« Previous |
1 - 10 of 64
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/112/1197
- Title:
- Catalog of cometary emission lines
- Short Name:
- J/AJ/112/1197
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using high-resolution spectra obtained with the Hamilton echelle spectrograph at Lick Observatory, we have constructed a catalog of emission lines observed in comets Swift-Tuttle and Brorsen-Metcalf. The spectra cover the range between 3800A and 9900A with a spectral resolution of {lambda}/{DELTA}{lambda}~42000. In the spectra, we catalog 2997 emission lines of which we identify 2438. We find cometary lines due to H, O, C2, CN, NH2, C3, H2O+, CH, and CH+. We list 559 unidentified lines compiled from the two spectra and comment on possibilities for their origins.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A67
- Title:
- Catalogue of representative meteor spectra
- Short Name:
- J/A+A/580/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present library of meteor spectra in the range 3700-8800{AA} including sporadic meteors, minor showers and major showers in the magnitude range from +2 to -3, corresponding to meteoroid sizes from 1mm to 10mm. Parallel double-station video observations allowed us to compute heliocentric orbits for all meteors. Most observations were performed during the periods of activity of major meteor showers in the years between 2006 and 2012. Spectra are classified according to relative intensities of the low-temperature emission lines of Mg, Na, and Fe.
- ID:
- ivo://CDS.VizieR/J/A+A/566/L5
- Title:
- C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) spectra
- Short Name:
- J/A+A/566/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectral survey in the 1mm wavelength range was undertaken in the long-period comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) using the 30m telescope of the Institut de radioastronomie millimetrique (IRAM) in April and November-December 2013. We report the detection of ethylene glycol (CH_2OH)_2 (aGg' conformer) and formamide (NH_2CHO) in the two comets. The abundances relative to water of ethylene glycol and formamide are 0.2-0.3% and 0.02% in the two comets, similar to the values measured in comet C/1995 O1 (Hale-Bopp). We also report the detection of HCOOH and CH_3_CHO in comet C/2013 R1 (Lovejoy), and a search for other complex species (methyl formate, glycolaldehyde).
- ID:
- ivo://CDS.VizieR/J/A+A/589/A78
- Title:
- C/2012 F6 (Lemmon) and C/2013 R1 spectra (Lovejoy)
- Short Name:
- J/A+A/589/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January - 3 February 2015. We detected 22 molecules and several isotopologues. The H216O and H218O production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of ~25%. The inferred isotope ratios in comet Lovejoy are ^16^O/^18^O=499+/-24 and D/H=1.4+/-0.4*10^-4^ in water, ^32^S/^34^S=24.7+/-3.5 in CS, all compatible with terrestrial values. The ratio ^12^C/^13^C=109+/-14 in HCN is marginally higher than terrestrial and ^14^N/^15^N=145+/-12 in HCN is half the Earth ratio. Several upper limits for D/H or ^12^C/^13^C in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/L2
- Title:
- C/2012 F6 (Lemmon) and C/2012 S1 (ISON) maps
- Short Name:
- J/ApJ/792/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially resolved distributions of HCN, HNC, H_2_CO, and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution ~0.5"), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distributions of molecules and dust in the inner comae of typical bright comets. In both comets, HCN is found to originate from (or within a few hundred kilometers of) the nucleus, with a spatial distribution largely consistent with spherically symmetric, uniform outflow. By contrast, the HNC distributions are clumpy and asymmetrical, with peaks at cometocentric radii ~500-1000km, consistent with release of HNC in collimated outflow(s). Compared to HCN, the H_2_ CO distribution in comet Lemmon is very extended. The interferometric visibility amplitudes are consistent with coma production of H_2_CO and HNC from unidentified precursor material(s) in both comets. Adopting a Haser model, the H_2_CO parent scale length is found to be a few thousand kilometers in Lemmon and only a few hundred kilometers in ISON, consistent with the destruction of the precursor by photolysis or thermal degradation at a rate that scales in proportion to the solar radiation flux.
- ID:
- ivo://CDS.VizieR/J/A+A/564/L2
- Title:
- CH3OH line parameters in comets ISON and Lovejoy
- Short Name:
- J/A+A/564/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present molecular observations carried out with the IRAM 30m telescope at wavelengths around 1.15mm towards the Oort cloud comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy) when they were at 0.6 and 1AU, respectively, from the Sun. We detect HCN, HNC, and CH3OH in both comets, together with the ion HCO+ in comet ISON and a few weak unidentified lines in comet Lovejoy, one of which could be tentatively assigned to methylamine (CH3NH2). The monitoring of the HCN J=3-2 line showed a tenfold enhancement in comet ISON on November 14.4 UT due to an outburst of activity whose exact origin is unknown, although it could be related to some break up of the nucleus. The set of CH_3_OH lines observed was used to derive the kinetic temperature in the coma, 90K in comet ISON and 60K in comet Lovejoy. The HNC/HCN ratios derived, 0.18 in ISON and 0.05 in Lovejoy, are comparable to those found in most previous comets and are consistent with an enhancement of HNC as the comet approaches the Sun. Phosphine (PH3) was also searched for unsuccessfully in both comets through its fundamental 1_0_-0_0_ transition, and 3 sigma upper limits corresponding to PH_3_/H_2_O ratios 4-10 times above the solar P/O elemental ratio could be derived.
- ID:
- ivo://CDS.VizieR/J/A+A/393/1053
- Title:
- 18-cm OH lines in comets
- Short Name:
- J/A+A/393/1053
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since the apparition of comet Kohoutek 1973 XII, the 18-cm lines of the OH radical have been systematically observed in a number of comets with the Nancay radio telescope. Between 1973 and 1999, 52 comets have been successfully detected. This allowed an evaluation of the cometary water production rates and their evolution with time, as well as a study of several physical processes such as the excitation mechanisms of the OH radio lines, the expansion of cometary atmospheres, their anisotropy in relation to non-gravitational forces, and the Zeeman effect in relation to the cometary magnetic field. Part of these observations and their analysis have already been published. The bulk of the results are now organized in a data base. The present paper is a general presentation of the Nancay cometary data base and a more specific description of the observations of 53 cometary apparitions between 1982 and 1999. Comets observed before 1982 are only partly incorporated in the data base. Observations of comets since 2000 have benefited from a major upgrade of the telescope; they will be presented in forthcoming publications.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A3
- Title:
- 6 cold-gas-bearing debris-disc stars spectra
- Short Name:
- J/A+A/614/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial, protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars. This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. The goal of this paper is to investigate the presence of hot gas in the immediate surroundings of the cold-gas-bearing debris-disc central stars. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of beta Pic and Fomalhaut, have been obtained from La Palma (Spain), La Silla (Chile), and La Luz (Mexico) observatories. To verify the presence of hot gas around the sample of stars, we have analysed the CaII H&K and the NaI D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A115
- Title:
- Colors of minor bodies in outer solar system
- Short Name:
- J/A+A/546/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric colours of Minor Bodies in the Outer Solar System (MBOSS). This compilation is based on over 2000 measurement epoch extracted from over 100 articles, and is fairly complete as of Dec. 2011. The average colours and additional information are available in the first file. The second file lists the code of the references used for each object. The third file lists the actual references in bibTex format. The methods used to select the data and compute the averages are described in the accompanying paper. The updated lists are available online at http://www.eso.org/~ohainaut/MBOSS Average photometric colours of Minor Bodies in the Outer Solar System. The table also lists their physico-dynamical class, the number of measurement epochs included in the average, the absolute R-band magnitude R(1,1,{alpha}), and the slope of the spectroscopic gradient (in %/100nm). are presented in table2.dat. For each MBOSS from table2.dat, table3.dat list of the references from which photometric measurements were used. The table also lists the number of measurement epochs included in the average.
