- ID:
- ivo://CDS.VizieR/J/AJ/125/3037
- Title:
- RI photometry of NGC 205 carbon stars
- Short Name:
- J/AJ/125/3037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a CFH12K survey of the carbon stars in NGC 205 and its surrounding field. We find that the number of C stars in NGC 205 is low (~500) for its luminosity and that very few C stars are seen outside of the 10 isophote, suggesting tidal stripping by M31. Their <M_I_>=-4.54, a magnitude nearly identical to what has been found in other galaxies with numerous C stars. Stars with accurate (R-I) photometry, to I~22.5, are used to determine the outer profile of NGC 205.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/402/801
- Title:
- Runaway carbon stars of Blanco & McCarthy field 37
- Short Name:
- J/A+A/402/801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have been recently faced with the problem of cross-identifying stars recorded in historical catalogues with those extracted from recent fully digitized surveys (such as DENIS and 2MASS). Positions mentioned in the old catalogues are frequently of poor precision, but are generally accompanied by finding charts where the interesting objects are flagged. Those finding charts are sometimes our only link with the accumulated knowledge of past literature. While checking the identification of some of these objects in several catalogues, we had the surprise to discover a number of discrepancies in recent works.The main reason for these discrepancies was generally the blind application of the smallest difference in position as the criterion to identify sources from one historical catalogue to those in more recent surveys. In this paper we give examples of such mis-identifications, and show how we were able to find and correct them.We present modern procedures to discover and solve cross-identification problems, such as loading digitized images of the sky through the Aladin service at CDS, and overlaying entries from historical catalogues and modern surveys. We conclude that the use of good finding charts still remains the ultimate (though time-consuming) tool to ascertain cross-identifications in difficult cases.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/44
- Title:
- RV variability in SDSS dwarf carbon stars
- Short Name:
- J/ApJ/877/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf carbon (dC) stars (main-sequence stars showing carbon molecular bands) were initially thought to be an oxymoron because only asymptotic giant branch (AGB) stars dredge carbon into their atmospheres. Mass transfer from a former AGB companion that has since faded to a white dwarf seems the most likely explanation. Indeed, a few types of giants known to show anomalous abundances- notably, the CH, Ba and CEMP-s stars-are known to have a high binary frequency. The dC stars may be the enhanced-abundance progenitors of most, if not all of these systems, but this requires demonstrating a high binary frequency for dCs. Here, for a sample of 240 dC stars targeted for repeat spectroscopy by the SDSS-IV's Time Domain Spectroscopic Survey, we analyze radial velocity (RV) variability to constrain the binary frequency and orbital properties. A handful of dC systems show large velocity variability (>100km/s). We compare the dCs to a control sample with a similar distribution of magnitude, color, proper motion, and parallax. Using Markov chain Monte Carlo methods, we use the measured {Delta}RV distribution to estimate the binary fraction and the separation distribution assuming both a unimodal and bimodal distribution. We find the dC stars have an enhanced binary fraction of 95%, consistent with them being products of mass transfer. These models result in mean separations of less than 1 au corresponding to periods on the order of 1 yr. Our results support the conclusion that dC stars form from close binary systems via mass transfer.
114. SAGE AGB candidates
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1195
- Title:
- SAGE AGB candidates
- Short Name:
- J/ApJ/723/1195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine variability information from the MAssive Compact Halo Objects survey of the Large Magellanic Cloud with infrared photometry from the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution survey to create a data set of ~30000 variable red sources. We photometrically classify these sources as being on the first ascent of the red giant branch, or as being in one of three stages along the asymptotic giant branch (AGB): oxygen-rich, carbon-rich, or highly reddened with indeterminate chemistry ("extreme" AGB candidates). We present linear period-luminosity (P-L) relationships for these sources using eight separate infrared bands (J, H, Ks, 3.6, 4.5, 5.8, 8.0, and 24um) as proxies for the luminosity. We find that the wavelength dependence of the slope of the P-L relationship is different for different photometrically determined classes of AGB stars. Stars photometrically classified as O-rich show the least variation of slope with wavelength, while dust enshrouded extreme AGB stars show a pronounced trend toward steeper slopes with increasing wavelength. We find that O-rich AGB stars pulsating in the fundamental mode obey a period-magnitude relation with a slope of -3.41+/-0.04 when magnitude is measured in the 3.6um band, in contrast to C-rich AGB stars, which obey a relation of slope -3.77+/-0.05.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/2647
- Title:
- Sgr dSph stars spectral classification
- Short Name:
- J/MNRAS/427/2647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra of 1142 colour-selected stars in the direction of the Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy, of which 1058 were taken with VLT/FLAMES multi-object spectrograph and 84 were taken with the SAAO Radcliffe 1.9-m telescope grating spectrograph. Spectroscopic membership is confirmed (at >99 per cent confidence) for 592 stars on the basis of their radial velocity, and spectral types are given. Very slow rotation is marginally detected around the galaxy's major axis. We identify five S stars and 23 carbon stars, of which all but four carbon stars are newly determined and all but one (PQ Sgr) are likely Sgr dSph members. We examine the onset of carbon richness in this metal-poor galaxy in the context of stellar models. We compare the stellar death rate (one star per 1000-1700yr) with the known planetary nebula dynamical ages and find that the bulk population produce the observed (carbon-rich) planetary nebulae. We compute average lifetimes of S and carbon stars as 60-250 and 130-500kyr, compared to a total thermal-pulsing asymptotic giant branch lifetime of 530-1330kyr. We conclude by discussing the return of carbon-rich material to the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/438/521
- Title:
- SMC C stars B and R light curves
- Short Name:
- J/A+A/438/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC) was selected from the combined 2MASS and DENIS catalogues on the basis of their J-Ks colour. This sample was extended to include confirmed C-stars from the Rebeirot et al. (1993, Cat. <J/A+AS/97/603>) spectroscopic atlas. In this combined sample (N=1149), a smaller number (N=1079) were found to have MACHO observations. For this sub-sample, light curves were determined and 919 stars were found to have high quality light-curves with amplitudes of at least 0.05mag.
- ID:
- ivo://CDS.VizieR/III/132
- Title:
- Southern Galactic Carbon Stars - Near-IR Spectra
- Short Name:
- III/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Over 400 cool carbon stars were found on near-infrared spectrum plates of low-dispersion taken along the southern galactic plane. This represents an approximate 10% increase in the number of such stars known.
- ID:
- ivo://CDS.VizieR/J/ApJS/105/419
- Title:
- Spectral Atlas of Carbon Stars
- Short Name:
- J/ApJS/105/419
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The authors compiled this moderate-resolution spectral atlas to aid in the classification of carbon stars on the Revised MK System (Keenan 1993PASP..105..905K) as refined and extended by the present work. Hence the main purpose of this atlas is to permit rapid and reasonably accurate comparison of the properties of carbon stars in the Solar neighborhood with those in the Galactic bulge, the Magellanic Clouds, and in other nearby external systems. The classification scheme employed makes no assumptions about evolutionary status of the stars but is based entirely on observable criteria. Spectra of 39 stars are presented in detail, along with a catalog of 119 carbon stars classified according to the Revised MK System; the catalog lists also the variability type from Kholopov (1985), and the instrument used. The table is a modified version of table 4 in the source reference. This classification catalog uses not only the stars we observed (the spectral data in this catalog) but also used other material -- photographic plates and some of the stars in the high resolution barnbaum atlas. Stars observed solely with those two instruments are so noted. The spectral files are the data for the standard Carbon Stars in Figs 1 and 2 of the paper.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A62
- Title:
- Spectra of 25 carbon star envelopes
- Short Name:
- J/A+A/628/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to determine the abundances of CS, SiO, and SiS in a large sample of carbon star envelopes covering a wide range of mass loss rates to investigate the potential role that these molecules could play in the formation of dust in the surroundings of the central AGB star. We surveyed a sample of 25 carbon-rich AGB stars in the {lambda}2mm band, more concretely in the J=3-2 line of CS and SiO and in the J=7-6 and J=8-7 lines of SiS, using the IRAM 30m telescope. We performed excitation and radiative transfer calculations based on the LVG method to model the observed lines of the molecules and to derive their fractional abundances in the observed envelopes. We also assessed the effect of infrared pumping in the excitation of the molecules. We detected CS in all 25 targeted envelopes, SiO in 24 of them, and SiS in 17 sources. Remarkably, SiS is not detected in any envelope with a mass loss rate below 10^-6^M_{sun}_/yr while it is detected in all envelopes with mass loss rates above that threshold. We found that CS and SiS have similar abundances in carbon stars envelopes, while SiO is present with a lower abundance. We also found a strong correlation in which the denser the envelope, the less abundant CS and SiO are. The trend is however only tentatively seen for SiS in the high mass loss rate range. Furthermore, we found a relation in which the integrated flux of the MgS dust feature at 30um increases as the fractional abundance of CS decreases. The decline in the fractional abundance of CS with increasing density could be due to gas phase chemistry in the inner envelope or to adsorption onto dust grains. The latter possibility is favored by a correlation between the CS fractional abundance and the 30um feature, which suggests that CS is efficiently incorporated onto MgS dust around C-rich AGB stars. In the case of SiO, the observed abundance depletion with increasing density is most likely caused by an efficient incorporation onto dust grains. The latter possibility is favored by a correlation between the CS fractional abundance and the 30um feature, which suggests that CS is efficiently incorporated onto MgS dust around C-rich AGB stars. In the case of SiO, the observed abundance depletion with increasing density is most likely caused by an efficient incorporation onto dust grains. We conclude that CS and SiO (very likely) and SiS (tentatively) are good candidates to act as gas-phase precursors of dust in C-rich AGB envelopes.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A69
- Title:
- Spectra of 6 SBS stars
- Short Name:
- J/A+A/532/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Faint high latitude carbon stars are rare objects commonly thought to be distant, luminous giants. For this reason they are often used to probe the structure of the Galactic halo; however more accurate investigation of photometric and spectroscopic surveys has revealed an increasing percentage of nearby objects with luminosities of main sequence stars. We analyzed new optical spectra and photometry and used astronomical databases available on the web, aiming at clarifying the nature of the ten carbon star candidates present in the General Catalogue of the Second Byurakan Survey. We verified that two stars are N-type giants already confirmed by other surveys. We found that four candidates are M-type stars and confirmed the carbon nature of the remaining four stars; the characteristics of three of them are consistent with an early CH giant type. The fourth candidate, SBS 1310+561 identified with a high proper motion star, is a rare type of dwarf carbon showing emission lines in its optical spectrum. We estimated absolute magnitudes and distances to the dwarf carbon and the CH stars. Our limited sample confirmed the increasing evidence that spectroscopy or colour alone are not conclusive luminosity discriminants for CH-type carbon stars.
