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Register a new userComet C/2011 J2 (LINEAR): Photometry and Stellar transit
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We present results of two-year photometric monitoring of Comet C/2011 J2 (LINEAR) that spans the time period from February 2013 through December 2014, before and after perihelion passage. The observations were conducted with broadband R filter. Analysis of observations of Comet C/2011 J2 (LINEAR) allows estimating the nucleus radius as function of geometric albedo and phase-darkening coefficient. Furthermore, our observations showed split of the comet. Fragment (B) additional to the primary C/2011 J2 nucleus was unambiguously detected; relative velocity is estimated to be near 0.17 /day. We derive the Afrho parameter and estimate the dust production rate in Comet C/2011 J2 (LINEAR) over the entire run of observations. We found a noticeable increase in Afrho parameter between September 18, 2014 and November 5, 2014, epoch when the nucleus presumably got split. On September 28, 2014, we observed a transit of the 16-magnitude star (USNO-A2 1275-18299027) near nucleus of the Comet C/2011 J2 (LINEAR). We retrieve the optical depth of the coma 0.034. The filling factor f that corresponds to such optical depth is in good quantitative agreement with the value that can be derived from the Afrho parameter under reasonable assumption on geometric albedo of cometary dust.
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Dynamically new comet C/2011 L4 (PanSTARRS) is one of the brightest comets since the great comet C/1995 O1 (Hale-Bopp). Here, we present our multi-wavelength observations of C/2011 L4 during its in-bound passage to the inner Solar system. A strong absorption band of water ice at 2.0 $mu$m was detected in the near infrared spectra, taken with the 8-m Gemini-North and 3-m IRTF telescopes. The companion 1.5 $mu$m band of water ice, however, was not observed. Spectral modeling show that the absence of the 1.5 $mu$m feature can be explained by the presence of sub-micron-sized fine ice grains. No gas lines (i.e. CN, HCN or CO) were observed pre-perihelion either in the optical or in the sub-millimeter. 3-$sigma$ upper limits to the CN and CO production rates were derived. The comet exhibited a very strong continuum in the optical and its slope seemed to become redder as the comet approached the Sun. Our observations suggest that C/2011 L4 is an unusually dust-rich comet with a dust-to-gas mass ratio $>$ 4.
We present the results of photometry, linear spectropolarimetry, and imaging circular polarimetry ofcomet C/2009 P1 (Garradd) performed at the 6-m telescope BTA of the Special Astrophysical Observatory(Russia) equipped by the multi-mode focal reducer SCORPIO-2. The comet was observed at two epochspost-perihelion: on February 2-14, 2012 at r=1.6 au and {alpha}=36 {deg}; and on April 14-21, 2012 at r=2.2 au and {alpha}=27 deg. The spatial maps of the relative intensity and circular polarization as well as the spectral distribution of linear polarization are presented. There were two features (dust and gas tails) orientedin the solar and antisolar directions on February 2 and 14 that allowed us to determine rotation periodof the nucleus as 11.1 hours. We detected emissions of C2 , C3 , CN, CH, NH2 molecules as well as CO+ and H2O+ ions, along with a high level of the dust continuum. On February 2, the degree of linear polarization in the continuum, within the wavelength range of 0.67-0.68 {mu}m, was about 5% in the near-nucleus region up to near 6000 km and decreased to about 3% at near 40,000 km. The left-handed (negative) circular polarization at the level approximately from -0.06% to -0.4% was observed at the distances up to 3*10^4 km from the nucleus on February 14 and April 21, respectively.
We analyze the dust environment of the distant comet C/2014 A4 (SONEAR), with a perihelion distance near 4.1~au, using comprehensive observations obtained by different methods. We present an analysis of spectroscopy, photometry, and polarimetry of comet C/2014 A4 (SONEAR), which were performed on November 5~--~7, 2015, when its heliocentric distance was 4.2~au and phase angle was 4.7$^circ$. Long-slit spectra and photometric and linear polarimetric images were obtained using the focal reducer SCORPIO-2 attached to the prime focus of the 6-m telescope BTA (SAO RAS, Russia). We simulated the behavior of color and polarization in the coma presenting the cometary dust as a set of polydisperse polyshapes rough spheroids. No emissions were detected in the 3800~--~7200~$AA$ wavelength range. The continuum showed a reddening effect with the normalized gradient of reflectivity 21.6$pm$0.2% per 1000~$AA$ within the 4650~--~6200~$AA$ wavelength region. The fan-like structure in the sunward hemisphere was detected. The radial profiles of surface brightness differ for r-sdss and g-sdss filters, indicating predominance of submicron and micron-sized particles in cometary coma. The dust color (g--r) varies from 0.75$ pm $0.05$^m$ to 0.45$ pm $0.06$^m$ along the tail. For aperture radius near 20~000~km, the dust productions in various filters were estimated as $Afrho $~=~680$pm$18~cm (r-sdss) and 887$ pm $16~cm (g-sdss). The polarization map showed spatial variations of polarization over the coma from about --3% near the nucleus to --8% at cometocentric distance about 150~000~km. Our simulations show that the dust particles were dominated (or covered) by ice and tholin-like organics. Spatial changes in the color and polarization can be explained by particle fragmentation.
C/2002 CE$_{10}$ is an object in a retrograde elliptical orbit with Tisserand parameter $-0.853$ indicating a likely origin in the Oort Cloud. It appears to be a rather inactive comet since no coma and only a very weak tail was detected during the past perihelion passage. We present multi-color optical photometry, lightcurve and thermal mid-IR observations of the asteroidal comet. textcolor{blue}{ With the photometric analysis in $BVRI$, the surface color is found to be redder than asteroids, corresponding to cometary nuclei and TNOs/Centaurs. The time-resolved differential photometry supports a rotation period of 8.19$pm$0.05 h. The effective diameter and the geometric albedo are 17.9$pm$0.9 km and 0.03$pm$0.01, respectively, indicating a very dark reflectance of the surface. The dark and redder surface color of C/2002 CE$_{10}$ may be attribute to devolatilized material by surface aging suffered from the irradiation by cosmic rays or from impact by dust particles in the Oort Cloud. Alternatively, C/2002 CE$_{10}$ was formed of very dark refractory material originally like a rocky planetesimal. In both cases, this object lacks ices (on the surface at least). The dynamical and known physical characteristics of C/2002 CE$_{10}$ are best compatible with those of the Damocloids population in the Solar System, that appear to be exhaust cometary nucleus in Halley-type orbits. The study of physical properties of rocky Oort cloud objects may give us a key for the formation of the Oort cloud and the solar system.
We present an analysis of the photometric and spectroscopic observations of the split comet C/2019 Y4 (ATLAS). Observations were carried out on the 14th and 16th of April 2020 when the heliocentric distances of the comet were 1.212 and 1.174 au, its geocentric distances 0.998 and 0.991 au, and the phase angle 52.9{deg} and 54.5{deg}, respectively. The comet was observed with the 6-m BTA telescope of the Special Astrophysical Observatory (Russia) with the SCORPIO-2 multi-mode focal reducer. The narrow-band BC and RC cometary filters in the continuum were used. We identified numerous emissions of the CN, C2, C3, and NH2 molecules within the range of 3750-7100 {AA}. The C2/CN and C3/CN production rate ratios coincide with those of typical comets. Four fragments belonging to the coma were detected in both observational runs. We compared and analyzed temporal variations of the visual magnitudes, gas productivity, and dust colour. Based on our dynamical investigation of the orbits of comets C/1844 Y1 (Great comet) and C/2019 Y4 (ATLAS), we can claim that, with high probability, two comets do not have a common progenitor.
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