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We present a CCD lightcurve for the H impact observed at 948 nm by the
4.2-m William Herschel Telescope at La Palma (Spain). We compare the
results with other lightcurves at visible and near infrared. There
appears to be a common pattern in all the CCD lightcurves: An initial
relative maximum is followed by a relative minimum and another maximum.
C...
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... during the 3 different years. We chose that region by normalizing each image (that is, dividing the data numbers at each pixel by the total counts from Jupiter) taking a Central Meridian scan from each one and comparing the plots. This, to first order, helps us identify the regions with lowest variability. By integrating the reflectivities in Fig. 7 (removing the contribu- tion from the G impact scar), our conclusion is a 5% decrease from 1993 to 1994. This is in agreement with Moreno et al. 1995 who found a small decrease, or no change from 1993 to 1994, using the jovian satellites as a reference, but not the 10% increase suggested by West et al. (1995). We have used a lower ...
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We have obtained visible and near infrared spectra of the Trans Neptunian object 2004 DW, a few days after its discovery, at the Telescopio Nazionale Galileo (TNG). 2004 DW belongs to the plutino dynamical class and has an estimated diameter of about 1600 km, that makes it the largest known object, except Pluto, in the plutino and classical TNO pop...
Citations
... But large r velocities are present, especially in the vanguard. Since this shock comes from the highest velocity material, it is hot, and is most easily seen in the ascending branch of light curves at the shortest wavelengths (McGregor et al. 1996; Ortiz et al. 1997), or in strong spectral bands such as 3.3-µm methane (Dinelli et al. 1997), rather than the long thermal wavelengths (Lagage et al. 1995; Livengood et al. 1995). In our synthetic light curves it produces the 'third precursors' noted by McGregor et al. (1996) and other observers. ...
... 4.3.1), where it accounts for the flare observed to peak near 1000 seconds by several groups (summarized by Ortiz et al. 1997). Model temperatures in the flare shock reach 3000 K. ...
... Several observational groups observed large impacts (L and H) at 0.9 µm, using CCD detector arrays. Ortiz et al. (1997) summarized the observations. Schleicher et al. (1994) obtained the most extensive data, which are re-plotted inFig. 5. The observations as originally published show a baseline drift toward higher intensities at the latest times. They attribute this baseline increase to greater reflectivity of regions surrounding the splashback site, whi ...
We model the plume "splashback" phase of the Shoemaker-Levy 9 (SL9) collisions with Jupiter. We modified the ZEUS-3D hydrodynamic code to include radiative transport in the gray approximation and present validation tests. After initializing with a model Jovian atmosphere, we couple mass and momentum fluxes of SL9 plume material, as calculated by the ballistic Monte Carlo plume model of Paper I of this series. A strong and complex shock structure results. The shock temperatures produced by the model agree well with observations, and the structure and evolution of the modeled shocks account for the appearance of high-excitation molecular line emission after the peak of the continuum light curve. The splashback region cools by radial expansion as well as by radiation. The morphology of our synthetic continuum light curves agrees with observations over a broad wavelength range (0.9-12 μm). Much of the complex structure of these light curves is a natural consequence of the temperature dependence of the Planck function and the plume velocity distribution. A feature of our ballistic plume is a shell of mass at the highest velocities, which we term the "vanguard." Portions of the vanguard ejected on shallow trajectories produce a lateral shock front, whose initial expansion accounts for the "third precursors" seen in the 2 μm light curves of the larger impacts and for hot methane emission at early times observed by Dinelli and coworkers. Continued propagation of this lateral shock approximately reproduces the radii, propagation speed, and centroid positions of the large rings observed at 3-4 μm by McGregor and coworkers. The portion of the vanguard ejected closer to the vertical falls back with high z-component velocities just after maximum light, producing CO emission and the "flare" seen at 0.9 μm. The model also produces secondary maxima ("bounces"), whose amplitudes and periods are in agreement with observations.
... The infalling material deposited its vertical momentum, but continued its horizontal motion for many minutes, sliding on the atmosphere (HAM95, Jessup et al. 2000 ). At wavelengths near 0.9 µm, a brief " flare " appeared and vanished 1000 seconds after impact (Schleicher et al. 1994; Fitzsimmons et al. 1996; Ortiz et al. 1997 ), coincident with spectral observations of hot CO (Meadows & Crisp 1995). In some lightcurves the flare briefly outshone the main event. ...
We model the plumes raised by impacting fragments of comet Shoemaker-Levy 9 to calculate synthetic plume views, atmospheric infall fluxes, and debris patterns. Our plume is a swarm of ballistic particles with one of several mass-velocity distributions (MVDs). The swarm is ejected instantaneously and uniformly into a cone from its apex. On falling to the ejection altitude, particles slide with horizontal deceleration following one of several schemes. The model ignores hydrodynamic and Coriolis effects. Initial conditions come from observations of plume heights and calculated or estimated properties of impactors. We adjust the plume tilt, opening angle, and minimum velocity and choose MVDs and sliding schemes to create impact patterns that match observations. Our best match uses the power-law MVD from the numerical impact model of Zahnle & Mac Low, with velocity cutoffs at 4.5 and 11.8 km s-1, a cone opening angle of 75°, a cone tilt of 30° from vertical, and a sliding constant deceleration of 1.74 m s-2. A mathematically derived feature of Zahnle & Mac Low's published cumulative MVD is a thin shell of mass at the maximum velocity, corresponding to the former atmospheric shock front. This vanguard contains 22% of the mass and 45% of the energy of the plume and accounts for several previously unexplained observations, including the large, expanding ring seen at 3.2 μm by McGregor et al. and the "third precursors" and "flare" seen near 300 and 1000 s, respectively, in the infrared light curves. We present synthetic views of the plumes in flight and after landing and derive infall fluxes of mass, energy, and vertical momentum as a function of time and position on the surface. These fluxes initialize a radiative-hydrodynamic atmosphere model (Paper II of this series) that calculates the thermal and dynamical response of the atmosphere and produces synthetic light curves.
... The Deming and Harrington model identifies the flare at 1000 s after impact (Schleicher et al. 1994, Fitzsimmons et al. 1996a, Ortiz et al. 1997 with the near-simultaneous arrival of the vertically launched portion of the vanguard. Observations of hot CO (Meadows and Crisp 1995) are coincident with the flare and are consistent with the model's peak temperature of 2500 K (but see discussion in Section 8.4.1). ...
Impact circumstances; Atmospheric physics: impact, entry response/blowout, plume flight/landing, plume splash, cooling and dissipation, the HST rings; Atmospheric chemistry: main-event observations, cooling impact sites and modeling, long-term implications; Magnetosphere: observations, explanations, speculations, and models, long-term implications.
The impact of a body of unknown origin with Jupiter in July 2009 (Sánchez-Lavega et al., Astrophys. J. Lett, Vol. 715, L155. 2010) produced an intense perturbation of the planet's atmosphere at the visible levels. The perturbation was caused by dense aerosol material; this strongly absorbing material expanded steadily as it was advected by the local winds. This phenomenon was observed at high spatial resolution by the Hubble Space Telescope in July, August, September and November 2009 with recently installed Wide Field Camera 3. In this work, we present radiative transfer modeling of the observed reflectivity in the near UV (200nm) to near IR (950nm) range. The geometrical and spectral variations of reflectivity elucidate the main particle properties (optical thickness, size, imaginary refractive index) and their temporal evolution. The aerosol particles that formed during the impact have a mean radius of about 1 micron and are located high in the atmosphere (above 10 mbar), in good agreement ith ground-based observations in deep methane absorption bands in the near infrared. The density of this particle layer decreases with time until it approaches that of the pre-impact atmosphere. These results are also discussed in terms of what we know from other impacts in Jupiter (1994's SL9 event and 2010's bolide). Acknowledgements: SPH, ASL and RH are supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.
We present the first results of a search for bright flashes associated
to impacts of meteoroids on the surface of the night side of the Moon.
We have analysed 13 sets of images of a (2.9+/-0.3) 10(6) -km(2) -wide
area on the Moon's night side, totaling 4.3 h of observations. No impact
events radiating an amount of energy higher than 5x 10(6) J have been
detected. Five fainter events (E < 2.5x 10(6) J) have been detected,
but they are not confidently identified as impact-related, and might be
due to experimental problems. This rate of events would imply an influx
of 4800 +/- 500 meteoroids per day onto the Earth, with meteoroid masses
of uncertain value, but larger than 0.01 kg. The direct CCD imaging
technique that we have used is a potential new tool to asses the
population of those meteoroids in the vicinity of the Earth whose masses
and velocities are such that the radiated energy upon impact is higher
than 5x 10(6) J, our threshold for 100% confident detection. The
technique can be improved substantially to detect fainter impacts and
might provide unique data for the 1999 Leonid meteor shower.
