:03 9000 273.49 0.104
57511 ........... Jul 9 04:13:30 9000 273.73 0.104
57512 ........... Jul 9 07:37:24 9000 273.87 0.104
57513 ........... Jul 9 11:20:37 9000 274.02 0.104
57514 ........... Jul 9 19:11:11 10200 274.36 0.118
57515 ........... Jul 9 22:29:48 9000 274.49 0.104
57516 ........... Jul 10 04:58:36 9000 274.76 0.104
57517 ........... Jul 10 08:04:27 9000 274.89 0.104
57518 ........... Jul 10 11:02:52 9000 275.01 0.104
57519 ........... Jul 10 19:08:42 9000 275.35 0.104
57520 ........... Jul 10 22:18:05 9000 275.48 0.104
57521 ........... Jul 11 04:37:22 9000 275.74 0.104
57522 ........... Jul 11 07:46:46 9000 275.88 0.104
57523 ........... Jul 11 10:43:15 9000 276.00 0.104 5
57524 ........... Jul 11 19:00:45 9000 276.34 0.104
57525 ........... Jul 11 22:19:20 9000 276.48 0.104
57526 ........... Jul 12 04:43:15 9000 276.75 0.104
57527 ........... Jul 12 07:59:13 9000 276.88 0.104 6
57528 ........... Jul 12 11:05:48 8100 277.01 0.094
57529 ........... Jul 12 19:03:54 9000 277.35 0.104
57530 ........... Jul 12 22:29:40 9000 277.49 0.104
57531 ........... Jul 13 05:27:25 9000 277.78 0.104
57532 ........... Jul 13 08:27:42 9000 277.90 0.104
57533 ........... Jul 13 11:27:37 8400 278.03 0.097
72
TABLE 1ÈContinued
Start of
Image Observation Date Observation Time Exposure Time Exposure Time
(SWP Number) (UT 1996) (UT hh: mm : ss) (s) JD ([2,450,000) (days) Notesa
(1) (2) (3) (4) (5) (6) (7)
57534 ........... Jul 13 18:56:44 9000 278.34 0.104
57535 ........... Jul 13 21:59:29 9899 278.47 0.115
57536 ........... Jul 14 04:55:41 9000 278.76 0.104
57538 ........... Jul 14 18:55:08 7364 279.33 0.085
57539 ........... Jul 14 21:52:55 9000 279.46 0.104
57540 ........... Jul 15 04:47:28 9000 279.75 0.104
57541 ........... Jul 15 08:03:41 9000 279.89 0.104
57542 ........... Jul 15 11:09:09 9000 280.02 0.104
57543 ........... Jul 15 18:57:08 9000 280.34 0.104
57544 ........... Jul 15 21:52:19 9899 280.47 0.115
57545 ........... Jul 16 04:27:09 9000 280.74 0.104
57546 ........... Jul 16 07:50:58 9000 280.88 0.104
57547 ........... Jul 16 10:58:31 9000 281.01 0.104
57548 ........... Jul 16 18:57:11 9000 281.34 0.104
57549 ........... Jul 16 21:52:12 9899 281.47 0.115
57550 ........... Jul 17 04:26:56 10800 281.75 0.125
57552 ........... Jul 17 19:11:36 9000 282.35 0.104
57553 ........... Jul 17 22:31:54 8400 282.49 0.097
57554 ........... Jul 18 05:07:08 9000 282.77 0.104
57555 ........... Jul 18 08:06:12 9000 282.89 0.104 7
57556 ........... Jul 18 11:12:46 8400 283.02 0.097
57557 ........... Jul 18 18:51:08 9000 283.34 0.104
57558 ........... Jul 18 21:52:54 9900 283.47 0.115
57559 ........... Jul 19 04:31:04 9000 283.74 0.104
57560 ........... Jul 19 07:45:56 9000 283.88 0.104
57561 ........... Jul 19 10:44:10 9000 284.00 0.104
57564 ........... Jul 19 19:08:01 9000 284.35 0.104 5
57565 ........... Jul 19 22:03:18 9000 284.47 0.104
57566 ........... Jul 20 04:36:17 9000 284.74 0.104
57567 ........... Jul 20 08:01:18 9000 284.89 0.104
57568 ........... Jul 20 11:05:19 9000 285.01 0.104
57569 ........... Jul 20 22:46:35 6600 285.49 0.076
57570 ........... Jul 21 04:52:21 9000 285.76 0.104
57571 ........... Jul 21 07:56:43 9000 285.88 0.104
57572 ........... Jul 21 10:59:18 9000 286.01 0.104
57574 ........... Jul 21 18:55:36 9000 286.34 0.104
57575 ........... Jul 21 21:51:41 9899 286.47 0.115
57576 ........... Jul 22 04:31:50 9000 286.74 0.104
57577 ........... Jul 22 07:26:26 9000 286.86 0.104
57578 ........... Jul 22 10:24:42 9000 286.99 0.104
57579 ........... Jul 22 18:46:57 9000 287.33 0.104
57580 ........... Jul 22 21:41:44 9899 287.46 0.115
57581 ........... Jul 23 04:31:22 9000 287.74 0.104
57582 ........... Jul 23 07:47:41 9000 287.88 0.104
57583 ........... Jul 23 10:43:02 9000 288.00 0.104
57584 ........... Jul 23 13:55:01 1508 288.09 0.017 3
57585 ........... Jul 23 18:55:05 9000 288.34 0.104
57586 ........... Jul 23 21:51:10 9000 288.46 0.104
57587 ........... Jul 24 04:24:03 9000 288.74 0.104
57588 ........... Jul 24 07:32:46 9000 288.87 0.104
57589 ........... Jul 24 10:33:40 9000 288.99 0.104
57590 ........... Jul 24 18:53:23 9000 289.34 0.104
57591 ........... Jul 24 21:49:18 9000 289.46 0.104
57592 ........... Jul 25 04:20:28 9000 289.73 0.104
57593 ........... Jul 25 07:39:34 9000 289.87 0.104
57594 ........... Jul 25 10:43:50 9000 290.00 0.104
57595 ........... Jul 25 18:47:15 9000 290.33 0.104
57596 ........... Jul 25 21:43:17 10200 290.46 0.118
57597 ........... Jul 26 04:12:57 9000 290.73 0.104
57598 ........... Jul 26 07:40:58 9000 290.87 0.104
57599 ........... Jul 26 10:45:00 9000 291.00 0.104
57600 ........... Jul 26 13:42:22 898 291.08 0.010 3
57601 ........... Jul 26 18:51:05 9000 291.34 0.104
57602 ........... Jul 26 21:49:15 10200 291.47 0.118
57603 ........... Jul 27 04:25:29 9000 291.74 0.104
57604 ........... Jul 27 07:55:45 9000 291.88 0.104 5
57605 ........... Jul 27 10:53:48 9000 292.01 0.104
57606 ........... Jul 27 18:39:52 9000 292.33 0.104
57607 ........... Jul 27 21:49:31 9900 292.47 0.115
57608 ........... Jul 28 04:19:07 9000 292.73 0.104
57609 ........... Jul 28 07:15:50 9000 292.85 0.104
73
74 WANDERS ET AL. Vol. 113
TABLE 1ÈContinued
Start of
Image Observation Date Observation Time Exposure Time Exposure Time
(SWP Number) (UT 1996) (UT hh: mm : ss) (s) JD ([2,450,000) (days) Notesa
(1) (2) (3) (4) (5) (6) (7)
57610 ........... Jul 28 10:23:22 9000 292.98 0.104
57611 ........... Jul 28 18:36:04 9000 293.33 0.104
57612 ........... Jul 28 21:36:51 9000 293.45 0.104 8
57613 ........... Jul 29 00:59:11 9000 293.59 0.104
57614 ........... Jul 29 04:14:46 9000 293.73 0.104
57615 ........... Jul 29 07:12:19 9000 293.85 0.104
57616 ........... Jul 29 10:10:10 9000 293.98 0.104
aNOTES.È(1) Very noisy; short exposure time. (2) Source (partly) out of aperture. (3) Source probably partly out of aperture; short
exposure time. (4) Short exposure time. (5) Large cosmic-ray blemish at He II. (6) Large cosmic-ray blemish at C IV. (7) Large cosmic-ray
blemish in continuum redward of He II. (8) Large cosmic-ray blemish around 1875 Ó.
With these results as a background, we decided to under-
take an even more intensive monitoring program to
attempt to measure both wavelength-dependent continuum
phase di†erences and emission-line responses to continuum
variations at the highest achievable time resolution for a
sustained period during the Ðnal year of IUE operations.
The original target for this investigation was the variable
Seyfert 1 galaxy Mrk 335 (see, e.g., et al.Kassebaum 1997),
but the outcome of a gyro failure in 1996 March limited
target accessibility, and we therefore selected NGC 7469,
also a known variable source Alloin, & Pelat(Salamanca,
and references therein), as an alternative target for the1995,
campaign. We will present elsewhere results based on simul-
taneous monitoring with the Rossi X-Ray T iming Explorer
et al. and ground-based optical telescopes(Nandra 1997)
et al. Spectra obtained with the Hubble Space(Collier 1997).
Telescope (HST ) during this monitoring program will be
discussed elsewhere et al. et al.(Kriss 1997; Welsh 1997).
In the observations are presented. Data analysis is°2,
described in The principal results are discussed in°3. °4,
and a summary is given in °5.
2.OBSERVATIONS
From 1996 June 10 to July 29, NGC 7469 was monitored
continuously with IUE. The time interval between the mid-
points of the last and the Ðrst spectrum was yielding48d. 84,
218 spectra, with an average sampling rate of one spectrum
per (\5.3 hr). Nearly all exposure times were 9000 s0d.22
long. All observations were made with the Short(0d.1)
Wavelength Prime (SWP) camera & Sonneborn(Harris
through the large aperture (10A]20A) of the short-1987)
wavelength spectrograph in the low-dispersion mode
(resolution D6 wavelength range 1150È1975Ó;Ó).
The log of the IUE observations is presented in Table 1.
Column (1) presents the SWP image number of the obser-
vation; column (2), the UT date at the start of the obser-
vation; column (3), the UT time at the start of the
observation; column (4), the exposure time in seconds;
column (5), the Julian Date of the middle of the observation
minus 2,450,000; and column (6), the exposure time in a
fraction of a day. Finally, column (7) presents notes to the
observations where appropriate. The 11 spectra marked
with notes (1), (2), or (3) were deemed unsuitable and were
excluded from any further analysis. The number of useful
spectra was thus reduced to N\207.
3.DATA ANALYSIS AND RESULTS
The raw images were reduced using both the standard
NEWSIPS pipeline et al. and the TOMSIPS(Nichols 1993)
reduction package These routines produced(Ayres 1993).
very similar results, although the TOMSIPS-reduced data
have somewhat smaller error bars and appear slightly
smoother to the eye. We will compare the TOMSIPS and
NEWSIPS results in the analyses, but generally they agree
well with each other.
The TOMSIPS-reduced data had a slight nonlinear
wavelength calibration error. (The low-dispersion
TOMSIPS does not compensate for long-term secular drifts
in the SWP wavelength scales, and the epoch of the original
wavelength calibration [1985] is far removed from that of
our observations of NGC 7469.) We corrected for this by
Ðtting a second-order correction polynomial to the
TOMSIPS wavelengths that aligned the peaks of the emis-
sion lines in the average TOMSIPS spectrum with the cor-
responding peaks in an HST spectrum of NGC 7469 taken
on UT 1996 June 18 et al. The wavelength(Kriss 1997).
calibration of the average NEWSIPS spectrum was found
to be in good agreement with the HST spectrum, and no
wavelength correction was applied. The spectra were then
resampled onto a 1 pixel~1 linear wavelength scale forÓ
easy comparison of the two data sets and for consistency in
further analysis.
After the linearization of the average spectrum with an
HST spectrum, small zero-point wavelength shifts between
the spectra existed in both the TOMSIPS and NEWSIPS
reduced data sets. These shifts generally were less than 1 Ó
but were as large as 2.5 in a few cases. They likely wereÓ
due to small o†sets of the target away from the center of the
large aperture as a consequence of random pointing errors
in the acquisition process. We compensated for the o†sets
by registering each spectrum to a common wavelength scale
according to the apparent sharp peak of the C IV feature.
We were able to measure its wavelength to a precision sig-
niÐcantly better than 1 This procedure resulted in aÓ.
sharpening of the average spectrum, especially for the
NEWSIPS data set, which indicated that the assumption of
constancy of the C IV peak wavelength was justiÐed.
The average wavelength of the Lyaand C IV peaks yields
a redshift z\0.0165 for NGC 7469, which is in good agree-
ment with the value given in the NASA/IPAC Extragalactic
Database (NED), z\0.0163, and is identical to the [O III]
j5007 redshift found by et al.Salamanca (1995).
3.1. Average and RMS Spectrum
For both the TOMSIPS and NEWSIPS data sets, the
average and root mean square (rms) spectra were calcu-
No. 1, 1997 BROAD-LINE REGIONS IN AGNs. XI. NGC 7469 75
lated, where the average spectrum is deÐned by
s6(j)\1
N;
i/1
N
si(j) , (2)
and the rms spectrum p(j)by
p2(j)\1
N[1;
i/1
N
[si(j)[s6(j)]2. (3)
Here is the observed spectrum at time and N\207 issi(j)ti
the total number of useful spectra.
The average and rms spectra are shown in andFigure 1,
the di†erence between the average TOMSIPS and the
average NEWSIPS spectrum is shown in TheFigure 2.
di†erence spectrum shows the general consistency of the
two methods, though there is a systematic discrepancy of up
to 13% at the red end of the spectrum, i.e., the NEWSIPS
Ñuxes are up to 13% higher than the TOMSIPS Ñuxes at
wavelengths longward of D1800 Also, the NEWSIPSÓ.
LyaÑux is systematically stronger than the TOMSIPS Lya
Ñux by D15%. These systematic di†erences do not a†ect
the results of this paper but may indicate a Ñux-calibration
Ñaw in either TOMSIPS or NEWSIPS and is potentially
important for those projects relying on accurate absolute
Ñuxes.
The average spectrum is a measure of the constant com-
ponent of the variable spectrum, and the rms spectrum is a
measure of the variable component. From the average spec-
trum we can clearly discern the broad emission lines Lya
j1216, N Vj1240, Si IV j1400, C IV j1549, He II j1640, and
CIII]j1909.
By comparing the strength of the emission lines and the
continuum in the average and rms spectra, it can be seen
FIG. 1.ÈAverage and rms IUE spectra of both the TOMSIPS (thick
line) and NEWSIPS (thin line) data for the continuous monitoring cam-
paign on NGC 7469 in 1996 JuneÈJuly. The rms spectrum is the rms
deviation from the mean spectrum. The wavelength intervals used for the
calculation of the light curves of the four continuum bands and the emis-
sion lines are also marked. All wavelengths and Ñuxes are in the observerÏs
frame.
that the line variations are much smaller than the contin-
uum variations. Some lines do not vary at all, such as C III],
which is absent from the rms spectrum.
Also apparent from the rms spectrum is the slope in the
continuum, which indicates that the continuum variations
at the blue end of the spectrum are larger than those at the
red end. This has been observed before in other AGNs (see,
e.g., Krolik, & PikeEdelson, 1990).
3.2. Continuum and Emission-L ine L ight Curves
A more detailed impression of the variability of the con-
tinuum and emission-line Ñuxes can be obtained from the
light curves.
The four continuum-Ñux light curves were determined as
the unweighted average Ñux in the (observed) wave bands
1306È1327 1473È1495 1730È1750 and 1805È1835Ó,Ó,Ó,
The wave bands are marked ““ ct1 ÏÏ to ““ ct4,ÏÏ respectively,Ó.
in Figure 1.
The emission-line light curves were determined by inte-
grating all Ñux above a pseudocontinuum level, in the
(observed) wave bands 1224È1254 for Lya, 1255È1283ÓÓ
for N V, 1224È1283 for Lya]NV, 1406È1451 for Si IV,ÓÓ
1551È1598 for C IV, 1640È1710 for He II, and 1900ÈÓÓ
1952 for C III]. The locations of these wave bands areÓ
shown in The pseudocontinuum was calculated byFigure 1.
least-squares Ðtting of a power law to all pixels in the four
continuum wave bands deÐned before. As a check of this
procedure, we also derived emission-line Ñuxes by subtrac-
ting a pseudocontinuum, which was deÐned as a straight-
line Ðt to the continuum level on each side of each emission
line. This gave consistent results with the procedure
adopted here.
Though the C IV line clearly extends beyond the tight
wavelength limits deÐned here, the rms spectrum (Fig. 1)
shows there is no signiÐcant variability in the outer parts of
the C IV emission line. In order to keep the signal-to-noise
ratio as high as possible, we integrate the line Ñux only over
the most variable part of the line. The rms spectrum was
also used to deÐne the wavelength integration limits of the
other lines. However, the width of the He II line and its low
contrast to the continuum make it difficult to deÐne its
limits in the rms spectrum; therefore, we use the average
spectrum to deÐne its limits. Because the C III] line is not
variable and thus not visible at all in the rms spectrum, we
also use the average spectrum for its limits.
The error bars of the emission-line Ñuxes are not straight-
forward to calculate because a pseudocontinuum, with
uncertain error, is subtracted before integrating over the
emission line. We have adopted a conservative approach in
this respect and estimate both the continuum and emission-
line Ñux errors by assuming there is no intrinsic variation
between two consecutive measurements. We then calculate
the rms of the distribution of the Ñux ratios andFi`1/Fi
compare this to the mean observed uncertainty as directly
derived from the spectra. We then scale the latter such that
the rms of the Ñux ratios equals the mean observed uncer-
tainty et al. This procedure pro-(Rodriguez-Pascual 1997).
duces an upper limit to the size of the error bars because in
reality, the assumption of nonvariability between consecu-
tive observations is not entirely valid.
The TOMSIPS- and NEWSIPS-derived light curves are
very similar, although the TOMSIPS data have somewhat
smaller error bars associated with the Ñuxes. The
TOMSIPS Ñuxes of the C III] line and the continuum at
76 WANDERS ET AL. Vol. 113
FIG. 2.ÈDi†erence between the average TOMSIPS and average
NEWSIPS spectrum of NGC 7469.
1825 are systematically D10% lower than the NEWSIPSÓ
Ñuxes, as are the TOMSIPS Lyaand N VÑuxes. For con-
ciseness, we tabulate only the TOMSIPS light curves in
Tables and but we show both NEWSIPS and23,
TOMSIPS light curves in Figures and respectively. All34,
Ñuxes are in the observerÏs frame.
The continuum light curves clearly show several
““ events,ÏÏ each with a duration of 10È15 days. The ampli-
tude of these variations decreases in the longer wavelength
continuum light curves, as was already evident from the
slope of the rms spectrum.
All emission-line Ñuxes are observed to possess a slow,
downward trend from the beginning to the end of the cam-
paign. The decrease in average line Ñux between the begin-
ning of the campaign and the end of the campaign is quite
large: D30% for Lya,D40% for Si IV,D25% for C IV, and
D30% for He II. These trends are possibly in response to
low-frequency continuum variability to which the present
intensive monitoring campaign is not sensitive.
Apart from the decreasing trends in the line Ñuxes, the
““ events ÏÏ in the continuum light curves can be weakly seen
in the Lya,NV,SiIV,CIV, and possibly He II light curves,
albeit with short time delays with respect to the continuum.
For example, both Lyaand C IV reach local maxima
around Julian Dates 267 and 278, approximately 2-3 days
after the continua reach their local maxima. We will quan-
tify this later by means of a cross-correlation analysis.
3.3. Variability Characteristics
We can characterize the continuum and line variability
by means of several parameters. The Ðrst two parameters
are straightforward, namely the mean Ñux and the rmsF1
Ñux deÐned in the usual manner:pF
F1\1
N;
i/1
N
Fiand pF
2\ 1
N[1;
i/1
N
(Fi[F1)2. (4)
Another useful parameter is the ratio of the maximum to
the minimum Ñux, though for some of the emissionRmax,
lines, notably He II and C III], where the random errors are
comparable to the amplitude of the intrinsic variations, this
parameter is dominated by noise and is therefore not very
meaningful.
FIG.3a
FIG. 3.ÈThe continuum (a) and emission-line (b) Ñux light curves of the NGC 7469 NEWSIPS-reduced data and the 1 perrors
No. 1, 1997 BROAD-LINE REGIONS IN AGNs. XI. NGC 7469 77
FIG.3b
A fourth parameter, is an estimate of the amplitudeFvar,
of the intrinsic variability relative to the mean Ñux, cor-
rected for the measurement errors and is deÐned asvi,
Fvar\1
F1J(pF
2[*2) , (5)
where *2is the mean square value of the measurement
uncertainties, i.e.,
*2\1
N;
i/1
N
vi
2. (6)
The four variability parameters are tabulated for each
light curve in for both the TOMSIPS (““T ÏÏ) and theTable 4
NEWSIPS (““ N ÏÏ) data. The di†erences between the
TOMSIPS and NEWSIPS results provide an estimate of
the uncertainty in these parameters. As expected, isRmax
uncertain for the He II and C III] emission lines owing to
stochastic errors in the data that are larger than the intrin-
sic variability. The parameter is also uncertain for theseFvar
lines, where *2can be larger than this is due to thepF
2;
conservative error estimates adopted here.
Parameter decreases in the continuum toward longerFvar
wavelengths, again indicating that the amplitude of the
variations decreases with increasing wavelength. Note that
for the emission lines, is relatively large owing to theFvar
trend in the data, which increases the value of For thepF
2.
emission lines, therefore, overestimates the strength ofFvar
the fast intrinsic variations.
Columns (2) and (3) of show the number of usefulTable 4
data points in the light curves. Any di†erence betweenNdata
TABLE 2
CONTINUUM FLUXES (TOMSIPS)
JD ([2,450,000) Fj(1315 Ó)Fj(1485 Ó)Fj(1740 Ó)Fj(1825 Ó)
(1) (2) (3) (4) (5)
245.72 ........... 5.39 ^0.15 4.77 ^0.20 4.84 ^0.16 3.96 ^0.13
245.90 ........... 5.31 ^0.17 4.91 ^0.21 4.56 ^0.17 4.15 ^0.14
246.61 ........... 5.31 ^0.15 4.92 ^0.20 4.57 ^0.16 4.04 ^0.13
246.79 ........... 5.25 ^0.17 5.06 ^0.21 4.88 ^0.17 4.07 ^0.14
246.97 ........... 5.42 ^0.18 4.79 ^0.23 4.45 ^0.19 4.08 ^0.15
247.57 ........... 5.33 ^0.17 5.08 ^0.21 4.10 ^0.17 3.95 ^0.14
247.74 ........... 5.30 ^0.17 5.68 ^0.21 4.27 ^0.17 4.01 ^0.14
247.93 ........... 5.12 ^0.17 4.79 ^0.21 4.39 ^0.17 3.85 ^0.14
248.42 ........... 4.97 ^0.15 4.28 ^0.20 4.09 ^0.16 3.98 ^0.13
248.60 ........... 4.86 ^0.14 4.89 ^0.19 4.48 ^0.15 4.03 ^0.12
248.96 ........... 4.76 ^0.15 4.43 ^0.21 4.18 ^0.16 3.97 ^0.13
249.39 ........... 4.99 ^0.15 4.21 ^0.20 4.24 ^0.16 3.92 ^0.13
249.57 ........... 4.71 ^0.17 4.59 ^0.21 4.29 ^0.17 3.79 ^0.14
249.74 ........... 4.89 ^0.18 4.66 ^0.24 4.06 ^0.19 4.01 ^0.15
249.92 ........... 4.68 ^0.15 4.53 ^0.21 4.23 ^0.16 3.74 ^0.13
250.42 ........... 4.50 ^0.15 4.19 ^0.20 4.14 ^0.16 3.80 ^0.13
250.59 ........... 4.19 ^0.17 4.25 ^0.22 4.09 ^0.17 3.69 ^0.14
250.76 ........... 4.33 ^0.15 4.12 ^0.20 3.88 ^0.16 3.69 ^0.13
250.92 ........... 4.37 ^0.15 4.03 ^0.20 3.88 ^0.16 3.60 ^0.13
251.48 ........... 3.90 ^0.14 . . . 3.74 ^0.15 3.64 ^0.12
251.65 ........... 3.98 ^0.18 3.73 ^0.23 3.67 ^0.19 3.44 ^0.15
251.81 ........... 3.94 ^0.15 3.69 ^0.19 3.77 ^0.16 3.56 ^0.13
251.99 ........... 3.77 ^0.18 3.67 ^0.22 3.55 ^0.19 3.29 ^0.15
252.45 ........... 3.94 ^0.13 3.62 ^0.17 3.48 ^0.13 3.57 ^0.11
252.78 ........... 3.86 ^0.14 3.53 ^0.17 3.66 ^0.15 3.38 ^0.12
252.95 ........... 3.63 ^0.14 3.28 ^0.19 3.45 ^0.15 3.45 ^0.12
253.40 ........... 3.33 ^0.13 2.91 ^0.17 3.09 ^0.13 2.82 ^0.11
253.57 ........... 3.21 ^0.14 3.20 ^0.17 3.07 ^0.15 3.03 ^0.12
253.74 ........... 3.44 ^0.14 3.37 ^0.17 3.19 ^0.15 3.19 ^0.12
253.91 ........... 3.59 ^0.13 2.96 ^0.17 3.15 ^0.13 3.12 ^0.11
254.39 ........... 3.50 ^0.13 3.06 ^0.16 3.28 ^0.13 3.09 ^0.11
254.56 ........... 3.74 ^0.13 3.44 ^0.17 3.38 ^0.13 3.42 ^0.11
254.72 ........... 4.13 ^0.15 3.48 ^0.19 3.62 ^0.16 3.19 ^0.13
254.90 ........... 3.79 ^0.13 3.63 ^0.17 3.47 ^0.13 3.23 ^0.11
255.41 ........... 4.05 ^0.17 3.74 ^0.24 3.80 ^0.20 3.42 ^0.14
255.59 ........... 4.12 ^0.18 3.64 ^0.23 3.73 ^0.19 3.37 ^0.15
255.76 ........... 4.32 ^0.15 3.95 ^0.21 3.55 ^0.16 3.44 ^0.13
255.93 ........... 3.98 ^0.17 3.65 ^0.22 3.67 ^0.17 3.35 ^0.14
256.41 ........... 4.06 ^0.15 3.76 ^0.20 3.47 ^0.16 3.35 ^0.13
256.92 ........... 3.99 ^0.14 3.54 ^0.17 3.56 ^0.15 3.65 ^0.12
257.82 ........... 4.36 ^0.14 3.94 ^0.19 3.80 ^0.15 3.48 ^0.12
257.98 ........... 4.28 ^0.15 4.07 ^0.20 3.53 ^0.16 3.51 ^0.13
258.41 ........... 4.70 ^0.15 4.02 ^0.20 3.88 ^0.16 3.75 ^0.13
258.58 ........... 4.47 ^0.15 4.18 ^0.20 3.95 ^0.16 3.74 ^0.13
258.75 ........... 4.59 ^0.15 4.41 ^0.20 3.76 ^0.16 3.62 ^0.13
258.93 ........... 4.89 ^0.14 4.31 ^0.19 3.82 ^0.15 3.74 ^0.12
259.40 ........... 4.57 ^0.14 4.17 ^0.19 4.04 ^0.15 3.69 ^0.12
259.58 ........... 4.67 ^0.14 4.43 ^0.19 3.95 ^0.15 3.70 ^0.12
259.76 ........... 4.58 ^0.18 4.45 ^0.23 3.90 ^0.19 3.81 ^0.15
259.96 ........... 4.82 ^0.17 4.58 ^0.21 4.29 ^0.17 3.75 ^0.14
260.41 ........... 4.85 ^0.17 4.18 ^0.21 4.13 ^0.17 3.76 ^0.14
260.59 ........... 4.86 ^0.17 4.31 ^0.21 4.27 ^0.17 3.74 ^0.14
260.78 ........... 5.02 ^0.19 4.22 ^0.24 4.22 ^0.20 3.82 ^0.16
260.96 ........... 4.90 ^0.18 4.68 ^0.23 4.70 ^0.19 3.62 ^0.15
261.39 ........... 4.86 ^0.14 4.51 ^0.19 4.17 ^0.15 3.89 ^0.12
261.91 ........... 4.88 ^0.14 4.49 ^0.19 4.24 ^0.15 3.88 ^0.12
262.02 ........... 5.06 ^0.17 4.53 ^0.22 4.00 ^0.17 4.03 ^0.14
262.66 ........... 5.17 ^0.15 4.69 ^0.20 4.32 ^0.16 3.94 ^0.13
262.85 ........... 5.36 ^0.14 4.80 ^0.19 4.49 ^0.16 4.10 ^0.13
263.38 ........... 5.50 ^0.17 5.00 ^0.21 4.48 ^0.17 4.17 ^0.14
263.55 ........... 5.26 ^0.17 5.37 ^0.21 4.35 ^0.17 4.15 ^0.14
263.72 ........... 5.33 ^0.18 4.78 ^0.23 4.59 ^0.19 4.12 ^0.15
263.89 ........... 5.13 ^0.15 4.63 ^0.20 4.51 ^0.16 4.08 ^0.13
264.37 ........... 5.55 ^0.14 5.40 ^0.19 4.39 ^0.15 4.17 ^0.12
264.55 ........... 5.67 ^0.19 5.01 ^0.24 4.51 ^0.20 4.12 ^0.16
264.70 ........... 5.53 ^0.15 4.97 ^0.19 4.49 ^0.16 4.24 ^0.13
264.91 ........... 5.76 ^0.15 4.97 ^0.19 4.70 ^0.16 4.42 ^0.13
265.02 ........... 4.97 ^0.23 4.92 ^0.29 4.67 ^0.24 3.80 ^0.19
265.37 ........... 5.61 ^0.18 4.91 ^0.23 4.53 ^0.19 4.11 ^0.15
265.53 ........... 5.26 ^0.17 4.65 ^0.21 4.50 ^0.17 4.08 ^0.14
265.68 ........... 5.26 ^0.19 4.85 ^0.24 4.33 ^0.20 4.02 ^0.16
265.84 ........... 5.12 ^0.19 4.74 ^0.24 4.59 ^0.20 4.06 ^0.16
TABLE 2ÈContinued
JD ([2,450,000) Fj(1315 Ó)Fj(1485 Ó)Fj(1740 Ó)Fj(1825 Ó)
(1) (2) (3) (4) (5)
266.38 ........... 4.45 ^0.14 4.47 ^0.19 3.89 ^0.15 3.49 ^0.12
266.54 ........... 4.75 ^0.15 4.61 ^0.19 4.32 ^0.16 3.76 ^0.13
266.69 ........... 4.65 ^0.15 4.36 ^0.20 4.14 ^0.16 3.83 ^0.13
266.85 ........... 4.58 ^0.19 3.99 ^0.24 4.24 ^0.20 3.65 ^0.16
267.01 ........... 4.53 ^0.15 4.44 ^0.20 3.92 ^0.16 3.81 ^0.13
267.37 ........... 4.51 ^0.14 4.10 ^0.19 4.05 ^0.15 3.73 ^0.12
267.49 ........... 4.55 ^0.15 4.41 ^0.20 4.16 ^0.16 3.84 ^0.13
267.71 ........... 4.65 ^0.17 4.13 ^0.22 4.05 ^0.17 3.87 ^0.14
267.84 ........... 4.64 ^0.18 4.15 ^0.23 3.96 ^0.19 3.75 ^0.15
267.96 ........... 4.32 ^0.17 4.34 ^0.21 3.81 ^0.17 3.79 ^0.14
268.37 ........... 4.07 ^0.17 3.76 ^0.21 3.91 ^0.17 3.56 ^0.14
268.50 ........... 4.13 ^0.15 3.72 ^0.20 3.85 ^0.16 3.41 ^0.13
268.72 ........... 4.04 ^0.14 3.72 ^0.17 3.79 ^0.15 3.52 ^0.12
268.84 ........... 3.92 ^0.17 3.92 ^0.22 3.73 ^0.17 3.42 ^0.14
268.97 ........... 3.72 ^0.17 3.90 ^0.21 3.66 ^0.17 3.25 ^0.14
269.37 ........... 3.67 ^0.14 3.04 ^0.19 3.32 ^0.15 3.03 ^0.12
269.51 ........... 3.72 ^0.14 3.50 ^0.17 3.68 ^0.15 3.42 ^0.12
269.74 ........... 3.81 ^0.13 3.52 ^0.16 3.60 ^0.13 3.31 ^0.11
269.88 ........... 3.62 ^0.17 3.87 ^0.22 3.62 ^0.17 3.12 ^0.14
270.00 ........... 3.59 ^0.23 4.32 ^0.29 3.77 ^0.24 3.28 ^0.19
270.38 ........... 3.62 ^0.13 3.24 ^0.16 3.40 ^0.13 3.33 ^0.11
270.50 ........... 3.77 ^0.15 3.30 ^0.20 3.32 ^0.16 3.26 ^0.13
270.73 ........... 3.79 ^0.14 3.44 ^0.17 3.45 ^0.15 3.26 ^0.12
270.86 ........... 3.69 ^0.14 3.44 ^0.17 3.40 ^0.15 3.31 ^0.12
270.98 ........... 3.51 ^0.18 3.35 ^0.23 3.48 ^0.19 3.35 ^0.15
271.36 ........... 3.67 ^0.15 3.29 ^0.20 3.38 ^0.16 3.28 ^0.13
271.49 ........... 3.74 ^0.13 3.46 ^0.17 3.36 ^0.13 3.27 ^0.11
271.74 ........... 3.55 ^0.14 3.19 ^0.17 3.41 ^0.15 3.26 ^0.12
271.87 ........... 3.56 ^0.17 3.30 ^0.22 3.24 ^0.17 3.16 ^0.14
272.35 ........... 3.54 ^0.13 3.03 ^0.17 3.13 ^0.13 3.00 ^0.11
272.48 ........... 3.31 ^0.17 2.76 ^0.21 3.16 ^0.17 3.12 ^0.14
272.72 ........... 3.34 ^0.15 3.04 ^0.20 3.03 ^0.16 3.04 ^0.13
272.85 ........... 3.40 ^0.14 2.95 ^0.19 3.26 ^0.15 3.04 ^0.12
272.97 ........... 3.43 ^0.14 2.94 ^0.19 3.05 ^0.15 3.21 ^0.12
273.36 ........... 3.17 ^0.13 3.08 ^0.16 3.10 ^0.13 2.93 ^0.11
273.49 ........... 3.53 ^0.15 3.15 ^0.20 2.95 ^0.16 2.91 ^0.13
273.73 ........... 3.66 ^0.14 3.12 ^0.17 3.42 ^0.15 3.11 ^0.12
273.87 ........... 3.53 ^0.14 3.22 ^0.17 3.33 ^0.15 3.21 ^0.12
274.02 ........... 3.67 ^0.18 3.12 ^0.22 3.38 ^0.19 3.10 ^0.15
274.36 ........... 3.87 ^0.11 3.51 ^0.15 3.30 ^0.13 3.27 ^0.11
274.49 ........... 3.89 ^0.17 3.59 ^0.22 3.48 ^0.17 3.22 ^0.14
274.76 ........... 3.93 ^0.14 3.67 ^0.17 3.42 ^0.15 3.35 ^0.12
274.89 ........... 3.92 ^0.14 3.51 ^0.19 3.51 ^0.15 3.34 ^0.12
275.01 ........... 4.17 ^0.18 3.26 ^0.22 3.48 ^0.19 3.37 ^0.15
275.35 ........... 4.32 ^0.14 3.98 ^0.17 3.63 ^0.15 3.48 ^0.12
275.48 ........... 4.35 ^0.14 3.68 ^0.17 3.71 ^0.15 3.48 ^0.12
275.74 ........... 4.66 ^0.14 4.35 ^0.19 3.74 ^0.15 3.69 ^0.12
275.88 ........... 4.60 ^0.15 4.27 ^0.20 3.91 ^0.16 3.70 ^0.13
276.00 ........... 4.92 ^0.20 4.65 ^0.26 4.13 ^0.21 3.58 ^0.17
276.34 ........... 4.78 ^0.15 4.10 ^0.20 4.22 ^0.16 3.92 ^0.13
276.48 ........... 4.65 ^0.14 4.39 ^0.19 4.06 ^0.15 3.68 ^0.12
276.75 ........... 4.71 ^0.17 4.42 ^0.21 4.03 ^0.17 3.61 ^0.14
276.88 ........... 5.10 ^0.15 4.05 ^0.20 4.18 ^0.16 3.87 ^0.13
277.01 ........... 4.64 ^0.17 4.10 ^0.22 4.05 ^0.17 3.61 ^0.14
277.35 ........... 4.48 ^0.15 4.20 ^0.20 3.98 ^0.16 3.71 ^0.13
277.49 ........... 4.60 ^0.18 4.32 ^0.23 4.11 ^0.19 3.77 ^0.15
277.78 ........... 4.24 ^0.14 3.96 ^0.19 3.94 ^0.15 3.69 ^0.12
277.90 ........... 4.32 ^0.18 4.05 ^0.24 3.99 ^0.19 3.80 ^0.15
278.03 ........... 4.41 ^0.19 4.07 ^0.25 3.88 ^0.20 3.47 ^0.16
278.34 ........... 4.35 ^0.15 4.04 ^0.20 3.70 ^0.16 3.67 ^0.13
278.47 ........... 4.54 ^0.15 4.13 ^0.20 3.94 ^0.16 3.54 ^0.13
278.76 ........... 4.26 ^0.15 4.11 ^0.20 3.95 ^0.16 4.02 ^0.13
279.33 ........... 4.36 ^0.17 3.91 ^0.21 3.90 ^0.17 3.54 ^0.14
279.46 ........... 4.04 ^0.14 3.95 ^0.17 3.82 ^0.15 3.53 ^0.12
279.75 ........... 3.99 ^0.15 3.89 ^0.20 4.03 ^0.16 3.90 ^0.13
279.89 ........... 4.10 ^0.14 3.75 ^0.19 3.74 ^0.15 3.80 ^0.12
280.02 ........... 3.93 ^0.15 3.84 ^0.21 4.48 ^0.16 3.52 ^0.13
280.34 ........... 4.05 ^0.14 3.94 ^0.17 4.65 ^0.15 3.48 ^0.12
280.47 ........... 3.88 ^0.14 3.71 ^0.19 3.52 ^0.15 3.46 ^0.12
280.74 ........... 3.91 ^0.15 3.78 ^0.20 3.72 ^0.16 3.60 ^0.13
280.88 ........... 3.83 ^0.15 3.82 ^0.20 3.52 ^0.16 3.23 ^0.13
281.01 ........... 3.69 ^0.17 3.49 ^0.21 3.45 ^0.17 3.37 ^0.14
BROAD-LINE REGIONS IN AGNs. XI. NGC 7469 79
TABLE 2ÈContinued
JD ([2,450,000) Fj(1315 Ó)Fj(1485 Ó)Fj(1740 Ó)Fj(1825 Ó)
(1) (2) (3) (4) (5)
281.34 ........... 3.76 ^0.14 3.71 ^0.17 3.46 ^0.15 3.41 ^0.12
281.47 ........... 4.07 ^0.13 3.67 ^0.16 3.60 ^0.13 3.52 ^0.11
281.75 ........... 4.23 ^0.13 3.89 ^0.16 3.59 ^0.13 3.63 ^0.11
282.35 ........... 4.41 ^0.15 4.13 ^0.20 3.78 ^0.16 3.95 ^0.13
282.49 ........... 4.22 ^0.15 3.91 ^0.20 3.94 ^0.16 4.31 ^0.13
282.77 ........... 4.22 ^0.14 3.68 ^0.19 3.78 ^0.15 3.76 ^0.12
282.89 ........... ... 3.84 ^0.19 4.36 ^0.15 3.87 ^0.12
283.02 ........... 4.31 ^0.17 3.69 ^0.22 3.88 ^0.17 3.64 ^0.14
283.34 ........... 4.33 ^0.14 3.82 ^0.17 3.77 ^0.15 3.63 ^0.12
283.47 ........... 4.11 ^0.15 3.51 ^0.20 3.68 ^0.16 3.56 ^0.13
283.74 ........... 4.00 ^0.15 3.67 ^0.20 3.63 ^0.16 3.41 ^0.13
283.88 ........... 4.08 ^0.14 3.76 ^0.19 3.55 ^0.15 3.55 ^0.12
284.00 ........... 4.08 ^0.15 3.68 ^0.19 3.56 ^0.16 3.31 ^0.13
284.35 ........... 3.88 ^0.15 3.80 ^0.20 3.53 ^0.16 3.46 ^0.13
284.47 ........... 3.83 ^0.14 3.53 ^0.19 3.43 ^0.15 3.48 ^0.12
284.74 ........... 3.92 ^0.15 3.68 ^0.20 3.54 ^0.16 3.27 ^0.13
284.89 ........... 4.00 ^0.14 3.48 ^0.17 3.52 ^0.15 3.36 ^0.12
285.01 ........... 3.68 ^0.18 3.36 ^0.23 3.36 ^0.19 3.51 ^0.15
285.49 ........... 3.14 ^0.20 2.98 ^0.25 3.52 ^0.21 3.14 ^0.17
285.76 ........... 3.25 ^0.13 2.91 ^0.16 2.96 ^0.13 3.04 ^0.11
285.88 ........... 3.07 ^0.15 2.83 ^0.19 3.18 ^0.16 3.05 ^0.13
286.01 ........... 3.30 ^0.17 3.33 ^0.22 3.10 ^0.17 2.95 ^0.14
286.34 ........... 3.16 ^0.15 2.74 ^0.21 3.19 ^0.17 3.04 ^0.13
286.47 ........... 3.28 ^0.13 3.03 ^0.16 3.10 ^0.13 2.95 ^0.11
286.74 ........... 2.85 ^0.17 2.61 ^0.21 3.09 ^0.17 . . .
286.86 ........... 3.02 ^0.13 2.49 ^0.17 2.94 ^0.13 2.95 ^0.12
286.99 ........... 3.24 ^0.14 2.91 ^0.17 2.92 ^0.15 2.95 ^0.12
287.33 ........... 3.01 ^0.13 3.02 ^0.16 2.94 ^0.13 3.06 ^0.11
287.46 ........... 3.06 ^0.13 2.79 ^0.15 3.09 ^0.13 2.83 ^0.11
287.74 ........... 3.03 ^0.14 2.84 ^0.19 2.83 ^0.16 2.92 ^0.13
287.88 ........... 3.04 ^0.17 2.89 ^0.21 2.97 ^0.17 3.01 ^0.14
288.00 ........... 3.30 ^0.14 2.77 ^0.19 2.85 ^0.15 2.84 ^0.12
288.34 ........... 3.05 ^0.15 2.73 ^0.19 2.84 ^0.16 2.89 ^0.13
288.46 ........... 3.30 ^0.14 3.14 ^0.19 2.89 ^0.15 2.93 ^0.12
288.74 ........... 3.05 ^0.13 2.93 ^0.17 2.91 ^0.13 2.91 ^0.11
288.87 ........... 3.36 ^0.14 3.01 ^0.17 3.11 ^0.15 2.74 ^0.12
288.99 ........... 3.14 ^0.15 2.92 ^0.20 2.99 ^0.16 2.82 ^0.13
289.34 ........... 3.46 ^0.13 3.03 ^0.16 3.14 ^0.13 3.18 ^0.11
289.46 ........... 3.70 ^0.13 3.11 ^0.16 3.38 ^0.13 3.17 ^0.11
289.73 ........... 3.60 ^0.14 3.43 ^0.19 3.51 ^0.15 3.39 ^0.12
289.87 ........... 3.88 ^0.15 3.44 ^0.20 3.48 ^0.16 3.31 ^0.13
290.00 ........... 3.93 ^0.14 3.44 ^0.19 3.43 ^0.15 3.35 ^0.12
290.33 ........... 3.51 ^0.15 3.41 ^0.20 3.27 ^0.16 2.95 ^0.13
290.46 ........... 3.56 ^0.13 3.19 ^0.16 3.02 ^0.13 2.96 ^0.11
290.73 ........... 4.36 ^0.17 4.11 ^0.21 4.09 ^0.17 3.52 ^0.14
290.87 ........... 4.32 ^0.18 4.06 ^0.23 3.71 ^0.19 3.61 ^0.15
291.00 ........... 4.25 ^0.15 4.09 ^0.20 3.86 ^0.16 3.61 ^0.13
291.34 ........... 4.35 ^0.14 3.84 ^0.19 3.89 ^0.15 3.72 ^0.12
291.47 ........... 4.39 ^0.13 3.94 ^0.17 3.84 ^0.13 3.72 ^0.11
291.74 ........... 3.99 ^0.15 3.58 ^0.20 3.88 ^0.16 3.86 ^0.13
291.88 ........... 4.10 ^0.14 3.64 ^0.19 3.78 ^0.15 3.56 ^0.12
292.01 ........... 4.25 ^0.17 4.04 ^0.21 3.98 ^0.17 3.64 ^0.14
292.33 ........... 4.37 ^0.15 4.05 ^0.20 3.82 ^0.16 3.64 ^0.13
292.47 ........... 4.45 ^0.14 3.92 ^0.19 4.12 ^0.15 3.63 ^0.12
292.73 ........... 4.42 ^0.18 3.83 ^0.23 3.83 ^0.19 3.74 ^0.15
292.85 ........... 4.43 ^0.15 4.09 ^0.19 4.04 ^0.16 3.84 ^0.13
292.98 ........... 4.37 ^0.17 4.05 ^0.22 4.01 ^0.17 3.84 ^0.14
293.33 ........... 4.71 ^0.17 4.45 ^0.22 4.33 ^0.17 3.78 ^0.14
293.45 ........... 4.52 ^0.18 4.07 ^0.24 4.14 ^0.19 3.98 ^0.15
293.59 ........... 4.46 ^0.14 4.15 ^0.19 4.02 ^0.15 3.95 ^0.12
293.73 ........... 4.69 ^0.14 4.42 ^0.19 4.00 ^0.15 3.79 ^0.12
293.85 ........... 4.66 ^0.19 4.27 ^0.24 4.24 ^0.20 3.97 ^0.16
293.98 ........... 4.74 ^0.15 4.27 ^0.19 4.10 ^0.16 3.66 ^0.13
NOTE.ÈUnits are 10~14 ergs s~1 cm~2 Ó~1.
in the TOMSIPS and NEWSIPS data is due to theNdata
fact that we have excluded from this (and forthcoming)
analysis any points whose Ñuxes are more than 5 paway
from both neighboring points. These outliers were rejected
under the assumption that they are not due to intrinsic
variability but rather are due to cosmic-ray hits or other
unidentiÐed defects in the original spectrum.
3.4. Cross-Correlation Analysis
In order to quantify the apparent time delays between the
continuum and emission-line variations and to test for pos-
sible time delays between Ñux variations in di†erent contin-
uum bands, we performed a detailed cross-correlation
analysis on both the TOMSIPS and NEWSIPS data.
We used two di†erent algorithms to compute the cross-
correlation functions (CCFs):
1. The interpolation CCF (ICCF) of & SparkeGaskell
and & Peterson in the implementation(1986) Gaskell (1987)
of & PetersonWhite (1994).
2. The discrete CCF (DCF) of & KrolikEdelson (1988)
in the implementation of & PetersonWhite (1994).
The CCF results from the TOMSIPS data are shown in
whereas both NEWSIPS and TOMSIPS resultsFigure 5,
are tabulated in The NEWSIPS and TOMSIPSTable 5.
ICCFs and DCFs are identical to within the DCF error
bars.
3.4.1. T he Continuum Bands
The most interesting cross-correlation results are the time
delays observed between the di†erent continuum bands.
Adopting the continuum at 1315 as the driver, the otherÓ
continuum wave bands lag behind with delays of 0d.19È0d.22
(1485 (1740 and (1825 TheÓ), 0d.32È0d.38 Ó), 0d.22È0d.35 Ó).
bounds given here are the di†erences in the CCF centroids
determined from the measurements based on the
TOMSIPS and NEWSIPS versions of the spectra. Taking
the average of the two reduction methods, we have lags of
and respectively. Throughout this paper,0d. 21, 0d.35, 0d. 28,
we will use the term ““ lag ÏÏ as the time delay measured from
the centroid of the CCF. We caution the reader that a ““ lagÏÏ
does not imply a simple phase shift between two light
curves.
This result was also tested by dividing the light curves
into two approximately equal subsets and again performing
cross correlations. This test yielded the same result for both
halves of the light curves, thus demonstrating that the
results obtained here are not attributable to some single
feature in the light curves.
The centroids of the CCFs are calculated at 0.8 times the
maximum correlation amplitude. If we calculate the cen-
troids at 0.5 times the maximum, the continuum delays are
slightly increased: for the TOMSIPS data, we Ðnd 0d. 23,
and respectively, for the three continuum bands,0d. 35, 0d.33,
and for the NEWSIPS data, we Ðnd and0d. 28, 0d.37, 0d. 37,
respectively. However, we will discuss only the centroids at
0.8 times the maximum correlation amplitude as this value
was also calculated in the many other AGN monitoring
campaigns (see, e.g., et al. and allows forEdelson 1996)
consistent comparison. The fact that the value of the cen-
troid is a function of its deÐnition emphasizes that the time
relations between the di†erent bands are not simple shifts.
The reason to use the CCFÏs centroid instead of its peak
position as the deÐnition of the lag between a continuum
and an emission-line light curve is because the centroid of
the CCF is directly related to the centroid of the transfer
function of & Gaskell Theequation (1) (Koratkar 1991).
centroid lag is thus a measure of the ““ luminosity-weighted ÏÏ
TABLE 3
EMISSION-LINE FLUXES (TOMSIPS)
JD ([2,450,000) LyaLya]NVNVSi IV CIV He II CIII]
(1) (2) (3) (4) (5) (6) (7) (8)
245.72 ........... 220.1 ^7.2 256.9 ^10.7 36.7 ^5.7 57.4 ^8.7 293.4 ^9.6 88.5 ^11.9 64.3 ^13.7
245.90 ........... 231.3 ^8.5 280.4 ^12.7 49.1 ^6.6 69.9 ^10.2 297.7 ^11.4 73.0 ^14.2 54.0 ^16.0
246.61 ........... 232.1 ^6.9 280.7 ^10.3 48.6 ^5.5 68.8 ^8.1 306.0 ^8.9 79.6 ^11.4 64.1 ^13.0
246.79 ........... 229.7 ^8.6 279.0 ^12.8 49.3 ^6.7 70.7 ^10.2 309.6 ^11.4 95.8 ^14.2 53.1 ^16.1
246.97 ........... 219.3 ^10.1 253.4 ^15.1 34.1 ^7.7 63.6 ^12.1 279.4 ^13.7 79.1 ^16.8 66.0 ^18.9
247.57 ........... 220.2 ^8.5 253.9 ^12.4 33.7 ^6.6 74.3 ^10.5 297.7 ^11.5 64.0 ^14.1 56.9 ^16.2
247.74 ........... 238.1 ^8.4 274.6 ^12.5 36.4 ^6.5 62.4 ^10.0 282.9 ^11.1 66.8 ^13.9 53.3 ^15.7
247.93 ........... 232.8 ^8.5 285.4 ^12.7 52.5 ^6.6 63.3 ^10.1 304.8 ^11.3 91.0 ^14.1 69.0 ^16.0
248.42 ........... 228.6 ^7.8 268.5 ^11.5 39.9 ^6.1 62.1 ^9.4 277.8 ^10.4 66.1 ^12.8 53.4 ^14.7
248.60 ........... 243.0 ^6.7 288.0 ^9.9 45.0 ^5.4 64.5 ^8.2 298.8 ^8.9 65.8 ^11.0 59.8 ^12.8
248.96 ........... 229.1 ^7.9 275.3 ^11.6 46.2 ^6.2 70.2 ^9.5 283.0 ^10.5 97.9 ^13.0 59.6 ^14.9
249.39 ........... 228.2 ^7.9 270.5 ^11.6 42.3 ^6.2 61.0 ^9.5 289.0 ^10.5 68.2 ^13.0 69.4 ^14.9
249.57 ........... 229.4 ^8.4 275.3 ^12.4 45.9 ^6.6 65.8 ^10.3 301.6 ^11.3 92.1 ^13.9 72.8 ^15.9
249.74 ........... 217.5 ^10.3 254.2 ^15.4 36.7 ^7.9 63.7 ^12.3 288.0 ^14.0 64.4 ^17.2 52.1 ^19.4
249.92 ........... 226.3 ^8.1 267.0 ^12.0 40.7 ^6.4 70.0 ^9.8 310.1 ^10.9 78.4 ^13.4 71.5 ^15.4
250.42 ........... 245.2 ^7.4 300.4 ^10.9 55.3 ^5.9 69.8 ^8.9 300.5 ^9.9 79.4 ^12.2 65.3 ^14.1
250.59 ........... 232.7 ^8.8 279.3 ^13.0 46.5 ^6.8 61.2 ^10.5 298.2 ^11.8 79.1 ^14.5 62.5 ^16.6
250.76 ........... 229.5 ^7.5 278.8 ^11.0 49.3 ^5.9 60.3 ^9.0 296.6 ^9.9 68.4 ^12.3 60.3 ^14.2
250.92 ........... 228.8 ^7.4 278.6 ^10.9 49.9 ^5.9 62.6 ^9.0 310.1 ^9.9 79.2 ^12.2 76.5 ^14.1
251.48 ........... 245.4 ^6.7 301.1 ^9.8 55.7 ^5.3 76.4 ^8.1 306.8 ^8.8 68.0 ^11.0 57.9 ^12.7
251.65 ........... 233.4 ^9.6 276.5 ^14.3 43.1 ^7.4 69.0 ^11.5 300.7 ^13.0 84.1 ^15.9 66.6 ^18.0
251.81 ........... 229.2 ^7.3 274.2 ^10.8 45.0 ^5.8 62.9 ^8.8 283.0 ^9.7 74.0 ^12.0 51.4 ^13.9
251.99 ........... 226.7 ^9.3 271.9 ^14.0 45.2 ^7.2 65.7 ^11.1 303.4 ^12.5 70.9 ^15.5 65.8 ^17.5
252.45 ........... 222.8 ^5.8 258.0 ^8.4 35.2 ^4.7 62.0 ^7.0 296.5 ^7.6 50.1 ^9.5 51.9 ^11.1
252.78 ........... 212.2 ^6.1 256.8 ^8.9 44.6 ^4.9 52.8 ^7.5 284.5 ^8.1 67.2 ^10.0 67.4 ^11.7
252.95 ........... 220.7 ^6.8 266.2 ^10.0 45.5 ^5.4 58.3 ^8.2 297.8 ^9.0 56.6 ^11.2 68.2 ^12.9
253.40 ........... ... ... 29.8 ^4.9 51.7 ^7.6 254.7 ^8.1 70.0 ^10.0 84.7 ^11.8
253.57 ........... 199.7 ^6.4 240.7 ^9.4 40.9 ^5.2 55.8 ^7.8 276.2 ^8.5 48.9 ^10.6 71.0 ^12.3
253.74 ........... 198.8 ^6.1 232.6 ^8.9 33.8 ^4.9 39.9 ^7.4 279.4 ^8.0 50.0 ^9.9 95.8 ^11.6
253.91 ........... 201.1 ^5.7 236.9 ^8.3 35.8 ^4.7 44.2 ^7.2 281.1 ^7.6 58.6 ^9.5 73.6 ^11.1
254.39 ........... 216.0 ^6.0 254.8 ^8.8 38.8 ^4.8 50.1 ^7.2 254.4 ^7.8 55.2 ^9.9 68.3 ^11.4
254.56 ........... 198.2 ^5.8 229.1 ^8.4 30.9 ^4.7 42.0 ^7.1 266.2 ^7.6 44.5 ^9.5 51.6 ^11.1
254.72 ........... 198.9 ^7.3 225.5 ^10.8 26.6 ^5.8 37.7 ^8.9 267.5 ^9.8 54.9 ^12.1 71.2 ^14.0
254.90 ........... 193.4 ^5.8 230.9 ^8.6 37.6 ^4.7 54.0 ^7.1 269.4 ^7.6 66.5 ^9.6 74.0 ^11.2
255.41 ........... 206.7 ^9.3 242.3 ^14.1 35.6 ^7.8 55.1 ^11.2 248.7 ^11.1 71.1 ^14.8 66.5 ^18.0
255.59 ........... 201.8 ^9.7 241.7 ^14.4 39.9 ^7.5 51.6 ^11.8 283.2 ^13.2 67.0 ^16.1 68.4 ^18.3
255.76 ........... 195.6 ^8.2 229.8 ^12.1 34.2 ^6.4 43.2 ^9.8 269.9 ^10.9 52.6 ^13.5 64.8 ^15.4
255.93 ........... 207.5 ^9.2 245.9 ^13.6 38.3 ^7.1 58.3 ^11.0 281.8 ^12.4 67.3 ^15.2 67.0 ^17.3
256.41 ........... 207.8 ^7.7 249.1 ^11.4 41.3 ^6.1 50.8 ^9.3 271.7 ^10.3 72.4 ^12.7 67.1 ^14.6
256.92 ........... 209.6 ^6.5 250.8 ^9.5 41.2 ^5.2 50.4 ^7.8 265.3 ^8.5 49.8 ^10.7 49.3 ^12.4
257.82 ........... 190.6 ^6.8 225.3 ^9.9 34.7 ^5.4 64.8 ^8.3 253.4 ^9.0 62.0 ^11.2 64.4 ^13.0
257.98 ........... 196.0 ^7.2 241.5 ^10.7 45.5 ^5.7 49.6 ^8.6 273.4 ^9.5 54.4 ^11.9 63.1 ^13.7
258.41 ........... 194.3 ^7.4 225.9 ^10.9 31.6 ^5.9 49.2 ^8.9 248.7 ^9.8 46.7 ^12.2 48.6 ^14.1
258.58 ........... 200.9 ^7.9 244.8 ^11.7 43.9 ^6.2 59.3 ^9.5 263.1 ^10.5 56.4 ^13.0 51.5 ^14.9
258.75 ........... 192.0 ^7.6 225.9 ^11.2 33.9 ^6.0 68.7 ^9.1 264.5 ^10.1 77.2 ^12.5 68.8 ^14.4
258.93 ........... 194.3 ^6.4 231.1 ^9.4 36.8 ^5.1 39.9 ^7.7 261.0 ^8.4 68.9 ^10.5 55.2 ^12.2
259.40 ........... 207.5 ^7.2 252.3 ^10.5 44.8 ^5.7 64.6 ^8.7 258.7 ^9.5 71.2 ^11.8 59.7 ^13.6
259.58 ........... 204.8 ^6.4 243.3 ^9.3 38.5 ^5.1 58.6 ^7.8 263.5 ^8.4 74.8 ^10.5 60.2 ^12.2
259.76 ........... 198.7 ^9.8 242.5 ^14.6 43.8 ^7.5 65.8 ^11.7 255.6 ^13.3 63.6 ^16.3 53.7 ^18.4
259.96 ........... 187.4 ^8.7 224.7 ^12.8 37.3 ^6.7 49.9 ^10.5 257.8 ^11.7 72.2 ^14.4 64.8 ^16.4
260.41 ........... 213.0 ^8.6 253.0 ^12.7 39.9 ^6.7 61.1 ^10.3 269.7 ^11.5 73.3 ^14.2 58.7 ^16.2
260.59 ........... 209.1 ^8.4 246.0 ^12.5 36.9 ^6.6 65.0 ^10.1 286.4 ^11.3 91.9 ^13.9 86.3 ^15.9
260.78 ........... 192.2 ^10.5 229.9 ^15.6 37.7 ^8.0 60.0 ^12.5 261.4 ^14.2 82.6 ^17.4 67.2 ^19.6
260.96 ........... 202.2 ^9.5 236.1 ^14.1 33.8 ^7.3 60.2 ^11.3 269.8 ^12.8 68.6 ^15.7 80.3 ^17.8
261.39 ........... 206.2 ^6.4 245.7 ^9.4 39.4 ^5.1 53.6 ^7.7 261.8 ^8.4 82.7 ^10.5 57.7 ^12.2
261.91 ........... 203.4 ^6.6 239.0 ^9.6 35.6 ^5.3 54.9 ^8.0 255.1 ^8.7 67.8 ^10.8 56.1 ^12.5
262.02 ........... 194.6 ^8.2 233.5 ^12.2 39.0 ^6.4 41.5 ^10.0 261.7 ^11.0 62.7 ^13.6 52.3 ^15.6
262.66 ........... 192.8 ^7.0 230.0 ^10.4 37.3 ^5.6 62.2 ^8.5 255.1 ^9.3 48.2 ^11.6 55.7 ^13.4
262.85 ........... 200.0 ^6.7 236.8 ^9.9 36.8 ^5.4 60.9 ^8.2 271.0 ^8.9 62.9 ^11.1 62.8 ^12.8
263.38 ........... 194.7 ^8.4 234.2 ^12.4 39.5 ^6.5 66.2 ^10.2 264.9 ^11.3 68.7 ^13.9 55.5 ^15.9
263.55 ........... 195.9 ^8.3 240.9 ^12.2 45.0 ^6.5 49.5 ^9.9 272.8 ^11.1 73.3 ^13.6 54.8 ^15.6
263.72 ........... 202.4 ^9.6 239.8 ^14.3 37.4 ^7.4 66.4 ^11.7 271.0 ^13.0 73.8 ^16.0 56.7 ^18.1
263.89 ........... 195.9 ^7.6 235.7 ^11.2 39.8 ^6.0 60.5 ^9.2 259.8 ^10.2 75.1 ^12.6 51.8 ^14.5
264.37 ........... 191.4 ^6.5 218.6 ^9.5 27.2 ^5.2 50.2 ^7.9 261.3 ^8.6 67.3 ^10.7 53.9 ^12.4
264.55 ........... 190.2 ^10.6 217.9 ^15.8 27.7 ^8.1 66.3 ^12.8 272.0 ^14.5 72.7 ^17.6 65.3 ^19.9
264.70 ........... 195.9 ^6.8 232.9 ^10.0 36.9 ^5.4 56.5 ^8.3 267.8 ^9.0 77.3 ^11.2 43.0 ^13.0
264.91 ........... 186.8 ^6.8 214.5 ^10.0 27.7 ^5.4 40.9 ^8.3 252.5 ^9.0 61.1 ^11.2 46.8 ^13.0
265.02 ........... 198.2 ^14.4 241.3 ^21.6 43.1 ^10.5 64.6 ^17.2 286.0 ^19.9 90.3 ^24.1 66.4 ^26.6
265.37 ........... 194.9 ^9.5 232.0 ^14.2 37.1 ^7.3 49.9 ^11.4 260.6 ^12.8 75.4 ^15.8 48.4 ^17.9
265.53 ........... 202.0 ^8.2 246.8 ^12.0 44.8 ^6.4 66.7 ^9.9 281.1 ^10.9 79.0 ^13.5 48.8 ^15.4
265.68 ........... 203.2 ^10.8 247.1 ^16.1 43.9 ^8.2 74.8 ^12.8 277.3 ^14.6 78.5 ^17.9 59.7 ^20.1
265.84 ........... 207.6 ^10.7 254.0 ^16.1 46.5 ^8.1 74.5 ^12.6 270.1 ^14.4 81.4 ^17.9 50.7 ^19.9
80
TABLE 3ÈContinued
JD ([2,450,000) LyaLya]NVNVSi IV CIV He II CIII]
(1) (2) (3) (4) (5) (6) (7) (8)
266.38 ........... 202.8 ^7.1 241.8 ^10.4 39.1 ^5.6 55.6 ^8.5 270.6 ^9.4 73.2 ^11.6 53.6 ^13.4
266.54 ........... 212.4 ^7.0 251.8 ^10.3 39.4 ^5.5 68.1 ^8.4 292.7 ^9.2 83.0 ^11.5 65.2 ^13.3
266.69 ........... 206.5 ^7.5 249.8 ^11.0 43.3 ^5.9 63.5 ^9.0 285.1 ^9.9 69.4 ^12.3 56.7 ^14.2
266.85 ........... 227.8 ^10.5 273.8 ^15.8 46.0 ^8.0 61.5 ^12.1 287.0 ^13.7 86.4 ^17.3 65.1 ^19.2
267.01 ........... 212.8 ^7.7 263.2 ^11.4 50.4 ^6.1 83.5 ^9.3 267.2 ^10.3 68.6 ^12.7 49.2 ^14.6
267.37 ........... 213.2 ^6.5 265.0 ^9.5 51.8 ^5.2 67.9 ^7.9 315.4 ^8.6 58.5 ^10.7 61.9 ^12.4
267.49 ........... 205.3 ^7.8 250.2 ^11.5 44.9 ^6.1 58.5 ^9.5 263.3 ^10.5 75.9 ^12.9 51.5 ^14.8
267.71 ........... 204.9 ^9.1 253.1 ^13.6 48.2 ^7.1 59.8 ^10.9 278.8 ^12.3 76.1 ^15.1 60.9 ^17.2
267.84 ........... 206.1 ^9.5 246.0 ^14.2 39.9 ^7.3 63.7 ^11.4 305.1 ^12.9 64.2 ^15.8 59.3 ^17.9
267.96 ........... 211.9 ^8.6 257.7 ^12.7 45.8 ^6.7 55.0 ^10.5 281.2 ^11.6 54.3 ^14.3 51.0 ^16.3
268.37 ........... 199.2 ^8.4 241.3 ^12.3 42.1 ^6.5 57.3 ^10.2 261.3 ^11.2 45.4 ^13.8 47.7 ^15.8
268.50 ........... 207.8 ^7.7 241.3 ^11.3 33.5 ^6.1 62.2 ^9.4 261.2 ^10.3 53.5 ^12.7 62.4 ^14.6
268.72 ........... 203.0 ^6.1 238.7 ^8.9 35.7 ^4.9 53.6 ^7.6 271.9 ^8.1 45.2 ^10.1 55.0 ^11.8
268.84 ........... 209.3 ^9.2 250.6 ^13.7 41.4 ^7.1 57.4 ^11.2 280.4 ^12.5 57.1 ^15.3 51.3 ^17.4
268.97 ........... 189.1 ^8.5 235.4 ^12.5 46.3 ^6.6 51.7 ^10.3 269.9 ^11.4 53.0 ^14.0 56.3 ^16.0
269.37 ........... ... ... 32.1 ^5.5 44.9 ^8.7 248.0 ^9.4 61.4 ^11.5 60.6 ^13.4
269.51 ........... 205.4 ^6.1 258.8 ^8.9 53.4 ^4.9 66.0 ^7.6 277.2 ^8.1 56.7 ^10.1 58.5 ^11.8
269.74 ........... 216.8 ^5.8 257.4 ^8.6 40.6 ^4.7 51.2 ^6.9 294.2 ^7.4 64.1 ^9.5 64.0 ^11.0
269.88 ........... 204.0 ^8.9 237.9 ^13.2 33.9 ^6.9 44.8 ^10.7 279.4 ^12.0 61.4 ^14.8 82.3 ^16.8
270.00 ........... 188.1 ^13.9 214.2 ^21.0 26.1 ^10.2 65.8 ^16.5 293.8 ^19.2 91.0 ^23.3 60.1 ^25.7
270.38 ........... 197.0 ^5.6 232.3 ^8.1 35.3 ^4.5 51.5 ^6.8 281.5 ^7.3 48.1 ^9.1 52.6 ^10.7
270.50 ........... 197.1 ^7.7 241.6 ^11.4 44.5 ^6.1 48.8 ^9.3 268.9 ^10.3 57.8 ^12.7 56.9 ^14.6
270.73 ........... 198.7 ^5.9 233.3 ^8.7 34.6 ^4.8 47.2 ^7.2 272.4 ^7.8 65.6 ^9.7 60.0 ^11.4
270.86 ........... 193.2 ^6.1 228.8 ^8.9 35.6 ^4.9 64.0 ^7.4 265.0 ^8.0 60.4 ^10.0 59.2 ^11.7
270.98 ........... 198.8 ^9.9 237.8 ^14.8 39.0 ^7.6 50.4 ^11.8 258.0 ^13.4 47.4 ^16.5 44.4 ^18.6
271.36 ........... 198.2 ^8.2 236.3 ^12.1 38.0 ^6.4 41.7 ^9.8 283.0 ^10.9 60.9 ^13.5 54.9 ^15.4
271.49 ........... 186.3 ^6.0 210.5 ^8.8 24.2 ^4.9 32.7 ^7.3 268.7 ^7.9 42.2 ^9.8 58.1 ^11.5
271.74 ........... 192.9 ^6.0 225.4 ^8.8 32.5 ^4.8 41.3 ^7.3 263.6 ^7.8 33.5 ^9.8 56.3 ^11.5
271.87 ........... 193.2 ^9.2 228.5 ^13.7 35.3 ^7.1 46.6 ^11.1 267.2 ^12.5 69.0 ^15.3 70.8 ^17.4
272.35 ........... 194.0 ^5.9 222.6 ^8.7 28.6 ^4.8 48.4 ^7.1 256.4 ^7.7 61.3 ^9.7 63.1 ^11.3
272.48 ........... 183.5 ^8.6 219.2 ^12.7 35.7 ^6.7 40.6 ^10.3 253.2 ^11.5 61.5 ^14.2 61.3 ^16.2
272.72 ........... 190.9 ^7.7 220.9 ^11.4 30.0 ^6.0 41.4 ^9.2 245.4 ^10.2 53.5 ^12.7 65.9 ^14.5
272.85 ........... 187.7 ^7.0 221.9 ^10.3 34.2 ^5.5 42.2 ^8.3 240.9 ^9.1 58.1 ^11.5 65.1 ^13.2
272.97 ........... 179.7 ^6.7 207.0 ^9.8 27.3 ^5.3 28.6 ^8.1 236.1 ^8.8 32.5 ^11.0 62.9 ^12.7
273.36 ........... 177.7 ^5.3 208.1 ^7.7 30.3 ^4.4 39.7 ^6.5 244.5 ^6.9 55.7 ^8.7 61.4 ^10.2
273.49 ........... 172.5 ^7.5 198.2 ^11.1 25.7 ^5.9 39.2 ^9.2 251.1 ^10.1 56.4 ^12.4 78.6 ^14.3
273.73 ........... 170.3 ^6.3 196.7 ^9.3 26.3 ^5.1 43.9 ^7.7 238.6 ^8.3 47.8 ^10.4 60.8 ^12.1
273.87 ........... 197.5 ^6.6 236.7 ^9.8 39.3 ^5.3 37.7 ^8.0 237.5 ^8.8 50.3 ^10.9 54.3 ^12.7
274.02 ........... 176.7 ^9.3 212.6 ^13.8 36.0 ^7.2 37.5 ^11.1 251.8 ^12.5 48.8 ^15.4 52.6 ^17.5
274.36 ........... 165.1 ^5.1 193.8 ^7.4 28.7 ^4.2 31.8 ^6.2 242.3 ^6.6 59.2 ^8.4 55.4 ^9.8
274.49 ........... 171.5 ^9.3 204.0 ^13.8 32.5 ^7.2 46.9 ^11.3 245.0 ^12.6 51.9 ^15.4 59.3 ^17.5
274.76 ........... 182.6 ^6.0 214.1 ^8.8 31.5 ^4.8 37.6 ^7.1 249.4 ^7.7 50.0 ^9.8 57.7 ^11.3
274.89 ........... 177.3 ^7.1 204.6 ^10.4 27.3 ^5.6 37.4 ^8.6 266.0 ^9.4 57.5 ^11.7 56.2 ^13.5
275.01 ........... 180.2 ^9.3 208.1 ^13.9 27.9 ^7.2 31.8 ^11.2 222.5 ^12.6 44.5 ^15.5 51.2 ^17.6
275.35 ........... 171.9 ^6.0 196.5 ^8.8 24.7 ^4.9 40.1 ^7.4 245.4 ^8.0 50.1 ^9.9 53.2 ^11.6
275.48 ........... 178.8 ^6.3 213.8 ^9.2 35.0 ^5.1 34.8 ^7.7 254.4 ^8.3 67.8 ^10.3 61.7 ^12.0
275.74 ........... 172.3 ^6.5 203.2 ^9.5 30.9 ^5.2 41.6 ^7.8 253.0 ^8.5 64.5 ^10.7 52.9 ^12.4
275.88 ........... 191.5 ^7.5 225.7 ^11.0 34.2 ^5.9 44.7 ^9.0 262.5 ^10.0 70.4 ^12.3 58.9 ^14.2
276.00 ........... 173.9 ^12.2 203.8 ^18.3 29.8 ^9.1 42.8 ^14.5 254.9 ^16.7 102.5 ^20.4 67.6 ^22.7
276.34 ........... 200.1 ^7.6 241.5 ^11.2 41.4 ^5.9 45.9 ^9.0 262.6 ^10.0 54.9 ^12.5 48.8 ^14.3
276.48 ........... 191.3 ^6.6 236.5 ^9.7 45.2 ^5.3 51.8 ^7.9 256.5 ^8.6 79.3 ^10.8 50.8 ^12.5
276.75 ........... 192.8 ^8.5 228.9 ^12.6 36.0 ^6.6 42.2 ^10.2 265.1 ^11.4 79.1 ^14.0 64.8 ^16.0
276.88 ........... 182.2 ^7.6 214.4 ^11.2 32.2 ^6.0 33.8 ^9.1 289.5 ^10.0 72.7 ^12.5 52.1 ^14.3
277.01 ........... 185.7 ^8.6 224.1 ^12.8 38.3 ^6.7 48.1 ^10.3 285.9 ^11.5 76.6 ^14.2 82.9 ^16.2
277.35 ........... 201.6 ^7.5 231.9 ^11.1 30.4 ^5.9 40.9 ^9.0 280.6 ^10.0 68.2 ^12.4 54.4 ^14.2
277.49 ........... 198.1 ^9.7 237.3 ^14.4 39.3 ^7.4 52.5 ^11.6 267.0 ^13.1 59.4 ^16.0 61.1 ^18.2
277.78 ........... 195.8 ^6.8 243.2 ^9.9 47.5 ^5.4 56.8 ^8.2 275.7 ^8.9 72.9 ^11.1 56.5 ^12.9
277.90 ........... 200.9 ^10.2 245.0 ^15.3 44.0 ^7.8 42.0 ^12.2 283.5 ^13.9 61.7 ^17.0 43.6 ^19.1
278.03 ........... 182.7 ^11.3 218.0 ^17.0 35.2 ^8.5 51.7 ^13.5 268.1 ^15.5 70.5 ^18.9 64.1 ^21.1
278.34 ........... 195.9 ^8.0 237.9 ^11.9 42.0 ^6.3 58.2 ^9.6 274.4 ^10.7 86.5 ^13.2 58.1 ^15.2
278.47 ........... 178.8 ^7.4 215.0 ^10.9 36.2 ^5.9 45.8 ^8.9 271.5 ^9.9 70.7 ^12.2 68.9 ^14.1
278.76 ........... 195.0 ^7.2 239.3 ^10.7 44.3 ^5.7 48.5 ^8.7 263.3 ^9.6 35.3 ^11.9 51.4 ^13.7
279.33 ........... 190.3 ^8.2 221.0 ^12.1 30.7 ^6.4 40.4 ^9.7 270.5 ^10.8 73.1 ^13.5 57.3 ^15.4
279.46 ........... 190.8 ^6.1 231.3 ^8.9 40.5 ^4.9 49.8 ^7.4 284.0 ^8.0 70.9 ^10.0 56.2 ^11.6
279.75 ........... 199.9 ^7.2 244.9 ^10.6 45.0 ^5.7 52.8 ^8.6 275.6 ^9.4 56.5 ^11.8 41.4 ^13.6
279.89 ........... 202.2 ^6.8 245.2 ^10.0 43.0 ^5.4 46.5 ^8.0 263.1 ^8.7 42.1 ^11.1 45.0 ^12.7
280.02 ........... ... 281.0 ^11.8 43.7 ^6.2 64.5 ^9.5 280.9 ^10.5 83.6 ^13.2 57.8 ^15.0
280.34 ........... 203.5 ^6.3 239.0 ^9.3 35.6 ^5.0 41.1 ^7.3 268.7 ^8.0 57.8 ^10.3 64.2 ^11.8
280.47 ........... 195.1 ^7.1 230.7 ^10.5 35.6 ^5.6 40.3 ^8.5 270.4 ^9.4 60.8 ^11.8 72.0 ^13.5
280.74 ........... 193.4 ^7.7 230.9 ^11.4 37.5 ^6.1 29.4 ^9.3 267.7 ^10.3 61.6 ^12.7 45.2 ^14.6
280.88 ........... 173.7 ^7.4 205.1 ^10.9 31.4 ^5.8 36.1 ^8.9 278.0 ^9.8 76.6 ^12.2 72.8 ^14.0
281.01 ........... 178.9 ^8.6 214.6 ^12.8 35.7 ^6.7 40.6 ^10.4 252.1 ^11.6 57.7 ^14.3 102.4 ^16.3
281.34 ........... 183.2 ^6.3 215.6 ^9.2 32.4 ^5.0 47.4 ^7.6 251.8 ^8.2 55.4 ^10.3 55.6 ^12.0
81
82 WANDERS ET AL. Vol. 113
TABLE 3ÈContinued
JD ([2,450,000) LyaLya]NVNVSi IV CIV He II CIII]
(1) (2) (3) (4) (5) (6) (7) (8)
281.47 ........... 176.2 ^5.8 207.9 ^8.5 31.7 ^4.7 37.2 ^7.0 . . . 48.6 ^9.5 60.2 ^11.1
281.75 ........... 191.3 ^5.8 225.8 ^8.5 34.4 ^4.7 46.5 ^6.9 247.1 ^7.5 45.6 ^9.5 55.8 ^11.1
282.35 ........... 184.2 ^7.5 221.6 ^11.0 37.4 ^5.9 40.9 ^9.0 249.3 ^9.9 41.9 ^12.3 28.1 ^14.2
282.49 ........... 176.7 ^7.6 214.3 ^11.2 37.6 ^6.0 30.4 ^9.2 247.9 ^10.1 40.4 ^12.5 9.5 ^14.4
282.77 ........... 185.9 ^6.9 221.8 ^10.1 35.9 ^5.4 47.8 ^8.2 257.0 ^9.0 47.6 ^11.3 50.9 ^13.0
282.89 ........... ... ... 14.7 ^5.2 20.1 ^7.9 247.5 ^8.6 39.4 ^10.7 51.4 ^12.4
283.02 ........... 188.4 ^8.3 211.4 ^12.2 23.0 ^6.5 45.0 ^9.9 263.7 ^11.1 52.3 ^13.7 53.9 ^15.6
283.34 ........... 179.2 ^6.3 206.6 ^9.2 27.4 ^5.0 43.3 ^7.6 250.5 ^8.2 57.9 ^10.3 46.9 ^12.0
283.47 ........... 179.9 ^7.8 213.4 ^11.6 33.5 ^6.1 46.0 ^9.4 257.7 ^10.4 82.9 ^12.9 50.9 ^14.8
283.74 ........... 169.4 ^7.8 195.9 ^11.5 26.5 ^6.1 50.4 ^9.4 262.2 ^10.4 56.3 ^12.9 56.8 ^14.8
283.88 ........... 190.8 ^6.4 222.7 ^9.4 31.9 ^5.2 32.2 ^7.8 258.1 ^8.4 62.5 ^10.6 57.4 ^12.3
284.00 ........... 175.0 ^6.8 200.6 ^10.1 25.6 ^5.4 42.1 ^8.2 255.1 ^9.0 96.0 ^11.2 66.2 ^13.0
284.35 ........... 188.2 ^7.7 216.6 ^11.5 28.4 ^6.1 42.6 ^9.2 259.8 ^10.2 37.7 ^12.8 47.6 ^14.6
284.47 ........... 178.4 ^6.6 220.9 ^9.6 42.5 ^5.2 55.6 ^7.9 264.8 ^8.6 51.9 ^10.8 47.5 ^12.5
284.74 ........... 163.9 ^7.5 191.5 ^11.1 27.6 ^5.9 28.1 ^9.0 258.4 ^10.0 52.3 ^12.3 55.5 ^14.2
284.89 ........... 168.5 ^6.2 194.9 ^9.1 26.4 ^5.0 38.3 ^7.5 261.8 ^8.1 76.0 ^10.2 69.7 ^11.9
285.01 ........... 174.4 ^9.6 194.7 ^14.3 20.3 ^7.4 41.5 ^11.5 238.1 ^12.9 28.4 ^15.9 38.0 ^18.0
285.49 ........... 185.3 ^11.6 231.1 ^17.4 45.8 ^8.7 41.2 ^13.8 270.0 ^15.9 58.6 ^19.4 55.0 ^21.6
285.76 ........... 166.0 ^5.7 196.5 ^8.2 30.5 ^4.6 36.5 ^6.9 257.2 ^7.4 50.9 ^9.3 56.4 ^10.9
285.88 ........... 168.8 ^7.4 202.6 ^10.9 33.8 ^5.9 41.9 ^9.1 253.1 ^9.9 53.8 ^12.2 53.2 ^14.1
286.01 ........... 155.3 ^8.8 178.6 ^13.0 23.3 ^6.8 32.1 ^10.7 240.6 ^11.9 43.6 ^14.6 62.8 ^16.6
286.34 ........... 180.4 ^8.3 218.1 ^12.4 37.7 ^6.5 44.1 ^10.0 240.4 ^11.2 55.6 ^13.8 51.0 ^15.8
286.47 ........... 164.9 ^5.3 . . . 20.4 ^4.4 22.7 ^6.5 242.5 ^7.0 39.6 ^8.7 53.7 ^10.3
286.74 ........... 185.2 ^8.7 218.8 ^12.9 33.7 ^6.7 42.5 ^10.4 238.3 ^11.7 15.5 ^14.4 . . .
286.86 ........... 174.0 ^6.0 205.4 ^8.8 31.4 ^4.9 42.9 ^7.4 233.7 ^7.9 39.8 ^9.9 58.7 ^11.6
286.99 ........... 165.3 ^6.3 191.1 ^9.2 25.8 ^5.0 19.5 ^7.6 227.9 ^8.2 38.8 ^10.3 62.0 ^12.0
287.33 ........... 170.3 ^5.3 191.2 ^7.7 20.9 ^4.3 30.7 ^6.5 237.3 ^6.9 35.6 ^8.7 53.8 ^10.2
287.46 ........... 164.9 ^5.2 186.1 ^7.6 21.2 ^4.3 20.0 ^6.3 230.1 ^6.7 33.7 ^8.5 59.3 ^10.0
287.74 ........... 162.4 ^7.3 186.2 ^10.9 23.8 ^5.8 35.9 ^8.6 222.9 ^9.4 49.6 ^12.0 57.2 ^13.7
287.88 ........... 164.8 ^8.3 189.9 ^12.3 25.1 ^6.5 44.5 ^10.0 238.0 ^11.1 37.3 ^13.8 40.5 ^15.7
288.00 ........... 148.1 ^6.8 166.6 ^10.0 18.5 ^5.4 25.9 ^8.3 211.8 ^9.0 37.8 ^11.2 67.3 ^13.0
288.34 ........... 156.3 ^7.5 178.5 ^11.0 22.2 ^5.9 30.8 ^9.0 217.5 ^9.9 47.3 ^12.3 60.6 ^14.2
288.46 ........... 152.3 ^7.1 165.7 ^10.5 13.4 ^5.7 14.2 ^8.6 217.2 ^9.5 27.3 ^11.8 47.3 ^13.6
288.74 ........... 156.8 ^6.0 182.0 ^8.8 25.2 ^4.9 42.2 ^7.3 224.1 ^7.9 35.4 ^9.9 54.9 ^11.6
288.87 ........... 150.4 ^6.3 167.9 ^9.3 17.4 ^5.1 20.0 ^7.7 212.4 ^8.4 68.3 ^10.4 64.4 ^12.1
288.99 ........... 148.6 ^7.7 174.7 ^11.2 26.0 ^6.0 23.5 ^9.3 215.5 ^10.2 37.6 ^12.6 60.7 ^14.5
289.34 ........... 150.6 ^5.4 169.8 ^7.8 19.3 ^4.4 24.3 ^6.6 215.5 ^7.0 45.6 ^8.8 41.3 ^10.3
289.46 ........... 155.4 ^5.7 174.0 ^8.3 18.6 ^4.6 30.6 ^6.9 211.8 ^7.4 38.9 ^9.3 51.9 ^10.9
289.73 ........... 150.0 ^6.9 175.3 ^10.2 25.3 ^5.5 35.3 ^8.4 215.6 ^9.2 37.0 ^11.4 35.1 ^13.2
289.87 ........... 146.0 ^7.4 165.8 ^10.9 19.8 ^5.8 24.1 ^8.8 206.4 ^9.7 49.2 ^12.2 41.4 ^13.9
290.00 ........... 148.0 ^6.5 178.0 ^9.6 30.0 ^5.2 32.6 ^7.9 212.2 ^8.6 58.9 ^10.8 54.0 ^12.5
290.33 ........... 159.0 ^8.0 188.8 ^12.1 29.8 ^6.2 32.4 ^9.1 198.8 ^10.1 54.2 ^13.2 41.4 ^14.7
290.46 ........... 144.5 ^6.0 170.9 ^8.9 26.4 ^4.8 32.7 ^7.0 197.9 ^7.6 35.9 ^9.9 35.7 ^11.3
290.73 ........... 153.7 ^8.4 170.4 ^12.3 16.7 ^6.5 39.6 ^10.1 234.3 ^11.2 62.4 ^13.8 48.8 ^15.8
290.87 ........... 164.5 ^9.9 193.5 ^14.7 29.0 ^7.6 33.0 ^12.0 237.0 ^13.5 64.7 ^16.5 47.0 ^18.6
291.00 ........... 155.7 ^7.5 181.9 ^11.1 26.3 ^5.9 37.8 ^9.0 229.2 ^10.0 61.7 ^12.4 52.2 ^14.2
291.34 ........... 174.1 ^6.6 204.2 ^9.7 30.0 ^5.3 40.1 ^8.0 236.7 ^8.7 37.5 ^10.8 44.2 ^12.6
291.47 ........... 160.1 ^5.8 179.2 ^8.5 19.1 ^4.7 41.7 ^7.0 225.4 ^7.6 53.2 ^9.5 50.5 ^11.1
291.74 ........... 176.5 ^7.9 210.3 ^11.6 33.7 ^6.2 42.8 ^9.5 252.8 ^10.5 65.2 ^13.0 33.5 ^14.9
291.88 ........... 159.8 ^6.5 190.2 ^9.5 30.5 ^5.2 47.1 ^7.9 244.8 ^8.5 93.2 ^10.6 57.2 ^12.3
292.01 ........... 150.5 ^8.6 175.1 ^12.7 24.6 ^6.7 36.6 ^10.3 251.9 ^11.5 58.5 ^14.2 47.7 ^16.2
292.33 ........... 160.8 ^7.6 189.5 ^11.3 28.7 ^6.0 40.8 ^9.1 218.9 ^10.0 66.8 ^12.6 50.8 ^14.3
292.47 ........... 172.3 ^7.0 203.3 ^10.4 31.0 ^5.6 36.0 ^8.4 228.0 ^9.2 60.3 ^11.6 54.8 ^13.3
292.73 ........... 158.0 ^9.8 181.5 ^14.6 23.5 ^7.5 37.8 ^11.7 239.3 ^13.2 71.7 ^16.2 53.5 ^18.3
292.85 ........... 168.5 ^7.0 200.3 ^10.3 31.9 ^5.6 38.7 ^8.5 245.1 ^9.3 58.0 ^11.6 53.5 ^13.4
292.98 ........... 161.0 ^9.1 192.6 ^13.5 31.6 ^7.0 45.7 ^11.1 239.0 ^12.3 48.3 ^15.1 52.4 ^17.2
293.33 ........... 163.9 ^8.8 188.8 ^13.2 24.9 ^6.8 40.6 ^10.5 239.1 ^11.8 77.8 ^14.7 59.3 ^16.6
293.45 ........... 177.4 ^10.3 201.4 ^15.5 24.0 ^7.8 42.6 ^12.2 240.5 ^13.9 58.2 ^17.3 36.7 ^19.3
293.59 ........... 173.1 ^6.8 199.8 ^10.0 26.7 ^5.4 49.2 ^8.2 235.7 ^8.9 51.7 ^11.2 44.5 ^12.9
293.73 ........... 140.4 ^6.5 160.3 ^9.5 19.8 ^5.2 44.6 ^7.8 220.1 ^8.5 65.5 ^10.6 48.1 ^12.3
293.85 ........... 151.9 ^10.8 177.4 ^16.1 25.4 ^8.2 36.9 ^12.8 229.4 ^14.6 50.1 ^17.9 38.1 ^20.1
293.98 ........... 141.9 ^6.8 160.3 ^10.0 18.4 ^5.4 55.6 ^8.3 232.5 ^9.0 63.3 ^11.2 58.5 ^13.0
NOTE.ÈUnits are 10~14 ergs cm~2 s~1.
radius of the BLR. The interpretation of peak lag of the
CCF, on the other hand, depends on the geometry of the
reprocessing region and is often biased toward the inner
regions of the reprocessing region. Furthermore, the peak
lag also depends on sampling and continuum-variability
characteristics.
The level of signiÐcance that can be ascribed to the
detected time delays between the variations in the di†erent
UV continuum bands depends on accurate determination
of the uncertainties in the time delays. Unfortunately, no
completely plausible and robust method has yet emerged to
assess the errors in cross-correlation lags derived from
limited, irregularly sampled, noisy data. Monte Carlo simu-
lations are often employed to assess these uncertainties, but
No. 1, 1997 BROAD-LINE REGIONS IN AGNs. XI. NGC 7469 83
FIG.4a
FIG. 4.ÈContinuum (a) and emission-line (b) Ñux light curves of the NGC 7469 TOMSIPS-reduced data and the 1 perrors
of course these are only as reliable as the input model that is
used. Here, we employ a simple model and Monte Carlo
simulations in an e†ort to obtain a quantitative estimate of
the accuracy of the lag determinations. The Ñuxes of both
the driving and responding light curves were reshuffled ran-
domly using Gaussian deviates based on the quoted uncer-
tainties for each data point. This was done 100 times. For
each realization, we then computed the CCF and deter-
mined the lag. We thus obtained 100 lag estimates for each
pair of light curves. The standard deviation of the distribu-
tion of lags around the mean was slightly less than for0d.07
each pair of light curves. We therefore adopt as an0d.07
estimate of the accuracy with which we can measure the lag
between the di†erent UV continuum wavebands. This is
about 3 times smaller than the average sampling interval of
about (the total integration time for each observation is0d.2
about and the remaining gaps in coverage are due to0d.1,
overheads associated with satellite control and camera
preparation). It is possible to measure lags smaller than the
sampling interval because the variations on the shortest
timescales sampled are apparently very smooth. This
assumption will be justiÐed elsewhere et al.(Welsh 1997),
based on very high time-resolution, high signal-to-noise
ratio spectra that were obtained with HST in order to
search for rapid continuum variability during this monitor-
ing campaign.
3.4.2. T he Emission L ines
As expected from inspection of the light curves and the
rms spectrum, the correlation between the continuum and
TABLE 4
VARIABILITY PARAMETERS
Ndata F1apF
aFvar Rmax
FEATURE NT N T N T N T N T
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)
Fj(1315 Ó)...... 207 206 4.19 4.20 0.68 0.65 0.15 0.15 2.01 2.02
Fj(1485 Ó)...... 205 206 4.00 3.87 0.62 0.63 0.14 0.15 2.18 2.28
Fj(1740 Ó)...... 205 207 3.85 3.77 0.51 0.47 0.13 0.12 1.84 1.73
Fj(1825 Ó)...... 200 206 3.77 3.54 0.39 0.36 0.10 0.10 1.70 1.61
Lya.............. 206 203 227.2 190.8 25.8 22.9 0.10 0.11 1.70 1.75
Lya]NV...... 206 203 267.9 226.3 34.2 30.3 0.10 0.12 1.90 1.88
NV.............. 207 207 40.7 35.0 9.9 8.6 0.14 0.17 4.58 4.15
Si IV ............. 205 207 55.4 48.6 11.9 13.1 0.17 0.19 3.69 5.86
CIV ............. 204 206 253.6 261.5 26.3 23.9 0.09 0.08 1.70 1.59
He II ............ 203 207 44.1 61.7 18.0 15.4 . . . (0.14) (248.1) (6.59)
CIII] ............ 199 206 65.9 57.6 15.2 10.9 . . . . . . (7.90) (10.81)
aUnits are 10~14 ergs cm~2 s~1 for continuum Ñuxes and 10~14 ergs cm~2 s~1 for line Ñuxes.Ó~1
84 WANDERS ET AL.
FIG.4b
emission lines is not perfect. The nonvariable C III] line
shows a nearly Ñat CCF with no signiÐcant peak. The other
emission lines all show a maximum correlation coefficient of
about 0.7. The centroid of the LyaCCF has a lag of about
(NEWSIPSÈTOMSIPS, respectively). At least two2d.3È3d.1
features can be easily identiÐed by inspection of the light
curves (the maximum in the continuum Ñux at JD B264
and the minimum at JD B288) where the Lyaline indeed
seems to respond with a delay of about Similarly, the2d.5.
lag for C IV is for Si IV the lag is and theD2d.7, D1d.7È1d.8,
He II lag is The N Vlag is but this resultD0d.7È1d.0. 1d.9È2d.4,
may be signiÐcantly contaminated by the underlying red
wing of the Lyaline, for which no attempt at correction has
been made.
The uncertainties in the lag determinations for the emis-
sion lines are larger than for the continuum, up to forD0d.8
Lya, based on the di†erence between the lags measured
from the TOMSIPS- and NEWSIPS-derived spectra.
4.DISCUSSION
The existence of time delays between the di†erent contin-
uum bands is a potentially important result. For example,
models for continuum reprocessing regions, where the
lower energy photons are reprocessed higher energy
photons originating closer to the source, predict
wavelength-dependent time delays. However, a contami-
nant broad emission feature, such as the ““ small blue bumpÏÏ
that is attributable to a blend of Balmer continuum emis-
sion and a large number of Fe II lines, with a delayed
response to the continuum variations, may also result in
wavelength-dependent time delays if the relative strength of
such an emission feature with respect to the continuum is a
function of wavelength. In the case of NGC 5548, it has
been shown that the small blue bump varies in response to
continuum variations with a response time similar to that of
Lyaand C IV et al. if the same situation holds(Maoz 1993);
FIG. 5.ÈContinuum and emission-line CCFs of the TOMSIPS-reduced NGC 7469 data. Each light curve is correlated with the continuum light curve at
1315 The ICCF is shown as a solid line and the DCF is shown as error bars.Ó.
TABLE 5
CROSS-CORRELATION RESULTS
NEWSIPS TOMSIPS
FWHM qpeak qcent FWHM qpeak qcent
FEATURE rmax (days) (days) (days) rmax (days) (days) (days)
(1) (2) (3) (4) (5) (6) (7) (8) (9)
Fj(1315 Ó) (ACF) ...... 1.00 5.10 0.00 0.00 1.00 4.94 0.00 0.00
Fj(1485 Ó).............. 0.92 5.37 0.22 0.22 0.95 5.16 0.06 0.19
Fj(1740 Ó).............. 0.91 5.21 0.08 0.38 0.93 5.10 0.08 0.32
Fj(1825 Ó).............. 0.91 5.18 0.22 0.35 0.92 4.91 0.08 0.22
Lya...................... 0.71 7.33 2.10 2.32 0.71 6.91 3.26 3.10
Lya]NV............. 0.73 7.00 2.10 2.27 0.72 6.79 3.20 2.93
NV...................... 0.68 6.09 2.10 1.90 0.66 5.34 2.20 2.39
Si IV ..................... 0.76 6.52 1.66 1.74 0.75 6.41 1.70 1.83
CIV ..................... 0.69 7.14 2.20 2.72 0.71 5.70 2.20 2.70
He II .................... 0.53 4.83 0.92 0.99 0.67 4.64 0.80 0.70
CIII] .................... 0.25 . . . . . . . . . 0.32 . . . . . . . . .
86 WANDERS ET AL. Vol. 113
in NGC 7469, the continuum delays might be plausibly
attributed to contamination by the small blue bump, which
would be expected to follow the driving continuum with a
short (D2È3 days) time delay.
In order to test how contamination by a time-delayed
component might a†ect the lags measured in this experi-
ment, we performed Monte Carlo simulations with the 1315
light curve as the driving light curve. The responding lightÓ
curve was built from two components: an undelayed copy
of the driving light curve and a delayed copy of the driving
light curve. The delay was varied in steps of and the0d.1,
strength of the delayed copy (the contaminant) was varied
from 2% to 10% with respect to the undelayed copy. The
Ñuxes of both the driving and responding light curve were
randomly reshuffled using Gaussian deviates determined
from the error estimates for each datum, and the experiment
was performed 20 times for each set of parameters. We Ðnd
that the contaminant must be at least 10% as strong as the
nondelayed responding light curve in order to have a sig-
niÐcant e†ect on the lag determinations; even in this case, if
the contaminant has a time delay as large as 2 days, the
measured lag of the contaminated light curve will be only
slightly smaller than the wavelength-dependent con-0d. 19,
tinuum lags we have found for NGC 7469. The measured
lag will not increase any further when the lag of the con-
taminant is increased, owing to the way we calculate the
position of the centroid of the CCF, which is deÐned at 0.8
times the peak value of the CCF; at larger lags, a secondary
peak of the CCF, the signature of the contaminant, appears
and is resolved. For larger lags, the contaminant is therefore
directly identiÐable in the CCF.
These contamination tests were done using a displaced
version of the driving light curve as a contaminant. In other
words, the transfer function of the contaminant was a delta
function. We also performed simulations with a transfer
function of the contaminant that was Ñat and extended over
time delays 0È2q(i.e., the transfer function for an iso-
tropically emitting thin spherical shell of radius cq). In this
model, the lag measurements are signiÐcantly smaller than
those with a delta-function transfer function, and a con-
taminant with a time delay of 2 days and a strength of 10%
of the uncontaminated light curve produces observed lags
of only 0d. 15.
Narrow spectral features that contaminate the contin-
uum Ñux bins with a strength of 10% of the continuum
variations can be ruled out from their nondetection in the
rms spectrum However, we cannot eliminate con-(Fig. 1).
taminants that are broadly distributed over much of the
width of the whole spectrum and therefore are indistin-
guishable from the actual continuum, e.g., strong Fe II emis-
sion that is clearly seen in the simultaneous HST spectrum
et al. A key test for the latter is that it implies(Kriss 1997).
that there should be no signiÐcant time delay between the
UV at 1315 and the optical continuum at around 5100ÓÓ.
This prediction will be tested in a follow-up paper present-
ing the simultaneous optical monitoring campaign (Collier
et al. 1997).
To provide a broader visual impression of the delays
present in the spectra as a function of wavelength, we have
rebinned all NEWSIPS and TOMSIPS spectra in bins of 20
per pixel and have cross-correlated each wavelength-binÓ
light curve with the continuum light curve at 1315 Ó. Figure
presents the maximum correlation coefficient and the cen-6
troid of the ICCF as a function of wavelength for both the
FIG. 6.ÈMaximum correlation coefficient and the centroid of the ICCF
as a function of wavelength for the 1996 monitoring campaign on NGC
7469. Each light curve is deÐned by a 20 wide wavelength bin and isÓ
correlated with the continuum at 1315 The thick line shows theÓ.
TOMSIPS results, the thin line the NEWSIPS results.
NEWSIPS (thin line) and TOMSIPS (thick line) data.
The maximum correlation coefficients are smaller for the
NEWSIPS data set than for the TOMSIPS data set. The
TOMSIPS extraction procedure does a(Ayres 1993)
superior job of removing Ðxed pattern noise, yielding
smoother and less noisy light curves than those we obtain
from the NEWSIPS spectra. We therefore place more con-
Ðdence in the TOMSIPS results than in the NEWSIPS
results.
The maximum correlation coefficient decreases at the
position of the emission lines in the spectrum. This is
because the lines respond with a longer lag to the driving
light curve than the underlying continuum does. The two
variable parts interfere with each other, which results in a
decrease of the correlation coefficient.
Both NEWSIPS and TOMSIPS centroid determinations
are strongly suggestive of a change in CCF centroid as a
function of wavelength outside the emission-line wave
bands. The wavelength regions of the spectrum where the
continuum variations totally dominate the emission-line
variations (see the rms spectrum in are 1300È1380Fig. 1) Ó,
1460È1540 and longward of about 1720 Even thoughÓ,Ó.
the C III] emission line contaminates the continuum spec-
trum longward of 1900 this line is known to be nonvari-Ó,
able on the timescales investigated here. The CCF is
insensitive to additive constant components, and the lag
determinations in this part of the spectrum may thus be
attributed to the continuum or to other broadly distributed
emission components.
From we can again estimate the uncertainty inFigure 6,
the continuum lag determinations, as well as obtain an esti-
mate of the signiÐcance of the result that the continuum lag
is wavelength dependent. We can assume that the lag deter-
minations between wavelength bins are independent. Thus
we can estimate the error per bin to be the root mean square
around the mean lag over Nwavelength bins. We can iden-
tify three continuum wavelength regions in 1300ÈFigure 6:
1380 1480È1520 and 1680È1940 (regions 1, 2, and 3,Ó,Ó,Ó
respectively). shows the results of the average lagTable 6
and estimated error per bin for the three continuum regions.
Column (1) shows the continuum region; column (2), the
No. 1, 1997 BROAD-LINE REGIONS IN AGNs. XI. NGC 7469 87
TABLE 6
CCF LAG ERROR ESTIMATES
Number jcenter SlagTp
Region of Bins (Ó) (days) (days)
(1) (2) (3) (4) (5)
1 ........... 5 1340 0.02 ^0.02 0.04
2 ........... 3 1500 0.13 ^0.02 0.03
3a.......... 5 1740 0.23 ^0.04 0.08
3b.......... 5 1820 0.24 ^0.04 0.10
3a]b...... 14 1810 0.34 ^0.05 0.18
number of 20 wide bins; column (3), the wavelength atÓ
which the bins are centered; column (4), the average lag
over the bins; and column (5), the root mean square p
around the average lag, i.e., the error estimate of the lag
determination per bin. The error estimates are rather upper
limits than true estimates because we assume the lag is con-
stant within each wavelength region. We Ðnd that the
weighted average of the error estimates of the four non-
overlapping wavelength regions (1, 2, 3a and 3b; see Fig. 6)
is consistent with the Monte Carlo derived estimate(0d. 08)
of the uncertainty in the continuum lag determination
(0d. 07).
Besides estimating the errors in the determination of the
CCF lag within an individual 20 wavelength bin, we canÓ
also test for the signiÐcance of the result that the CCF lags
are wavelength dependent. Our null hypothesis is that the
continuum lag is constant over the whole spectrum. The
constant can be obtained from the data by least-squares
Ðtting to the three previously deÐned continuum wave
bands of We assign a 1 perror bar of to theFigure 6. 0d.07
lag q.
The number of degrees of freedom, l, of the Ðt is the
number of wavelength bins minus the number of Ðtted
parameters, i.e., l\22 [1\21. It equals the expectation
value of the s2statistic if the model that is being Ðtted is
good. The s2statistic is our measure of goodness of Ðt and
is found to be 133 for the null hypothesis. The incomplete
gamma function Q4Q(l/2, s2/2) measures the probability
Qthat the s2is larger than its value by chance. [For a
discussion of Q(l/2, s2/2), see et al. A smallPress 1992.]
value of Qthus signiÐes a very poor Ðt, whereas a([10~8)
large value of QsigniÐes a reasonable to good Ðt.(Z10~3)
For s2\133 and l\21, Q>10~8 and the null hypothesis
can be ruled out as a good representation of the data with
great conÐdence.
5.SUMMARY
A 7 week continuous monitoring campaign on the Seyfert
1 nucleus NGC 7469 was conducted with the IUE satellite
during 1996 JuneÈJuly. SigniÐcant continuum variability
was detected, and the emission lines also varied but with
much smaller amplitude. The results can be summarized as
follows.
1. The continuum light curves exhibit a wavelength-
dependent lag relative to the continuum variations at 1315
at 1485 at 1740 and at 1825Ó:qB0d.19 Ó,0d.32 Ó,0d.22 Ó
for the TOMSIPS-reduced data, and and0d.22, 0d.38, 0d.35,
respectively, for the NEWSIPS-reduced data. The average
lags are and respectively. The presence of0d.21, 0d. 35, 0d.28,
wavelength-dependent continuum lags is further demon-
strated by a more detailed analysis over all wavelengths in
the spectra We estimate through Monte Carlo(Fig. 6).
simulations that the uncertainty in these determinations is
about although we emphasize that there is no general0d. 07,
agreement about how such uncertainties should be deter-
mined. Furthermore, on the basis of the UV data alone, we
are unable to determine deÐnitively whether the lags are
due (1) to actual wavelength dependence of the continuum
variations, as might be expected if the UV continuum at
longer wavelengths is reprocessed emission from shorter
wavelength photons, or (2) to contamination of the mea-
sured continuum by a very broad, delayed emission feature,
such as the ““ small blue bump,ÏÏ which becomes progres-
sively stronger toward the red part of the spectrum. Con-
current optical observations et al. combined(Collier 1997),
with these data, will provide a more deÐnitive test of the
reality of this phenomenon, and if it is indeed real, much
stronger constraints on its possible origin.
2. The amplitude of the continuum variations at the
longer wavelengths is smaller than at the shorter wave-
lengths, which thus conÐrms the results of previous studies.
3. The Lya,SiIV,andCIV emission lines lag behind the
continuum variations by about whereas the He II2d.3È3d.1,
line has a lag of about and the C III] line does not0d.7È1d.0,
respond to the rapid continuum variations at all. The vari-
able part of the broad lines arises in gas at a typical distance
of about 3 lt-days from the continuum source.
4. All emission lines show a decreasing trend in their
total Ñux from the beginning to the end of the monitoring
campaign. This trend is also seen in the continuum Ñuxes
and may be attributed to much longer continuum-
variability timescales.
We gratefully acknowledge support for this work by
NASA through grants NAG 5-2477 and NAG 5-3497.
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