- ID:
- ivo://CDS.VizieR/J/A+A/659/A145
- Title:
- A WISE view on extreme AGB stars
- Short Name:
- J/A+A/659/A145
- Date:
- 18 Mar 2022 08:25:03
- Publisher:
- CDS
- Description:
- Variability is a key property of stars on the asymptotic giant branch (AGB). Their pulsation period is related to the luminosity and mass-loss rate (MLR) of the star. Long-period variables (LPVs) and Mira variables are the most prominent of all types of variability of evolved stars. However, the reddest, most obscured AGB stars are too faint in the optical and have eluded large variability surveys. Our goal is to obtain a sample of LPVs with large MLRs by analysing WISE W1 and W2 light curves (LCs) for about 2000 sources, photometrically selected to include known C-stars with the 11.3 micron silicon carbide dust feature in absorption, and Galactic O-stars with periods longer than 1000 days. Epoch photometry was retrieved from the AllWISE and NEOWISE database and fitted with a sinus curve. Photometry from other variability surveys was also downloaded and fitted. For a subset of 316 of the reddest stars, spectral energy distributions (SEDs) were constructed, and, together with mid-infrared (MIR) spectra when available, fitted with a dust radiative transfer programme in order to derive MLRs. WISE based LCs and fits to the data are presented for all stars. Periods from the literature and periods from refitting other literature data are presented. The results of the spatial correlation with several (IR) databases is presented. About one-third of the sources are found to be not real, but it appears that these cannot be easily filtered out by using WISE flags. Some are clones of extremely bright sources, and in some cases the LCs show the known pulsation period. Inspired by a recent paper, a number of non-variable OH/IRs are identified. Based on a selection on amplitude, a sample of about 750 (candidate) LPVs is selected of which 145 have periods beyond 1000 days, many of them being new. For the subset of the stars with the colours of C-rich extremely red objects (EROs) the fitting of the SEDs (and available MIR spectra) separates them into C- and O-rich objects. Interestingly, the fitting of MIR spectra of mass-losing C-stars is shown to be a powerful tracer of interstellar reddening when AV larger than 2 mag. The number of Galactic EROs appears to be complete up to about 5 kpc and a total dust return rate in the solar neighbourhood for this class is determined. In the LMC 12 additional EROs are identified. Although this represents only about 0.15% of the total known LMC C-star population adding their MLRs increases the previously estimated dust return by 8%. Based on the EROs in the Magellanic Clouds, a bolometric period luminosity is derived. It is pointed out that due to their faintness, EROs and similar O-rich objects are ideal targets for a NIR version of Gaia to obtain distances, observing in the K-band or, even more efficiently, in the L-band.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/IBVS/4459
- Title:
- Baade's variables in Sagitta and Cygnus
- Short Name:
- J/other/IBVS/445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables below show identifications and precise positions for a group of variables found by Walter Baade (1928AN....232...65B) during his Bergedorfer days. The stars reported in this survey are of some historical interest because it was as a result of this work that Baade conceived ideas that led to his later recognition of the two stellar populations among Galactic stars (cf. Osterbrock, 1995, Journ. Hist. Astron., 26, 1).
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/2106
- Title:
- Barium abundance in Galactic Cepheids
- Short Name:
- J/MNRAS/437/2106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an Non-Local Thermodynamic Equilibrium (NLTE) analysis and a homogenous spectral data base, we have determined Ba abundances in a sample of 210 Galactic Cepheids and related objects. We confirm the previous result reported in Andrievsky et al. that the barium distribution in the range of Galactocentric distances from 5 to 18kpc shows very small gradient value. The value determined here - d[Ba/H]/dR~-0.01dex/kpc - is smaller than that for other s-process elements, such as La, Pr, Nd and Sm (Luck & Lambert, 2011AJ....142..136L, Cat. J/AJ/142/136), that typically show gradients of -0.03dex/kpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/3252
- Title:
- Barium abundances in Cepheids
- Short Name:
- J/MNRAS/428/3252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derived the barium atmospheric abundances for a large sample of Cepheids, comprising 270 stars. The sample covers a large range of Galactocentric distances, from about 4 to 15kpc, so it is appropriate to investigate the existence of radial barium abundance gradients in the Galactic disc. In fact, this is the first time that such a comprehensive analysis of the distribution of barium abundances in the Galactic disc has been carried out. As a result, we conclude that the Ba abundance distribution can be characterized by a zero gradient. This result is compared with derived gradients for other elements, and some reasons are briefly discussed for the independence of the barium abundances from Galactocentric distances.
- ID:
- ivo://CDS.VizieR/J/A+A/513/L8
- Title:
- BD+20 1790 radial velocity curve
- Short Name:
- J/A+A/513/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young active star BD +20 1790 has been inferred to host a substellar companion from radial-velocity measurements that detected the reflex motion induced on the parent star. We attempt to completely characterize the radial-velocity signal in order to assess its nature.
- ID:
- ivo://CDS.VizieR/J/AJ/112/2769
- Title:
- Behlen Observatory Survey. IV.
- Short Name:
- J/AJ/112/2769
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Finding charts, accurate coordinates, and light curves are presented for 106 variable stars including 6 which are newly discovered. Parameters descriptive of the light curves are tabulated including periods for 16 stars which lacked them. The periods from the General Catalog of Variable Stars for ten stars were found to be seriously in error. The classification of the stars is discussed. Revisions or refinements of the classifications from the General Catalogue of Variable Stars are suggested for 20 stars and classifications are given for 7 which were previously unclassified. 15%-23% of the Bailey type ab RR Lyrae stars show scatter in their light curves which is suggestive of the Blazhko effect.
- ID:
- ivo://CDS.VizieR/J/AJ/106/2429
- Title:
- Behlen Obs. variables stars survey
- Short Name:
- J/AJ/106/2429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a previous paper, photometry for the first ninety-three stars in a photometric survey of variable stars was discussed. Finding charts, accurate coordinates, and light curves for those stars are presented here. The reliability of the coordinates from the General Catalogue of Variable Stars is discussed. The magnitude scale of the present photometry is compared with that of the Hubble Space Telescope Guide Star Catalogue.
- ID:
- ivo://CDS.VizieR/J/MNRAS/388/444
- Title:
- Berkeley 58 & CG Cas UBV photometry
- Short Name:
- J/MNRAS/388/444
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric, photographic and CCD UBV photometry, spectroscopic observations and star counts are presented for the open cluster Berkeley 58 to examine a possible association with the 4.37d Cepheid CG Cas. The cluster is difficult to separate from the early-type stars belonging to the Perseus spiral arm, in which it is located, but has reasonably well-defined parameters: an evolutionary age of ~10^8^yr, a mean reddening of E(B-V)(B0)=0.70+/-0.03 s.e. and a distance of 3.03+/-0.1kpc (V_0_-M_V_=12.40+/-0.12 s.d.). CG Cas is a likely cluster coronal member on the basis of radial velocity, and its period increase of +0.170+/- 0.01s/y and large light amplitude describe a Cepheid in the third crossing of the instability strip lying slightly blueward of strip centre. Its inferred reddening and luminosity are E(B-V)=0.64+/-0.02 s.e. and <M_V_>=-3.06+/-0.12. A possible K supergiant may also be a cluster member.
- ID:
- ivo://CDS.VizieR/J/ApJ/909/149
- Title:
- Be star omega CMa V light curve & polarimetry
- Short Name:
- J/ApJ/909/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fact that the emission lines seen in the optical spectra of the Be stars originate from a Keplerian circumstellar disk surrounding the central star is gaining more and more observational and theoretical supports. Among all the proposed models explaining the physics of such disks, the Viscous Decretion Disk (VDD) paradigm matches best with the observations. In this work, we challenge the VDD model by applying it to the variety of data of the Be star {omega} CMa observed by different techniques. We find that the VDD model explains the data well, qualitatively. However, we see some quantitative discrepancies that in turn are clues for better understanding the underlying physics of the Be disks. We investigate the possibilities of existing an undetected binary companion, and a radially variable viscous parameter, {alpha} to explain the mismatch between the data and the model.
100. Be stars variability
- ID:
- ivo://CDS.VizieR/J/A+A/335/565
- Title:
- Be stars variability
- Short Name:
- J/A+A/335/565
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high accuracy and the homogeneity of Hipparcos data for bright stars have allowed us to quantify the degree of variability of Be stars. This degree has been found to be highly dependent on the temperature of the star. Rapid variability is the main feature of the 86% of early Be and less than 20% of late Be stars taking into account the limit of detection considered. In addition to Be stars reported in the Hipparcos catalogue (ESA 1997, Cat. <I/239>) as short-period variables, we have been able to enlarge the number of detections as well as to confirm periods previously determined. Be stars that show larger amplitude rapid variations are proposed as candidates for a search of multiperiodicity i.e. as non-radial pulsators. We have also searched for the presence of outbursts and fading events in the Hipparcos data. Outbursts have been frequently and preferentially detected in early Be stars with rather low to moderate v sini while fading events seem to be more conspicuous in stars with higher v sini. Mid-term and long-term variations have also been investigated. Several stars have shown some evidence of temporary quasi-periodic oscillations ranging between 10 and 200 days. Finally information concerning long-term variations is reported. Cycles shorter than or equal to the Hipparcos mission have mainly been detected in stars earlier than B6. Long-term time scales of late Be stars are confirmed to be longer by far.