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- ID:
- ivo://CDS.VizieR/J/A+A/417/479
- Title:
- RI photometry of NGC 185 carbon stars
- Short Name:
- J/A+A/417/479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the CFH12K wide field camera to survey the carbon star population of NGC 185 using the CN-TiO technique. 145 C stars are identified with a mean <I>=19.99+/-0.05, corresponding to <M_I_>=-4.41+/-0.05, a mean luminosity similar to what was recently found for the C star population of NGC 147. The stellar surface density profile of NGC 185 follows a power law with an exponential scale length of 2.53+/-0.07'. The surface density of C stars follows also a power law but with a smaller scale length, 1.56+/-0.06, demonstrating that the intermediate-age population of NGC 185 is more concentrated than its old population. A tidal radius, r_t_=22.5+/-2.2' is determined from red giant star counts. The C/M ratio of NGC 185 is 0.17+/-0.02 with no apparent sign of a radial gradient. We compare the carbon star populations of NGC 185 and NGC 147 to conclude that it is unlikely that they form a close pair.
- 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.
- 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.
136. 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/J/A+A/633/A135
- Title:
- Solar neighbourhood carbon stars properties
- Short Name:
- J/A+A/633/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars evolving along the Asymptotic Giant Branch can become carbon-rich in the final part of their evolution. The detailed description of their spectra has led to the definition of several spectral types, namely: N, SC, J and R types. Up to now, differences among them have been partially established only on the basis of their chemical properties. An accurate determination of the luminosity function (LF) and kinematics together with their chemical properties is extremely important for testing the reliability of theoretical models and establishing on a solid basis the stellar population membership of the different carbon star types. Using Gaia Data Release 2 (Gaia DR2) astrometry, we determine the LF and kinematic properties of a sample of 210 carbon stars with different spectral types in the Solar neighbourhood, including some R-hot stars, with measured parallaxes better than 20%. Their spatial distribution and velocity components are also derived. Furthermore, the use of the infrared Wesenheit function allows us to identify the different spectral types in a Gaia-2MASS diagram. We find that the combined LF of N- and SC-type stars are consistent with a Gaussian distribution peaking at M_bol_~-5.2mag. The resulting LF however shows two tails at lower and higher luminosities more extended than those previously found, indicating that AGB carbon stars with Solar metallicity may reach M_bol_~-6.0mag. This contrasts with the narrower LF derived in Galactic carbon Miras from previous studies.We find that J-type stars are about half a magnitude fainter on average than N- and SC-type stars, while R-hot stars are half a magnitude brighter than previously found although, in any case, fainter by several magnitudes than the rest of carbon types. Part of these differences are due to systematically lower parallaxes measured by Gaia DR2 with respect to Hipparcos ones, in particular for sources with parallax Plx<1mas. The Galactic spatial distribution and velocity components of the N-, SC- and J-type stars are very similar, while about 30% of the R-hot stars in the sample are located at distances larger than ~ 500 pc from the Galactic Plane, and show a significant drift with respect to the local standard of rest. The LF derived for N- and SC-type in the Solar neighbourhood fully agrees with the expected luminosity of stars of 1.5-3M _{sun}_ on the AGB. On a theoretical basis, the existence of an extended low luminosity tail would require a contribution of extrinsic low mass carbon stars, while the high luminosity one would imply that stars with mass up to ~5M _{sun}_ may become carbon stars on the AGB. J-type stars not only differ significantly in their chemical composition with respect to the N- and SC-types but also in their LF, which reinforces the idea that these carbon stars belong to a different type whose origin is still unknown. The derived luminosities of R-hot stars make these stars unlikely to be in the red-clump as previously claimed. On the other hand, the derived spatial distribution and kinematic properties, together with their metallicity, indicate that most of the N-, SC- and J-type stars belong to the thin disc population, while a significant fraction of R-hot stars show characteristics compatible with the thick disc.
- 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.
