- ID:
- ivo://CDS.VizieR/J/ApJ/793/50
- Title:
- Observed light curve of (3200) Phaethon
- Short Name:
- J/ApJ/793/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (3200) Phaethon exhibits both comet- and asteroid-like properties, suggesting it could be a rare transitional object such as a dormant comet or previously volatile-rich asteroid. This justifies detailed study of (3200) Phaethon's physical properties as a better understanding of asteroid-comet transition objects can provide insight into minor body evolution. We therefore acquired time series photometry of (3200) Phaethon over 15 nights from 1994 to 2013, primarily using the Tektronix 2048x2048 pixel CCD on the University of Hawaii 2.2 m telescope. We utilized light curve inversion to (1) refine (3200) Phaethon's rotational period to P=3.6032+/-0.0008 hr; (2) estimate a rotational pole orientation of {lambda}=+85{deg}+/-13{deg} and {beta}=-20{deg}+/-10{deg}; and (3) derive a shape model. We also used our extensive light curve data set to estimate the slope parameter of (3200) Phaethon's phase curve as G~0.06, consistent with C-type asteroids. We discuss how this highly oblique pole orientation with a negative ecliptic latitude supports previous evidence for (3200) Phaethon's origin in the inner main asteroid belt as well as the potential for deeply buried volatiles fueling impulsive yet rare cometary outbursts.
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- ID:
- ivo://CDS.VizieR/J/ApJ/889/L30
- Title:
- Opt. spectra of the interstellar object 2I/Borisov
- Short Name:
- J/ApJ/889/L30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 2I/Borisov is the first-ever observed interstellar comet (and the second detected interstellar object (ISO)). It was discovered on 2019 August 30 and has a heliocentric orbital eccentricity of ~3.35, corresponding to a hyperbolic orbit that is unbound to the Sun. Given that it is an ISO, it is of interest to compare its properties-such as composition and activity-with the comets in our solar system. This study reports low-resolution optical spectra of 2I/Borisov. The spectra were obtained by the MDM Observatory Hiltner 2.4m telescope/Ohio State Multi-Object Spectrograph (on 2019 October 31.5 and November 4.5, UT). The wavelength coverage spanned from 3700 to 9200{AA}. The dust continuum reflectance spectra of 2I/Borisov show that the spectral slope is steeper in the blue end of the spectrum (compared to the red). The spectra of 2I/Borisov clearly show CN emission at 3880{AA}, as well as C2 emission at both 4750 and 5150{AA}. Using a Haser model to covert the observed fluxes into estimates for the molecular production rates, we find Q(CN)=2.4+/-0.2x10^24^s^-1^, and Q(C_2_)=(5.5+/-0.4)x10^23^s^-1^ at the heliocentric distance of 2.145au. Our Q(CN) estimate is consistent with contemporaneous observations, and the Q(C_2_) estimate is generally below the upper limits of previous studies. We derived the ratio Q(C_2_)/Q(CN)=0.2+/-0.1, which indicates that 2I/Borisov is depleted in carbon-chain species, but is not empty. This feature is not rare for the comets in our solar system, especially in the class of Jupiter-family comets.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/L38
- Title:
- Opt. spectroscopic investigations of 2I/Borisov
- Short Name:
- J/ApJ/889/L38
- Date:
- 17 Jan 2022 00:14:14
- Publisher:
- CDS
- Description:
- The composition of comets in the solar system comes in multiple groups thought to encode information about their formation in different regions of the outer protosolar disk. The recent discovery of the second interstellar object, 2I/Borisov, allows for spectroscopic investigations into its gas content and a preliminary classification of it within the solar system comet taxonomies to test the applicability of planetesimal formation models to other stellar systems. We present spectroscopic and imaging observations from 2019 September 20 through October 26 from the Bok, MMT telescope (formerly the Multiple Mirror Telescope, Mount Hopkins, Arizona), and Large Binocular Telescopes. We identify CN in the comet's spectrum and set precise upper limits on the abundance of C_2_ on all dates in October. We use a Haser model to convert our integrated fluxes to production rates and find Q(CN)=(1.1-1.9)*10^24^mols/s increasing over 2019 October 1 to 26, consistent with contemporaneous observations. We set our lowest upper limit on a C_2_ production rate, Q(C_2_)<1.6*10^23^mols/s on 2019 October 10. The measured upper limit ratio for that date Q(C_2_)/Q(CN)<0.1 indicates that 2I/Borisov is strongly in the (carbon-chain) "depleted" taxonomic group if there is any C_2_ production at all. Most "depleted" comets are Jupiter-family comets (JFCs), perhaps indicating a similarity in formation conditions between the most depleted of the JFCs and 2I/Borisov. More work is needed to understand the applicability of our knowledge of solar system comet taxonomies onto interstellar objects and we discuss future work that could help to clarify the usefulness of the approach.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A12
- Title:
- 67P/Churyumov-Gerasimenko R-band light curve
- Short Name:
- J/A+A/548/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Comet 67P/Churyumov-Gerasimenko is the target of the European Space Agency Rosetta spacecraft rendez-vous mission. Detailed physical characteristation of the comet before arrival is important for mission planning as well as providing a test bed for ground-based observing and data-analysis methods. To conduct a long-term observational programme to characterize the physical properties of the nucleus of the comet, via ground-based optical photometry, and to combine our new data with all available nucleus data from the literature. We applied aperture photometry techniques on our imaging data and combined the extracted rotational lightcurves with data from the literature. Optical lightcurve inversion techniques were applied to constrain the spin state of the nucleus and its broad shape. We performed a detailed surface thermal analysis with the shape model and optical photometry by incorporating both into the new Advanced Thermophysical Model (ATPM), along with all available Spitzer 8-24um thermal-IR flux measurements from the literature. A convex triangular-facet shape model was determined with axial ratios b/a=1.239 and c/a=0.819. These values can vary by as much as 7% in each axis and still result in a statistically significant fit to the observational data. Our best spin state solution has P_sid_=12.76137+/-0.00006 hrs, and a rotational pole orientated at Ecliptic coordinates lambda=78{deg}(+/-10{deg}), beta=+58{deg}(+/-10{deg}). The nucleus phase darkening behaviour was measured and best characterized using the IAU HG system. Best fit parameters are: G=0.11+/-0.12 and H_R(1,1,0)_=15.31+/-0.07. Our shape model combined with the ATPM can satisfactorily reconcile all optical and thermal-IR data, with the fit to the Spitzer 24um data taken in February 2004 being exceptionally good. We derive a range of mutually-consistent physical parameters for each thermal-IR data set, including effective radius, geometric albedo, surface thermal inertia and roughness fraction. The overall nucleus dimensions are well constrained and strongly imply a broad nucleus shape more akin to comet 9P/Tempel 1, rather than the highly elongated or `bilobed' nuclei seen for comets 103P/Hartley 2 or 8P/Tuttle. The derived low thermal inertia of <15J/m^2^/K/s^1/2^ is comparable with that measured for other comets scaled to similar heliocentric distances, and implies a surface regolith finer than lunar surface material.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A113
- Title:
- 67P/Churyumov-Gerasimenko R-band light curve
- Short Name:
- J/A+A/527/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Jupiter family comet (JFC) 67P/Churyumov-Gerasimenko is the target of the ESA's ROSETTA mission. Observational campaigns and theoretical investigations were performed to characterise 67P/C-G in terms of nucleus properties (e.g. size, surface colors, rotational period), gas and dust production, and plasma environment in preparation for the rendezvous with the spacecraft; however, there are still open questions which need to be addressed. Our observations of 67P/C-G are important not only for good planning of the rendezvous of the ROSETTA spacecraft with 67P/C-G, but also provide valuable information on the basic physical properties of the nuclei of JFCs at large heliocentric distances. Moreover, this information will also help to identify to what extent 67P/C-G is a typical JFC.
- ID:
- ivo://CDS.VizieR/J/A+A/374/712
- Title:
- Photometric observations of comets
- Short Name:
- J/A+A/374/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD VRc photometry of 3 distant active comets visible in July, 2000. Time-series data cover 16 hours. Data were obtained with the 1.23m telescope of the German-Spanish Astronomical Centre, Calar Alto.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/151
- Title:
- Properties of asteroids in comet-like orbits
- Short Name:
- J/ApJ/789/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the population of asteroids in comet-like orbits using available asteroid size and albedo catalogs of data taken with the Infrared Astronomical Satellite, AKARI, and the Wide-field Infrared Survey Explorer on the basis of their orbital properties (i.e., the Tisserand parameter with respect to Jupiter, T_J_, and the aphelion distance, Q). We found that (1) there are 123 asteroids in comet-like orbits by our criteria (i.e., Q > 4.5 AU and T_J_< 3), (2) 80% of them have low albedo, p_v_< 0.1, consistent with comet nuclei, (3) the low-albedo objects among them have a size distribution shallower than that of active comet nuclei, that is, the power index of the cumulative size distribution is around 1.1, and (4) unexpectedly, a considerable number (i.e., 25 by our criteria) of asteroids in comet-like orbits have high albedo, p_v_> 0.1. We noticed that such high-albedo objects mostly consist of small (D < 3 km) bodies distributed in near-Earth space (with perihelion distance of q < 1.3 AU). We suggest that such high-albedo, small objects were susceptible to the Yarkovsky effect and drifted into comet-like orbits via chaotic resonances with planets.
- ID:
- ivo://CDS.VizieR/J/AJ/154/196
- Title:
- Properties of comet 49P/Arend-Rigaux, 1984-2012
- Short Name:
- J/AJ/154/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyzed images of comet 49P/Arend-Rigaux on 33 nights between 2012 January and May and obtained R-band lightcurves of the nucleus. Through usual phasing of the data, we found a double-peaked lightcurve having a synodic rotation period of 13.450+/-0.005 hr. Similarly, phase dispersion minimization and the Lomb-Scargle method both revealed rotation periods of 13.452 hr. Throughout the 2011/2012 apparition, the rotation period was found to increase by a small amount, consistent with a retrograde rotation of the nucleus. We also reanalyzed the publicly available data from the 1984/1985 apparition by applying the same techniques, finding a rotation period of 13.45+/-0.01 hr. Based on these findings, we show that the change in rotation period is less than 14 s per apparition. Furthermore, the amplitudes of the lightcurves from the two apparitions are comparable, to within reasonable errors, even though the viewing geometries differ, implying that we are seeing the comet at a similar sub-Earth latitude. We detected the presence of a short-term jet-like feature in 2012 March, which appears to have been created by a short-duration burst of activity on March 15. Production rates obtained in 2004/2005, along with reanalysis of the previous results from 1984/1985, imply a strong seasonal effect and a very steep fall-off after perihelion. This, in turn, implies that a single source region, rather than leakage from the entire nucleus, dominates activity.
- ID:
- ivo://CDS.VizieR/J/AJ/157/186
- Title:
- r'-band photometry of comet 96P/Machholz 1
- Short Name:
- J/AJ/157/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed comet 96P/Machholz 1 on a total of nine nights before and after perihelion during its 2017/2018 apparition. Both its unusually small perihelion distance and the observed fragmentation during multiple apparitions make 96P an object of great interest. Our observations show no evidence of a detectable dust coma, implying that we are observing a bare nucleus at distances ranging from 2.3 to 3.8 au. Based on this assumption, we calculated its color and found average values of g'-r'=0.50+/-0.04, r'-i'=0.17+/-0.03, and i'-z'=0.06+/-0.04. These are notably more blue than those of the nuclei of other Jupiter-family and long-period comets. Furthermore, assuming a bare nucleus, we found an equivalent nuclear radius of 3.4+/-0.2 km with an axial ratio of at least 1.6+/-0.1. The lightcurve clearly displays one large peak, one broad flat peak, and two distinct troughs, with a clear asymmetry that suggests that the shape of the nucleus deviates from that of a simple triaxial ellipsoid. This asymmetry in the lightcurve allowed us to constrain the nuclear rotation period to 4.10+/-0.03 hr and 4.096+/-0.002 hr before and after perihelion, respectively. Within the uncertainties, 96P's rotation period does not appear to have changed throughout the apparition, and we conclude a maximum possible change in rotation period of 130 s. The observed properties were compared to those of comet 322P and interstellar object 1I/'Oumuamua in an attempt to study the effects of close perihelion passages on cometary surfaces and their internal structure and the potential interstellar origin of 96P.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/S138
- Title:
- Robotic view of 67P perihelion
- Short Name:
- J/MNRAS/462/S138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Around the time of its perihelion passage, the observability of 67P/Churyumov-Gerasimenko from Earth was limited to very short windows each morning from any given site, due to the low solar elongation of the comet. The peak in the comet's activity was therefore difficult to observe with conventionally scheduled telescopes, but was possible where service/queue-scheduled mode was possible, and with robotic telescopes. We describe the robotic observations that allowed us to measure the total activity of the comet around perihelion, via photometry (dust) and spectroscopy (gas), and compare these results with the measurements at this time by Rosetta's instruments. The peak of activity occurred approximately two weeks after perihelion. The total brightness (dust) largely followed the predictions from Snodgrass et al., with no significant change in total activity levels from previous apparitions. The CN gas production rate matched previous orbits near perihelion, but appeared to be relatively low later in the year.
