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- ID:
- ivo://China-VO/CAsDC
- Title:
- Chinese Astronomical Data Center
- Short Name:
- CAsDC
- Date:
- 29 Apr 2018
- Publisher:
- Chinese Virtual Observatory
- Description:
- Chinese Astronomical Data Center
- ID:
- ivo://CDS.VizieR/J/PASP/122/347
- Title:
- Chinese Small Telescope ARray (CSTAR)
- Short Name:
- J/PASP/122/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2008 January the twenty-fourth Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g,r,i, and open) and has a 4.5{deg}x4.5{deg} field of view (FOV). It operates robotically as part of the Plateau Observatory, PLATO, with each telescope taking an image every ~30s throughout the year whenever it is dark. During 2008, CSTAR 1 performed almost flawlessly, acquiring more than 0.3 million -band images for a total integration time of 1728hr during 158 days of observations. For each image taken under good sky conditions, more than 10,000 sources down to magnitude could be detected. We performed aperture photometry on all the sources in the field to create the catalog described herein. Since CSTAR has a fixed pointing centered on the south celestial pole (Dec=-90{deg}), all the sources within the FOV of CSTAR were monitored continuously for several months. The photometric catalog can be used for studying any variability in these sources, and for the discovery of transient sources such as supernovae, gamma-ray bursts, and minor planets.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A198
- Title:
- CHIPS II. O stars in Trumpler 14 CHIPS-Tr14
- Short Name:
- J/A+A/658/A198
- Date:
- 25 Feb 2022 07:07:49
- Publisher:
- CDS
- Description:
- Most massive stars belong to multiple systems, yet the formation process leading to such high multiplicity remain insufficiently understood. To help constrain the different formation scenarios that exist, insights on the low-mass end of the companion mass function of such stars is crucial. However, this is a challenging endeavour as (sub-)solar mass companions at angular separations {rho} below 1" (corresponding to 1000-3000au in nearby young open clusters and OB associations) are difficult to detect due to the large brightness contrast with the central star. With the Carina High-contrast Imaging Project of massive Stars (CHIPS), we aim to obtain statistically significant constraints on the presence and properties of low-mass companions around massive stars at a previously unreachable observing window ({Delta}mag>=10 at {rho}<= 1"). In this second paper in the series, we focus on the Trumpler 14 cluster, which harbours some of the youngest and most massive O-type stars in the Milky Way. We obtained VLT-SPHERE observations of seven O-type objects in Trumpler 14 using the IRDIFS_EXT mode. These allow us to search for companions at separations larger than 0.15" (~360au) and down to magnitude contrast >10 mag in the near-infrared. We used angular and spectral differential imaging along with PSF fitting to detect sources and measure their flux relative to that of the central object. We detected 211 sources with near-infrared magnitude contrast in the range of 2 to 12. The closest companion, at only 0.26", is characterised as a 1.4M_{sun}_ stars with an age of 0.6Myr, in excellent agreement with previous age estimates for Tr14. The mass function peaks at about 0.4M_{sun}_ and presents a dearth of stars in the 0.5 to 0.8M_{sun}_ mass range compared to previous estimates of the initial mass function in Tr14.
3705. Chiron occultations
- ID:
- ivo://CDS.VizieR/J/AJ/107/1814
- Title:
- Chiron occultations
- Short Name:
- J/AJ/107/1814
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A photographic search was conducted for stars that may be occulted by the unusual solar system object (2060) Chiron during the period from fall 1993 through summer 1996. 44 candidates were identified to a limiting V magnitude of 16, and for which the minimum appulse separation with Chiron is predicted to be less than 2.5arcsec. The successful observation of a stellar occultation by Chiron would give a direct measure of its diameter (currently estimated to be between 60 and 300km), and would help considerably in constraining Chiron's surface properties and volatile makeup. If at the time of the occultation, Chiron exhibits a significant coma, there is also the potential for measuring the optical-depth profile of the dust in its inner coma.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/L5
- Title:
- CH_3_NCO (methyl isocyanate) transition frequencies
- Short Name:
- J/ApJ/812/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new interstellar molecule, CH_3_NCO (methyl isocyanate), has been detected using the 12m telescope of the Arizona Radio Observatory (ARO). CH_3_NCO was identified in spectra covering 48GHz (68-116GHz) in the 3mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (K_a_=0 and K_a_=1 only; E_u_<60K) originating in five consecutive transitions (J=8->7, 9->8, 10->9, 11->10, and 12->11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with T_R_^*^~20-70mK. The CH_3_NCO spectra also appear to exhibit two velocity components near V_LSR_~62 and 73km/s, both with {Delta}V_1/2_~10km/s --typical of molecules such as CH_2_CHCN, HNCO, and HCOOCH_3_ in Sgr B2(N). The column density of CH_3_NCO in Sgr B2(N) was determined to be N_tot_~2.3x10^13^ and 1.5x10^13^/cm^2^ for the 62 and 73km/s components, corresponding to fractional abundances, relative to H_2_, of f~7.6x10^-12^ and 5.0x10^-12^, respectively. CH_3_NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ~1.3% of water; in Sgr B2(N), CH_3_NCO is roughly ~0.04% of the H_2_O abundance.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A19
- Title:
- CH_2_NH accurate rotational rest frequencies
- Short Name:
- J/A+A/544/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methanimine (CH_2_NH) has been detected in different astronomical sources, both galactic (as in several "hot cores", the circumstellar enevolope IRC+10216, and the L183 pre-stellar core) and extragalactic, and is considered a pre-biotic interstellar molecule. Its ground-state rotational spectrum has been studied in the laboratory up to 172GHz, well below the spectral ranges covered by Herschel/HIFI and the ALMA bands 9 and 10. In this laboratory study, we extend into the submillimetre-wave region the detection of the rotational spectrum of CH_2_NH in its vibrational ground state.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A49
- Title:
- CH_3_NHCHO rotational spectroscopy
- Short Name:
- J/A+A/601/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- N-methylformamide, CH_3_NHCHO, may be an important molecule for interstellar pre-biotic chemistry because it contains a peptide bond, which in terrestrial chemistry is responsible for linking amino acids in proteins. The rotational spectrum of the most stable trans conformer of N-methylformamide is complicated by strong torsion-rotation interaction due to the low barrier of the methyl torsion. For this reason, the theoretical description of the rotational spectrum of the trans conformer has up to now not been accurate enough to provide a firm basis for its interstellar detection. In this context, as a prerequisite for a successful interstellar detection, our goal is to improve the characterization of the rotational spectrum of N-methylformamide. We use two absorption spectrometers in Kharkiv and Lille to measure the rotational spectra over the frequency range 45-630 GHz. The analysis is carried out using the Rho-axis method and the RAM36 code. We search for N-methylformamide toward the hot molecular core Sagittarius (Sgr) B2(N2) using a spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). The astronomical spectra are analyzed under the assumption of local thermodynamic equilibrium. The astronomical results are put into a broader astrochemical context with the help of a gas-grain chemical kinetics model. The new laboratory data set for the trans conformer of N-methylformamide consists of 9469 distinct line frequencies with J<=62, including the first assignment of the rotational spectra of the first and second excited torsional states. All these lines are fitted within experimental accuracy for the first time. Based on the reliable frequency predictions obtained in this study, we report the tentative detection of N-methylformamide towards Sgr B2(N2). We find N-methylformamide to be more than one order of magnitude less abundant than formamide (NH_2_CHO), a factor of two less abundant than the unsaturated molecule methyl isocyanate (CH_3_NCO), but only slightly less abundant than acetamide (CH_3_CONH_2_). We also report the tentative detection of the 15N isotopologue of formamide (^15^NH_2_CHO) toward Sgr B2(N2). The chemical models indicate that the efficient formation of HNCO via NH + CO on grains is a necessary step in the achievement of the observed gas-phase abundance of CH_3_NCO. Production of CH_3_NHCHO may plausibly occur on grains either through the direct addition of functional-group radicals or through the hydrogenation of CH_3_NCO. Conclusions. Provided the detection of N-methylformamide is confirmed, the only slight underabundance of this molecule compared to its more stable structural isomer acetamide and the sensitivity of the model abundances to the chemical kinetics parameters suggest that the formation of these two molecules is controlled by kinetics rather than thermal equilibrium.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A120
- Title:
- CH_3_OCHD_2_ experimental frequencies
- Short Name:
- J/A+A/651/A120
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In 2013, we have published the first rotational analysis and detection of mono-deuterated dimethyl ether in the solar-type protostar IRAS 16293-2422 with the IRAM 30m telescope. Dimethyl ether is one of the most abundant complex organic molecules (COMs) in star-forming regions and their D-to-H (D/H) ratios is important to understand its chemistry and trace the source history. We present the first analysis of doubly-deuterated dimethyl ether (methoxy-d2-methane, 1,1-dideuteromethylether) in its ground- vibrational state, based on an effective Hamiltonian for an asymmetric rotor molecules with internal rotors. The analysis covers the frequency range 0.15-1.5THz. The laboratory rotational spectrum of this species was measured between 150 and 1500GHz with the Lille's submillimeter spectrometer. For the astronomical detection, we used the Atacama Large Millimeter/submillimeter Array (ALMA) observations from the Protostellar Interferometric Line Survey, PILS. New sets of spectroscopic parameters have been determined by a least squares fit with the ERHAM code for both symmetric and asymmetric conformers. As for the mono-deuterated species, these parameters have permitted the first identification in space of both conformers of a doubly-deuterated dimethyl ether via detection near the B component of the Class 0 protostar IRAS 16293-2422.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/L46
- Title:
- CH_3_OCH_2_OH ALMA detection in NGC 6334I
- Short Name:
- J/ApJ/851/L46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of interstellar methoxymethanol (CH_3_OCH_2_OH) in Atacama Large Millimeter/submillimeter Array (ALMA) Bands 6 and 7 toward the MM1 core in the high-mass star-forming region NGC 6334I at ~0.1-1" spatial resolution. A column density of 4(2)x10^18^cm^-2^ at T_ex_=200K is derived toward MM1, ~34 times less abundant than methanol (CH_3_OH), and significantly higher than predicted by astrochemical models. Probable formation and destruction pathways are discussed, primarily through the reaction of the CH_3_OH photodissociation products, the methoxy (CH_3_O) and hydroxymethyl (CH_2_OH) radicals. Finally, we comment on the implications of these mechanisms on gas-phase versus grain-surface routes operative in the region, and the possibility of electron-induced dissociation of CH3OH rather than photodissociation.
