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61. TRAPPIST monitoring of comet C/2012 F6 (Lemmon)
ID:
ivo://CDS.VizieR/J/A+A/574/A38
Title:
TRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Short Name:
J/A+A/574/A38
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of the long-term narrowband photometry and imaging monitoring of comet C/2012 F6 (Lemmon) with the robotic TRAPPIST telescope (La Silla observatory). Observations covered 52 nights pre- and post-perihelion between December 11, 2012 and June 11, 2013. We followed the evolution of the OH, NH, CN, C_3_ and C_2_ production rates computed with the Haser model as well as the evolution of the A({theta})f_{rho}_ parameter as a proxy for the dust production. All five gas species display similar slopes for the heliocentric dependence. An asymmetry about perihelion is observed, the rate of brightening being steeper than the rate of fading. The chemical composition of the comet's coma is changing slightly along the orbit: the relative abundance of C_2_ to CN is decreasing for heliocentric distances larger than 1.4AU while the C_3_ to CN ratio is constant during our observations. The behavior of the dust is different from that of the gas, the slope of the heliocentric dependence becoming steeper in early February, correlated to a change of the visual lightcurve slope. However, the dust color does not vary during the observations. The application of several enhancement techniques on the images revealed structures in the CN, C3 and C2 images. These features imply the existence of one or several active zone(s) on the comet nucleus. The shape of the structures is similar in those three filters and changes from a roughly hourglass shape in December and January to a corkscrew shape in February and March. The structures in the continuum filters (sampling the dust) are not correlated to those observed for the gas. During several full nights in February, we observed changes in the CN and C2 structures repeating periodically due to the nucleus rotation, our derived rotational period being of 9.52+/-0.05 hours.
62. Unidentified cometary emission lines
ID:
ivo://CDS.VizieR/J/PAZh/30/946
Title:
Unidentified cometary emission lines
Short Name:
J/PAZh/30/946
Date:
21 Oct 2021
Publisher:
CDS
Description:
We discuss the possible nature of unidentified cometary emission lines. We propose a model of the ice particles in cometary halos as a mixture of frozen polycyclic aromatic hydrocarbons (PAHs) and acyclic hydrocarbons. We describe the general properties of frozen hydrocarbon particles (FHPs) and suggest interpreting some of the unidentified cometary emission lines as the photoluminescence of FHPs. We compare the position of quasi-lines in the spectrum of Comet 122P/de Vico with the position of quasi-lines in the photoluminescence spectrum of PAHs that were dissolved in acyclic hydrocarbons at a temperature of 77K and that constituted a polycrystalline solution. We estimated the detectability of FHP photoluminescence in cometary spectra.
63. VOEvent meteor shower service
ID:
ivo://padc.obspm.planeto/meteor_showers/q/epn_core
Title:
VOEvent meteor shower service
Short Name:
Meteor Showers
Date:
16 Jul 2024 13:55:03
Publisher:
Paris Astronomical Data Centre
Description:
The ephemeris were produced by simulating the ejection of meteoroids from the sunlit hemisphere of cometary nuclei, typically from 0 to 3 au, followed by the propagation of orbits of meteoroids in the Solar System, taking into account the gravity of the Sun, the 8 planets, Pluto, and the Moon, as well as the radiation pressure and the Poynting-Robertson drag. Note that asteroid parent bodies were considered as active (i.e. comet-like bodies) even if they are not active today. The showers are predicted when a planet enters a large enough set of meteoroids, at a distance less than typically 0.01 au. See Vaubaillon J., Colas F., Jorda L. 2005 A new method to predict meteor showers. I. Description of the model, Astronomy and Astrophysics, Volume 439/2 p.751-760, as well as: Vaubaillon J. 2017 A confidence index for forecasting of meteor showers, Planetary and Space Science, Volume 143 p.78-82
64. WINERED CN-red band emission in comet C/2013 R1
ID:
ivo://CDS.VizieR/J/AJ/154/45
Title:
WINERED CN-red band emission in comet C/2013 R1
Short Name:
J/AJ/154/45
Date:
21 Oct 2021
Publisher:
CDS
Description:
Although high-resolution spectra of the CN red-system band are considered useful in cometary sciences, e.g., in the study of isotopic ratios of carbon and nitrogen in cometary volatiles, there have been few reports to date due to the lack of high-resolution (R={lambda}/{Delta}{lambda}>20000) spectrographs in the near-infrared region around ~1 {mu}m. Here, we present the high-resolution emission spectrum of the CN red-system band in comet C/2013 R1 (Lovejoy), acquired by the near-infrared high-resolution spectrograph WINERED mounted on the 1.3 m Araki telescope at the Koyama Astronomical Observatory, Kyoto, Japan. We applied our fluorescence excitation models for CN, based on modern spectroscopic studies, to the observed spectrum of comet C/2013 R1 (Lovejoy) to search for CN isotopologues (^13^C^14^N and ^12^C^15^N). We used a CN fluorescence excitation model involving both a "pure" fluorescence excitation model for the outer coma and a "fully collisional" fluorescence excitation model for the inner coma region. Our emission model could reproduce the observed ^12^C^14^N red-system band of comet C/2013 R1 (Lovejoy). The derived mixing ratio between the two excitation models was 0.94(+0.02/-0.03):0.06(+0.03/-0.02), corresponding to the radius of the collision-dominant region of ~800-1600 km from the nucleus. No isotopologues were detected. The observed spectrum is consistent, within error, with previous estimates in comets of ^12^C/^13^C (~90) and ^14^N/^15^N (~150).
65. WISE/NEOWISE observations of comets
ID:
ivo://CDS.VizieR/J/AJ/154/53
Title:
WISE/NEOWISE observations of comets
Short Name:
J/AJ/154/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use NEOWISE data from the four-band and three-band cryogenic phases of the Wide-field Infrared Survey Explorer mission to constrain size distributions of the comet populations and debias measurements of the short- and long-period comet (LPC) populations. We find that the fit to the debiased LPC population yields a cumulative size-frequency distribution (SFD) power-law slope ({beta}) of -1.0+/-0.1, while the debiased Jupiter-family comet (JFC) SFD has a steeper slope with {beta}=-2.3+/-0.2. The JFCs in our debiased sample yielded a mean nucleus size of 1.3km in diameter, while the LPCs' mean size is roughly twice as large, 2.1km, yielding mean size ratios (<D_LPC_>/<D_JFC_>) that differ by a factor of 1.6. Over the course of the 8 months of the survey, our results indicate that the number of LPCs passing within 1.5 au are a factor of several higher than previous estimates, while JFCs are within the previous range of estimates of a few thousand down to sizes near 1.3km in diameter. Finally, we also observe evidence for structure in the orbital distribution of LPCs, with an overdensity of comets clustered near 110{deg} inclination and perihelion near 2.9 au that is not attributable to observational bias.