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The XMM-Newton survey of the Small Magellanic Cloud

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F. Haberl
F. Haberl
F. Haberl
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R. Sturm at Max Planck Institute for Extraterrestrial Physics
R. Sturm
J. Ballet
J. Ballet
J. Ballet
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Dominik J. Bomans at Ruhr-Universität Bochum
Dominik J. Bomans
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Abstract

Although numerous archival XMM-Newton observations existed towards the Small Magellanic Cloud (SMC) before 2009, only a fraction of the whole galaxy was covered. Between May 2009 and March 2010 we carried out an XMM-Newton survey of the SMC, in order to obtain a complete overage of both its bar and wing. Thirty-three observations of 30 different fields with a total exposure of about ne Ms filled the missing parts. We systematically processed all available SMC data from the European Photon Imaging Camera. After rejecting observations with very high background we included 53 archival and the 33 survey observations. We produced images in five different energy bands. We applied astrometric boresight corrections using secure identifications of X-ray sources and combine all the images to produce a mosaic, which covers the main body of the SMC. We present an overview of the XMM-Newton observations, describe their analysis and summarise first results which will be presented in follow-up papers in detail. Here, we mainly focus on extended X-ray sources like supernova remnants (SNRs) and clusters of galaxies which are seen in our X-ray images. The XMM-Newton survey represents the deepest complete survey of the SMC in the 0.15-12.0 keV X-ray band. We propose three new SNRs with low surface brightness of a few 10^-14 erg s^-1 cm^-2 arcmin^-2 and large extent. Also several known remnants appear larger than previously measured from X-rays or other wavelengths extending the size distribution of SMC SNRs to larger values.
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Frank Haberl
Max-Planck-Institut für
extraterrestrische Physik
Garching, Germany
The XMM-Newton survey of the Small Magellanic Cloud
•History of X-ray observations of the SMC
•Archival XMM-Newton observations
•The XMM-Newton survey
- Source catalogue
- Population studies
SSS, HMXBs, SNRs
An XMM-Newton large project in collaboration with
J. Ballet, D. Bomans, D.A.H. Buckley, M.J. Coe, R. Corbet, M. Ehle, M.D. Filipovic, M. Gilfanov,
D. Hatzidimitriou, S. Mereghetti, R. Owen, N. La Palombara, W. Pietsch, R. Sturm, S. Snowden, A. Tiengo
The X-ray Universe 2011, Berlin, Germany, 27-30 June 2011
Historical X-ray studies
Mosaic of ROSAT pointed observations
6x6 degree field (~18 square degrees)
HMXBs
(blue)
SNRs
(greenish)
SSSs
(red)
background AGN
foreground stars
•Einstein IPC: 70 discrete X-ray sources (Wang et al. 1991, Wang & Wu 1992)
•ROSAT PSPC and HRI: 517 sources (PSPC), 121 sources (HRI, 46 additional)
(Haberl et al. 2000, Sasaki et al. 2000)
Diffuse emission 106-107
K (Sasaki et al. 2002)
•ASCA: 106 discrete sources, 17 (8 new) pulsars
(Yokogawa et al. 2003)
•RXTE: monitoring of pulsars (over more than 10 years) (Galache et al. 2008)
Archival XMM-Newton observations of the SMC
EPIC mosaic (2007)
pn in FF/eFF/LW mode
background flare screening
31 useful observations
4 pointings with enhanced bg
typical exposure: 10 – 20 ksec
max exposure @ 1E0102-72.3:
210 ksec (pn)
250 ksec (MOS)
The XMM-Newton survey of the SMC
30 fields (33 pointings) LP in AO8
+ new GO pointings
87 PN + 90 MOS exposures
(noisy MOS CCDs removed,
bg flare screening)
0.2 – 1.0 keV
1.0 – 2.0 keV
2.0 – 4.5 keV
Hα
contour
(SHASSA)
The XMM-Newton survey of the SMC
covered area of 5.5 square degrees
typical exposure: 10 – 30 ksec
for 2/3 of the covered area
max exposure @ 1E0102-72.3:
430 ksec (pn)
590 ksec (MOS)
Catalogue of discrete sources
•95 (-3) observations
•28 of them on 1E0102-72.3
•astrometric
boresight
correction
•source detection simultaneously on 15 images
5 energy bands, 3 EPIC instruments
0.2-0.5 / 0.5-1.0 / 1.0-2.0 / 2.0-4.5 / 4.5-12 keV
•5236 detections after manual screening
(multiple detections in extended regions, oot
events)
•3053 individual sources
2126 are detected once
927 with multiple detections (maximum 34)
Catalogue of 3053 discrete sources
•multiple detections
•detection likelihood
•position
•fluxes (+ upper limits)
•variability
•hardness ratios (spectra for 500 detections)
•correlations with various catalogues
•fx
/fopt
•source classification
•completeness
10-14 erg s-1 cm-2 (0.2-4.5 keV)
4.3x1033 erg s-1 in SMC
Sturm et al. in preparation
See poster F09
Supernova Remnants
Supersoft X-ray sources
Foreground stars
Galaxy Clusters
Background AGN
HMXBs
0.2-1.0 keV
1.0-2.0 keV
2.0-4.5 keV
Bar NE
Bar SW
HMXBs and AGN
z =
z =
An exceptionally large number of HMXBs in the SMC
55 HMXB pulsars
51 with known positions
Many discoveries of X-ray transients with RXTE, ASCA, ROSAT, BeppoSAX
Chandra and XMM-Newton can do spectral and timing analysis down to 1034
erg/s
HMXB population studies
Connection to recent SFH
Metallicity
effects
NS spin period evolution
See next talk by R. Sturm
Highly absorbed sources
Searching for highly absorbed HMXBs
Novara et al. 2011
See poster I07
Source detection
1-3 keV, 3-10 keV
HR selection threshold
NH
> 3x1023
cm-2
SXP25.5
SXP565
SXP293
New Be/X
Old population involving white dwarfs
Best observable in the Magellanic Clouds
Located in outer (older) parts
Classical SSS (stable H burning)
RXJ0058.6-7146 not detected
1E0035.4-7230 not covered (west)
Planetary Nebulae (cooling central star)
1E0056.8-7154 LIN 333, SMP SMC 22
RXJ0059.6-7138 LIN 357, SMP SMC 25
(Mereghetti et al. 2010 – see poster E09)
Symbiotic Systems (cool red giant):
RXJ0059.1-7505 LIN 358 (Kahabka & Haberl 2006)
in pointing to the south
RXJ0048.4-7332 SMC 3 (Sturm et al. 2011)
Faint SSS
RXJ0059.4-7118 foreground object?
RXJ0103.8-7254 not detected
RXJ0050.5-7455 (in pointing to the south)
SSS+Be star (Be/WD X-ray binary)
see following talk by R. Sturm
Supersoft X-ray sources
Sturm et al. 2011, A&A 529, A152
Supersoft X-ray sources: RXJ0048.4-7332 = SMC 3
20 year light curve: highly variable - factor 50
4.5 year period
EPIC-pn spectra:
1) exclude variations caused by changing absorption by neutral gas
2) NH and T constant, L varies 1037 – 6x1038 erg/s
Compton scattering in highly ionised gas?
Eclipse by star and stellar wind
3) NH constant, T varies (L~T4) 24-34 eV
Lbol changes by factor 4.3
variable accretions leads to changes in T?
Supernova Remnants
Concentration in regions of recent star forming activity in SMC bar
van der Heyden et al. 2004
synoptic study of 13 known SNRs
EPIC images
Spectra
Filipovic et al. 2008
three X-ray faint SNRs
one new candidate
Owen et al. 2011
IKT 16
hard point source inside
(see talk session E1)
NE
NE NE
NE
Supernova Remnants
Faint SNRs not covered by van der Heyden at al. (2004)
EPIC X-ray spectra (NEI model)
kT ~ 0.18 keV
kT ~ 0.69 keVkT ~ 0.17 keV
kT ~ 0.19 keV
Filipovic et al. (2008)
Supernova Remnants
enhanced statistics
imroved images
out-of-time events subtracted
detector background subtracted
vignetting corrected
a number of SNRs show larger extent
compare Badenes et al. 2010
new candidates with low surface brightness
and large extent
no SNR at position of IKT 7 (172s Be XRB)
no detection of DEM S130, NS21 and N83C
Haberl
et al. in preparation
F08
F08
F08 F08
F08 = Filipovic
et al. (2008)
Other extended sources – Clusters of galaxies
Mekal model:
NH = 4x1021 cm-2
kT = 1.7 keV
z = 0.07±0.01
Summary
The XMM-Newton survey of the SMC provides a unique data set
for X-ray source population studies.
It complements surveys at other wavelengths.
Supernova remnants
Interaction with their environment
High Mass X-ray binaries
A large population of Be/X-ray binaries in the SMC
Allows statistical studies (SFH, spin periods)
Supersoft
X-ray sources
Discovered as a heterogeneous class of X-ray sources in the MCs
The nature of faint supersoft
sources
Classification of new sources by
X-ray properties (energy spectrum, temporal behaviour)
Information from other wavelength (radio, optical)
Remove foreground (stars) and background (AGN) objects
... Z e ; e.g., Russell & Dopita 1992;Choudhury et al. 2018) make it an ideal target for studying the evolution of both the interstellar medium and stars with well-characterized distances in a more primitive chemical environment than the Milky Way. Consequently, the SMC has been targeted by many surveys covering a wide wavelength range, from X-rays to radio (e.g., Zaritsky et al. 2002;Cutri & 2MASS Team 2004;Kato et al. 2007;Udalski et al. 2008;Ita et al. 2010;Cioni et al. 2011;Gordon et al. 2011;Haberl et al. 2012;Meixner et al. 2013;Joseph et al. 2019). ...
SMC-Last Extracted Photometry
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We present point-source photometry from the Spitzer Space Telescope's final survey of the Small Magellanic Cloud (SMC). We mapped nearly 30 deg ² in two epochs in 2017, with the second extending to early 2018 at 3.6 and 4.5 μ m using the Infrared Array Camera. This survey duplicates the footprint from the SAGE-SMC program in 2008. Together, these surveys cover a nearly 10 yr temporal baseline in the SMC. We performed aperture photometry on the mosaicked maps produced from the new data. We did not use any prior catalogs as inputs for the extractor in order to be sensitive to any moving objects (e.g., foreground brown dwarfs) and other transient phenomena (e.g., cataclysmic variables or FU Ori–type eruptions). We produced a point-source catalog with high-confidence sources for each epoch as well as a combined-epoch catalog. For each epoch and the combined-epoch data, we also produced a more complete archive with lower-confidence sources. All of these data products will be made available to the community at the Infrared Science Archive.
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... In Papers I and II, we primarily included quasi-stellar object (QSO)/AGN templates (hereafter collectively referred to as AGN) as the level of AGN contamination in our sample was unclear. With no comprehensive catalogue of AGN behind the SMC [except for the areas co v ered by, e.g, the XMM -Newton survey (Haberl et al. 2012 ) as well as incomplete spectroscopic samples (e.g. K ozłowski, K ochanek & Udalski 2011 ; Kozłowski et al. 2013 ), we included such templates to not only account for the presence of AGN, but also to provide more fle xibility with re gards to fitting the SEDs. ...
The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – III. The Large Magellanic Cloud
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  • Jun 2022
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We present a map of the total intrinsic reddening across ≃ 90 deg2 of the Large Magellanic Cloud (LMC) derived using optical (ugriz) and near-infrared (IR; YJKs) spectral energy distributions (SEDs) of background galaxies. The reddening map is created from a sample of 222,752 early-type galaxies based on the lephare χ2 minimization SED-fitting routine. We find excellent agreement between the regions of enhanced intrinsic reddening across the central (4 × 4 deg2) region of the LMC and the morphology of the low-level pervasive dust emission as traced by far-IR emission. In addition, we are able to distinguish smaller, isolated enhancements that are coincident with known star-forming regions and the clustering of young stars observed in morphology maps. The level of reddening associated with the molecular ridge south of 30 Doradus is, however, smaller than in the literature reddening maps. The reduced number of galaxies detected in this region, due to high extinction and crowding, may bias our results towards lower reddening values. Our map is consistent with maps derived from red clump stars and from the analysis of the star formation history across the LMC. This study represents one of the first large-scale categorisations of extragalactic sources behind the LMC and as such we provide the lephare outputs for our full sample of ∼ 2.5 million sources.
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... Based on the surveys carried out by Chandra (e.g., Antoniou et al., 2009;Laycock et al., 2010), XMM-Newton (e.g., Haberl et al., 2008Haberl et al., , 2012Haberl & Sturm, 2016), and RXTE (e.g., Laycock et al., 2005;Klus et al., 2013), we have generated a comprehensive time-domain library of the known Be/X-ray binary (Be-XB) pulsars in the Magellanic Clouds, which contains all relevant publicly available observations performed by these satellites up to 2014. We have undertaken the relativistic modeling of the high-energy radiation and pulse profiles of the neutron stars in these systems to constrain the physics and geometry of the accretion flow. ...
X-ray pulsars in nearby irregular galaxies
Thesis
Full-text available
  • Feb 2018
The Small Magellanic Cloud (SMC), Large Magellanic Cloud (LMC) and Irregular Galaxy IC 10 are valuable laboratories to study the physical, temporal and statistical properties of the X-ray pulsar population with multi-satellite observations, in order to probe fundamental physics. The known distance of these galaxies can help us easily categorize the luminosity of the pulsars and their age difference can be helpful for for studying the origin and evolution of compact objects. Therefore, a 17-year archive of 158 XMM-Newton PN, 181 Chandra, and thousands of RXTE observations for the pulsars in the Magellanic Clouds were collected and analyzed. From a sample of 67 SMC pulsars this dissertation generates a suite of products for each pulsar detection: spin period, flux, point source event list, high time-resolution light-curve, pulse-profile, periodogram, and spectrum. The resulting observational library provides a comprehensive view of the SMC pulsars across the accretion-driven X-ray luminosity range of $L_X= 10^{31.5}-10^{38}$~erg~s$^{-1}$. Combining all three satellites, I generated complete histories of the properties for each SMC pulsar. Long-term spin-up/down trends are seen in 28/25 pulsars respectively, pointing to sustained transfer of mass and angular momentum to the neutron star on decadal timescales. The database and pulse profile library are intended to be useful in driving our improved models of neutron star magnetospheres and accretion physics. In addition, 7 out of 207 X-ray point sources are identified as pulsar candidates in the direction of irregular galaxy IC 10 forming a comparison sample with Magellanic Cloud pulsars.
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Radio continuum study of the Large Magellanic Cloud supernova remnant Honeycomb Nebula
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The MeerKAT 1.3 GHz Survey of the Small Magellanic Cloud
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  • Feb 2024
  • MON NOT R ASTRON SOC
We present new radio continuum images and a source catalogue from the MeerKAT survey in the direction of the Small Magellanic Cloud. The observations, at a central frequency of 1.3 GHz across a bandwidth of 0.8 GHz, encompass a field of view ∼7° × 7° and result in images with resolution of 8 arcsec. The median broad-band Stokes I image Root Mean Squared noise value is ∼11 μJy beam−1. The catalogue produced from these images contains 108 330 point sources and 517 compact extended sources. We also describe a UHF (544–1088 MHz) single pointing observation. We report the detection of a new confirmed Supernova Remnant (SNR; MCSNR J0100–7211) with an X-ray magnetar at its centre and 10 new SNR candidates. This is in addition to the detection of 21 previously confirmed SNRs and two previously noted SNR candidates. Our new SNR candidates have typical surface brightness an order of magnitude below those previously known, and on the whole they are larger. The high sensitivity of the MeerKAT survey also enabled us to detect the bright end of the SMC Planetary Nebulae (PNe) sample – point-like radio emission is associated with 38 of 102 optically known PNe, of which 19 are new detections. Lastly, we present the detection of three foreground radio stars amidst 11 circularly polarized sources, and a few examples of morphologically interesting background radio galaxies from which the radio ring galaxy ESO 029–G034 may represent a new type of radio object.
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X-Ray Binaries in External Galaxies
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X-ray appearance of normal galaxies is mainly determined by X-ray binaries powered by accretion onto a neutron star or a stellar mass black hole. Their populations scale with the star-formation rate and stellar mass of the host galaxy, and their X-ray luminosity distributions show a significant split between star-forming and passive galaxies, both facts being consequences of the dichotomy between high- and low-mass X-ray binaries. Metallicity, IMF and stellar age dependencies, and dynamical formation channels add complexity to this picture. The numbers of high-mass X-ray binaries observed in star-forming galaxies indicate quite high probability for a massive star to become an accretion-powered X-ray source once upon its lifetime. This explains the unexpectedly high contribution of X-ray binaries to the cosmic X-ray background, of the order of ∼10%, mostly via X-ray emission of faint star-forming galaxies located at moderate redshifts which may account for the unresolved part of the CXB. Cosmological evolution of the LX −SFR relation can make high-mass X-ray binaries a potentially significant factor in (pre)heating of intergalactic medium in the early Universe.
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The diffuse Fe XXV (6.7 keV) line emission observed in the Galactic ridge is widely accepted to be produced by a superposition of a large number of unresolved X-ray point sources. In the very central degrees of our Galaxy, however, the existence of an extremely hot (~7 keV) diffuse plasma is still under debate. In this work we measure the Fe XXV line emission using all available XMM-Newton observations of the Galactic centre (GC) and inner disc (−10° < ℓ < 10°, −2° < b < 2°). We use recent stellar mass distribution models to estimate the amount of X-ray emission originating from unresolved point sources, and find that within a region of ℓ = ±1° and b = ±0.25° the 6.7keV emission is 1.3–1.5 times in excess of what is expected from unresolved point sources. The excess emission is enhanced towards regions where known supernova remnants are located, suggesting that at least a part of this emission is due to genuine diffuse very hot plasma. If the entire excess is due to very hot plasma, an energy injection rate of at least ~6 × 10 ⁴⁰ erg s ⁻¹ is required, which cannot be provided by the measured supernova explosion rate or past Sgr A * activity alone. However, we find that almost the entire excess we observe can be explained by assuming GC stellar populations with iron abundances ~1.9 times higher than those in the bar/bulge, a value that can be reproduced by fitting diffuse X-ray spectra from the corresponding regions. Even in this case, a leftover X-ray excess is concentrated within ℓ = ±0.3° and b = ±0.15°, corresponding to a thermal energy of ~2 × 10 ⁵² erg, which can be reproduced by the estimated supernova explosion rate in the GC. Finally we discuss a possible connection to the observed GC Fermi -LAT excess.
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Spitzer and Herschel studies of dust in supernova remnants in the Small Magellanic Cloud
Article
  • Apr 2022
  • MON NOT R ASTRON SOC
With the entire Small Magellanic Cloud (SMC) mapped by the Spitzer Space Telescope and Herschel Space Observatory, we were able to search 8–250 $\mu$m images in order to identify infrared (IR) emission associated with SMC supernova remnants (SNRs). A valid detection had to correspond with known X-ray, H α, and radio emission from the SNRs. From the 24 known SNRs, we made five positive detections with another five possible detections. Two detections are associated with pulsars or pulsar wind nebula, and another three detections are part of the extended nebulous emission from the SNRs. We modelled dust emission where fast moving electrons are predicted to collide and heat dust grains which then radiate in IR. With known distance (62.44 ± 0.47 kpc), measured SNR sizes, electron densities, temperatures from X-ray emission as well as hydrogen densities, the modelling of SMC SNRs is straightforward. If the higher range of hydrogen and electron densities were to be accepted, we would expect almost all SMC SNRs to be detected in the IR, at least at 24 $\mu$m, but the actual detection rate is only 25 per cent. One possible and common explanation for this discrepancy is that small grains have been destroyed by the SNRs shockwave. However, within the uncertainties of hydrogen and electron densities, we find that IR dust emission can be explained reasonably well, without invoking dust destruction. There is no conclusive evidence that SNRs destroy swept-up ISM dust.
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Losing a minute every two years: SRG X-ray view of the rapidly accelerating X-ray pulsar SXP 1323
Article
  • Dec 2021
The source SXP 1323 is a peculiar high-mass X-ray binary located in the Small Magellanic Cloud. It is renowned for its rapid spin-up. We investigate for the first time broadband X-ray properties of SXP 1323 as observed by the Mikhail Pavlinsky ART-XC and eROSITA telescopes on board the Spectrum-Roentgen-Gamma observatory. Using ART-XC and eROSITA data, we produced a first broadband 1−20 keV X-ray spectrum and estimated the pulsed fraction box 8 keV. With the addition of archival XMM-Newton observations, we traced the evolution of the spin period of SXP 1323 over the last five years and found that after 2016, the source switched to a linear spin-up with a rate of −29.9 s yr ⁻¹ . The broadband X-ray spectrum is typical for accreting X-ray pulsars. It has a steep power-law index (Γ = −0.15) and an exponential cutoff energy of 5.1 keV. No significant difference between spectra obtained in states with and without pulsations were found.
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The XMM-newton survey of the small magellanic cloud: Discovery of the 11.866s Be/X-ray binary pulsar XMMU J004814.0-732204 (SXP11.87)
Article
Full-text available
  • Mar 2011
Aims: One of the goals of the XMM-Newton survey of the Small Magellanic Cloud is to study the Be/X-ray binary population. During one of our first survey observations, a bright new transient - XMMU J004814.0-732204 - was discovered. Methods: We present the analysis of the EPIC X-ray data, together with optical observations, to investigate the spectral and temporal characteristics of XMMU J004814.0-732204. Results: We found coherent X-ray pulsations in the EPIC data with a period of (11.86642 ± 0.00017) s. The X-ray spectrum can be modelled by an absorbed power law with an indication for a soft excess. Depending on the modelling of the soft X-ray spectrum, the photon index ranges between 0.53 and 0.66. We identify the optical counterpart as a B = 14.9 mag star that was monitored during the MACHO and OGLE-III projects. The optical light curves show regular outbursts by ~0.5 mag in B and R and up to 0.9 mag in I, which repeat on a time scale of about 1000 days. The OGLE-III optical colours of the star are consistent with an early B spectral type. An optical spectrum obtained at the 1.9 m telescope of the South African Astronomical Observatory in December 2009 shows Halpha emission with an equivalent width of 3.5 ± 0.6 Å. Conclusions: The X-ray spectrum and the detection of pulsations suggest that XMMU J004814.0-732204is a new high-mass X-ray binary pulsar in the SMC. The long term variability and the Halpha emission line in the spectrum of the optical counterpart identify it as a Be/X-ray binary system.
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IKT 16: A composite supernova remnant in the Small Magellanic Cloud
Article
Full-text available
  • Jun 2011
Aims: IKT 16 is an X-ray and radio-faint supernova remnant (SNR) in the Small Magellanic Cloud (SMC). A previous X-ray study of this SNR found a hard X-ray source near its centre. Using all available archival and proprietary XMM-Newton data, alongside new multi-frequency radio-continuum surveys and optical observations at Halpha and forbidden [SII] and [OIII] lines, we aim to constrain the properties of the SNR and discover the nature of the hard source within. Methods: We combine XMM-Newton datasets to produce the highest quality X-ray image of IKT 16 to date. We use this, in combination with radio and optical images, to conduct a multi-wavelength morphological analysis of the remnant. We extract separate spectra from the SNR and the bright source near its centre, and conduct spectral fitting of both regions. Results: We find IKT 16 to have a radius of 37 ± 3 pc, with the bright source located 8 ± 2 pc from the centre. This is the largest known SNR in the SMC. The large size of the remnant suggests it is likely in the Sedov-adiabatic phase of evolution. Using a Sedov model to fit the SNR spectrum, we find an electron temperature kT of 1.03 ± 0.12 keV and an age of &ap;14700 yr. The absorption found requires the remnant to be located deep within the SMC. The bright source is fit with a power law with index Gamma = 1.58 ± 0.07, and is associated with diffuse radio emission extending towards the centre of the SNR. We argue that this source is likely to be the neutron star remnant of the supernova explosion, and infer its transverse kick velocity to be 580 ± 100 km s-1. The X-ray and radio properties of this source strongly favour a pulsar wind nebula (PWN) origin. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.
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New XMM-Newton observations of supernova remnants in the Small Magellanic Cloud
Article
Full-text available
  • Jul 2008
Context: A complete overview of the supernova remnant (SNR) population is required to investigate their evolution and interaction with the surrounding interstellar medium in the Small Magellanic Cloud (SMC). Aims: Recent XMM-Newton observations of the SMC cover three known SNRs (DEM S5, SNR B0050-72.8, and SNR B0058-71.8), which are poorly studied and are X-ray faint. We used new multi-frequency radio-continuum surveys and new optical observations at Halpha, [S ii], and [O iii] wavelengths, in combination with the X-ray data, to investigate their properties and to search for new SNRs in the SMC. Methods: We used X-ray source selection criteria and found one SMC object with typical SNR characteristics (HFPK 334), that was initially detected by ROSAT. We analysed the X-ray spectra and present multi-wavelength morphological studies of the three SNRs and the new candidate. Results: Using a non-equilibrium ionisation collisional plasma model, we find temperatures kT around 0.18 keV for the three known remnants and 0.69 keV for the candidate. The low temperature, low surface brightness, and large extent of the three remnants indicates relatively large ages. The emission from the new candidate (HFPK 334) is more centrally peaked and the higher temperature suggests a younger remnant. Our new radio images indicate that a pulsar wind nebulae (PWN) is possibly associated with this object. Conclusions: The SNRs known in the SMC show a variety of morphological structures that are relatively uncorrelated in the different wavelength bands, probably caused by the different conditions in the surrounding medium with which the remnant interacts.
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H I in the Galaxy
Article
Full-text available
  • Nov 2003
An observational review on H I in the Galaxy is presented. Attention is given to observations of interstellar atomic hydrogen from Lyman-alpha and the 21-cm line through indirect tracers such as dust and gamma rays; to what can be learned from such observations; to what the H I sky looks like; and to the state of knowledge in this area and the future prospects. Consideration is also given to results from recent H I investigations that bear on two important areas: the spatial organization of interstellar H I and its vertical distribution in the Galaxy.
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An XMM-Newton survey of M 31
Article
  • May 2005
In an analysis of XMM-Newton archival observations of the bright Local Group spiral galaxy M 31 we study the population of X-ray sources (X-ray binaries, supernova remnants) down to a 0.2-4.5 keV luminosity of 4.4~×~ 1034 . EPIC hardness ratios and optical and radio information are used to distinguish between different source classes. The survey detects 856 sources in an area of 1.24 square degrees. We correlate our sources with earlier M 31 X-ray catalogues and use information from optical, infra-red and radio wavelengths. As sources within M 31 we detect 21 supernova remnants (SNR) and 23 SNR candidates, 18 supersoft source (SSS) candidates, 7 X-ray binaries (XRBs) and 9 XRB candidates, as well as 27 globular cluster sources (GlC) and 10 GlC candidates, which most likely are low mass XRBs within the GlC. Comparison to earlier X-ray surveys reveal transients not detected with XMM-Newton, which add to the number of M 31 XRBs. There are 567 sources classified as hard, which may either be XRBs or Crab-like SNRs in M 31 or background AGN. The number of 44 SNRs and candidates more than doubles the X-ray-detected SNRs. 22 sources are new SNR candidates in M 31 based on X-ray selection criteria. Another SNR candidate may be the first plerion detected outside the Galaxy and the Magellanic Clouds. On the other hand, six sources are foreground stars and 90 foreground star candidates, one is a BL Lac-type active galactic nucleus (AGN) and 36 are AGN candidates, one source coincides with the Local Group galaxy M 32, one with a background galaxy cluster (GCl) and another is a GCl candidate, all sources not connected to M 31.
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Supersoft X-Ray Sources
Article
  • Jan 1996
Observations with X-ray satellite ROSAT over the past 5 years have established supersoft X-ray sources as a new class of objects in our Galaxy and beyond. Optical follow-up observations have revealed the binary nature of several of them. Recent population synthesis calculations have shown that the number of such binaries is expected to be considerably larger than those of the common low- and high-mass X-ray binaries. This book provides the first comprehensive overview of the many recent observational discoveries and theoretical investigations. It describes relations between supersoft sources and other areas in astrophysics. This volume also comprises a complete catalog of presently known supersoft sources including a comprehensive bibliography of observational results.
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Statistics of Galactic Supernova Remnants
Article
  • Aug 2005
  • CHINESE J ASTRON AST
We collected the basic parameters of 231 supernova remnants (SNRs) in our Galaxy, namely, distances (d) from the Sun, linear diameters (D), Galactic heights (Z), estimated ages (t), luminosities (L), surface brightness (Sigma) and flux densities (S1) at 1-GHz frequency and spectral indices (alpha). We tried to find possible correlations between these parameters. As expected, the linear diameters were found to increase with ages for the shell-type remnants, and also to have a tendency to increase with the Galactic heights. Both the surface brightness and luminosity of SNRs at 1-GHz tend to decrease with the linear diameter and with age. No other relations between the parameters were found.
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Abundances of the heavy elements in the Magellanic Clouds. III - Interpretation of results
Article
  • Dec 1991
The observed chemical abundances of the Magellanic Clouds are interpreted in terms of the star formation histories of the Clouds and the relationships between the chemical evolutionary histories of each of the Clouds and with the solar evolution in the Galaxy. It is found that the interstellar medium (ISM) of the LMC has a mean metallicity 0.2 dex lower than the local ISM, and the metallicity of the SMC is 0.6 dex lower. However, the interstellar media of both the Magellanic Clouds and the Galaxy have significantly nonsolar elemental ratios. It is also shown that the stellar carbon abundances in the clouds appear normal, and therefore it is the H II regions that must be overdefficient in this element.
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The planetary nebula systems of the Magellanic Clouds
Article
  • Nov 1978
Very deep blue- and red-sensitive objective-prism plates, taken at the Cerro Tololo Inter-American Observatory for various other programs, have been used to survey both Magellanic Clouds for unresolved emission-line objects that can be classified as confirmed or highly probable planetary nebulae. Listed are 102 (22 new) planetaries in the LMC and 28 (3 new) in the SMC. Emission-line stars and compact H II regions that have been or might be confused with planetary nebulae are also identified. The surface distributions and spectroscopic properties of the planetaries in the two systems are discussed.
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Soft X-Ray Observation of Supernova Remnants in the Small Magellanic Cloud
Article
  • Jan 1983
  • Proc Int Astron Union
The results of Einstein Observatory Imaging Proportional Counter scans of the Small Magellanic Cloud (SMC) to search for supernova remnants (SNR) and structures are reported. The IPC studies focused on H I, H II, and radio emitting regions. Three fields of 20,000 sec exposure each were obtained and revealed 25 sources at a better than 3-sigma confidence level. Six of the sources were positively identified as SNR and six are likely candidates. The luminosity distribution for the candidates is provided to demonstrate the similarity with SNRs discovered in the Large Magellanic Cloud. The results indicate that the proportion of SNRs per unit mass in both clouds is essentially equivalent.
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