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تسجيل مستخدم جديدPhotometric investigations of distant comets C/2002 VQ94 (LINEAR) and 29P/Schwassmann-Wachmann-1
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We present an analysis of the results of photometric investigations of two distant comets, C/2002 VQ94 (LINEAR) and 29P/Schwassmann-Wachmann 1, obtained with the 6m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The comets under study demonstrate sufficient activity out of the zone of water ice sublimation (at heliocentric distances longer than 5 AU). In the spectra of the investigated comets, we found the CO+ and N2+ emission. The presence of this emission may say that the comets were formed in the outer parts of the Solar System, in a protoplanetary cloud at a temperature <=25 K. We found that the photometric maximum of the ionosphere (in the CO+ filter) of the comet C/2002 VQ94 (LINEAR) is shifted relative to the photometric center of the dust coma by 1.4 arcsec (7.44*10^3 km) in the direction deflected by 63 deg from the direction to the Sun. Using special filters to process the images, we picked out active structures (jets) in the dust coma of the 29P/Schwassmann-Wachmann 1 comet.
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We investigated three comets, which are active at large heliocentric distances, using observations obtained at the 6-m BTA telescope (SAO RAS, Russia) in the photometric mode of the focal reducer SCORPIO. The three comets, 29P/Schwassmann-Wachmann 1,
C/2003 WT42 (LINEAR), and C/2002 VQ94 (LINEAR), were observed after their perihelion passages at heliocentric distances between 5.5 and 7.08 AU. The dust production rates in terms of Afrho was measured for these comets. Using the retrieved values, an average dust production rate was derived under different model assumptions. A tentative calculation of the total mass loss of the comet nucleus within a certain observation period was executed. We calculated the corresponding thickness of the depleted uppermost layer where high-volatile ices completely sublimated. The results obtained in our study strongly support the idea that the observed activity of Comet SW1 requires a permanent demolition of the upper surface layers.
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umber of TNO test particles that enter the Centaur population, we have identified a short-lived dynamical Gateway, a temporary low-eccentricity region exterior to Jupiter through which the majority of JFCs pass. We apply an observationally based size distribution function to the known Centaur population and obtain an estimated Gateway region population. We then apply an empirical fading law to the rate of incoming JFCs implied by the the Gateway region residence times. Our derived estimates are consistent with observed population numbers for the JFC and Gateway populations. Currently, the most notable occupant of the Gateway region is 29P/Schwassmann-Wachmann 1 (SW1), a highly active, regularly outbursting Centaur. SW1s present-day, very-low-eccentricity orbit was established after a 1975 Jupiter conjunction and will persist until a 2038 Jupiter conjunction doubles its eccentricity and pushes its semi-major axis out to its current aphelion. Subsequent evolution will likely drive SW1s orbit out of the Gateway region, perhaps becoming one of the largest JFCs in recorded history. The JFC Gateway region coincides with a heliocentric distance range where the activity of observed cometary bodies increases significantly. SW1s activity may be typical of the early evolutionary processing experienced by most JFCs. Thus, the Gateway region, and its most notable occupant SW1, are critical to both the dynamical and physical transition between Centaurs and JFCs.
We carried out photometric and spectroscopic observations of comet 29P/ Schwassmann-Wachmann 1 at the SOAR 4.1-meter telescope (Chile) on August 12, 2016. This paper presents the results of only spectroscopic analysis. The spectra revealed presence o
f CO$^+$ and N$_2^+$ emissions in the cometary coma at a distance of 5.9 AU from the Sun. The ratio [N$_2^+$]/[CO$^+$] within the projected slit seems to be 0.01. We have also estimated spectral gradient value for the comet.
We present analyses of Spitzer observations of 29P/Schwassmann-Wachmann 1 using 16 $mu$m IRS blue peak-up (PU) and 24 $mu$m and 70 $mu$m MIPS images obtained on UT 2003 November 23 and 24 that characterize the Centaurs large-grain (10-100 $mu$m) dust
coma during a time of non-outbursting quiescent activity. Estimates of $epsilon f rho$ for each band (16 $mu$m (2600 $pm$ 43 cm), 24 $mu$m (5800 $pm$ 63 cm), and 70 $mu$m (1800 $pm$ 900 cm)) follow the trend between nucleus size vs. $epsilon f rho$ that was observed for the WISE/NEOWISE comet ensemble. A coma model was used to derive a dust production rate in the range of 50-100 kg/s. For the first time, a color temperature map of SW1s coma was constructed using the 16 $mu$m and 24 $mu$m imaging data. With peaks at $sim$ 140K, this map implies that coma water ice grains should be slowly sublimating and producing water gas in the coma. We analyzed the persistent 24 $mu$m wing (a curved southwestern coma) feature at 352,000 km (90$$) from the nucleus attributed by Stansberry et al. (2004) to nucleus rotation and instead propose that it is largely created by solar radiation pressure and gravity acting on micron sized grains. We performed coma removal to the 16 $mu$m PU image in order to refine the nucleus emitted thermal flux. A new application of the Near Earth Asteroid Thermal Model (NEATM; Harris 1998) at five wavelengths (5.730 $mu$m, 7.873 $mu$m, 15.80 $mu$m, 23.68 $mu$m, and 71.42 $mu$m) was then used to refine SW1s effective radius measurement to $R = 32.3 pm 3.1$ km and infrared beaming parameter to $eta = 1.1 pm 0.2$, respectively.
The results of the photometric observations of comet 29P/Schwassmann-Wachmann 1 are analyzed. The comet demonstrates substantial activity at heliocentric distances larger than 5 AU, outside the water ice sublimation zone. The CCD images of the comet
were obtained in wideband R filters at the 6m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) and at the 2m telescope of the Peak Terskol Observatory. The processing of the images with special digital filters allowed the active structures (jets) to be distinguished in the dust coma of the comet. With the cross correlation method, the rotation period of the cometary nucleus was determined as 12.1 and 11.7 days for the observations taken in December 2008, and February 2009, respectively. The probable causes of the difference in the estimates of the rotation period of the cometary nucleus obtained by differen authors are discussed.
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