- ID:
- ivo://CDS.VizieR/J/ApJ/751/156
- Title:
- Ti and Fe lines in red supergiants
- Short Name:
- J/ApJ/751/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed non-LTE (NLTE) calculations for red supergiant (RSG) stars are presented to investigate the influence of NLTE on the formation of atomic iron and titanium lines in the J band. With their enormous brightness at J band RSG stars are ideal probes of cosmic abundances. Recent LTE studies have found that metallicities accurate to 0.15 dex can be determined from medium-resolution spectroscopy of individual RSGs in galaxies as distant as 10 Mpc. The NLTE results obtained in this investigation support these findings. NLTE abundance corrections for iron are smaller than 0.05 dex for effective temperatures between 3400 K and 4200 K and 0.1 dex at 4400 K. For titanium the NLTE abundance corrections vary smoothly between -0.4 dex and +0.2 dex as a function of effective temperature. For both elements, the corrections also depend on stellar gravity and metallicity. The physical reasons behind the NLTE corrections and the consequences for extragalactic J-band abundance studies are discussed.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/127/2915
- Title:
- Triple systems (cool primary + hot binary)
- Short Name:
- J/AJ/127/2915
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of comparing parameters of evolved cool star plus hot main-sequence star binaries with theoretical isochrones, some discrepancies are found between implied stellar masses and the spectroscopic binary mass function or the measured angular separation. These are naturally explained if there is a third star in the system. Multiplicity is also required to explain some comparisons of "cool plus hot binary" IUE and optical spectral energy distribution analysis with measured flux ratios, especially Tycho's two-color photometry of separate components. Out of a sample of 136 cool-plus-hot binary star systems under study, measurements are now indicating several systems considered double (HD 5373, 23089, 26673, 29094, 49126, 71129, 149379, 179002, 187299), and probably a few others (including HD 136415), to have at least three stellar components. Several other cases of suspected triple systems are confirmed. For comparison, there are eight known triples included in the project. In all, about 25% of the systems contain three or more components within a few arcseconds. Estimated separations are provided, which may be of use when not known from interferometry. In general, the triple systems have one post-main-sequence component and two upper main-sequence components, usually revolving around each other. One new triple system, HD 149379, has as its middle component an F giant in the brief first crossing of the Hertzsprung gap.
- ID:
- ivo://CDS.VizieR/J/A+AS/30/261
- Title:
- UBV and Radial Velocities of SMC Supergiants
- Short Name:
- J/A+AS/30/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From observations at the European Southern Observatory, spectrographic and photometric data are presented for 91 supergiant stars belonging to the Small Magellanic Cloud and its Wing. The data include MK classes for 52 stars, radial velocity data for 51 stars and UBV photometry for 90 stars. In V the limiting magnitude for the spectrographic observations is 13.7 and for the photometric observations 13.9. Whenever possible, radial velocities for interstellar CaII and [OII] have been measured and listed. In Remarks to the Catalogue notes are given for the individual stars concerning the obtained data and comparisons with results of previous investigations.
- ID:
- ivo://CDS.VizieR/J/PAZh/30/855
- Title:
- UBV light curves of IRAS 19200+3457
- Short Name:
- J/PAZh/30/855
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of UBV photometric and spectroscopic observations of the early B supergiant with an IR excess IRAS 19200+3457.
- ID:
- ivo://CDS.VizieR/J/PAZh/35/846
- Title:
- 2000-2008 UBV observations of HD 179821
- Short Name:
- J/PAZh/35/846
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new results of our UBV photometry for HD 179821=V1427 Aql, an F supergiant with an infrared excess, from 2000 to 2008. The semiregular low-amplitude ({Delta}=0.05-0.20mag) photometric variability of the star with a cycle period from 130 to 200 days is caused by pulsations, along with the instability of a variable stellar wind. V1427 Aql also exhibits a long-term trend in the brightness and colors that is probably attributable to a change in the stellar temperature as a result of mass loss episodes, which cause variations in the continuum formation level. We present the results of our JHKLM photometry for V1427 Aql in 1992-2008.
- ID:
- ivo://CDS.VizieR/J/PAZh/26/705
- Title:
- UBV observations of post-AGB supergiants
- Short Name:
- J/PAZh/26/705
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Systematic UBV observations of six variable post-AGB supergiants in 1991-1999 are presented.
- ID:
- ivo://CDS.VizieR/J/PAZh/33/679
- Title:
- UBV phot. and equivalent widths of V886 Her
- Short Name:
- J/PAZh/33/679
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our long-term photometric and spectroscopic observations of a high-latitude B supergiant with an infrared excess - the protoplanetary nebula IRAS 18062+2410. Our UBV observations in 2000-2006 have confirmed the rapid irregular photometric variability of the star with a maximum amplitude as high as 0.4m in V that we found previously. The B-V and U-B color indices vary with amplitudes as high as 0.10m and 0.25m, respectively, and show no clear correlation with the brightness. Our V-band CCD observations on 11 nights in 2006 have revealed brightness trends during the night. The variability of IRAS 18062+2410 is similar in pattern to the light variations in other hot post-AGB objects and some of the nuclei of young planetary nebulae. We assume that pulsations and a variable stellar wind can be responsible for the variability of these stars. In addition to the rapid variability, our 12-year-long observations have revealed a systematic decline in the mean brightness of IRAS 18062+2410.
- ID:
- ivo://CDS.VizieR/J/PAZh/32/48
- Title:
- UBV photometry of HD 331319
- Short Name:
- J/PAZh/32/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of brightness variability in the IR-excess early F supergiant HD 331319, a candidate post-AGB star. Over three years of systematic UBV observations, the star showed low-amplitude (up to 0.17m in V) quasi-periodic brightness variations on a time scale of 45 days. A preliminary analysis of our photometry indicates that HD 331319 and other typical post-AGBF supergiants have a similar pattern of variability. A study of the extinction toward HD 331319 leads us to conclude that the fraction of the circumstellar extinction is small for this star. We present low-resolution spectroscopy for HD 331319 and discuss the spectral classification of post-AGB F supergiants using HD 331319, HD 161796, HD 187885, and HD 56126 as examples.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A47
- Title:
- 8.1um SiO spectra of cool evolved stars
- Short Name:
- J/A+A/561/A47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass-loss mechanism in red giants and red supergiants is not yet understood well. The SiO fundamental lines near 8 m are potentially useful for probing the outer atmosphere, which is essential for clarifying the mass-loss mechanism. However, these lines have been little explored until now. We present high spectral resolution spectroscopic observations of the SiO fundamental lines near 8.1um in 16 bright red giants and red supergiants. Our sample consists of seven normal (i.e., non-Mira) K-M giants (from K1.5 to M6.5), three Mira stars, three optically bright red supergiants, two dusty red supergiants, and the enigmatic object GCIRS3 near the Galactic center.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A167
- Title:
- Using H-bump to identify RSGs in NGC6822
- Short Name:
- J/A+A/647/A167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a case study in which we used a novel method to identify red supergiant (RSG) candidates in NGC 6822 based on their 1.6um H-bump. We collected 32 bands of photometric data for NGC 6822 ranging from the optical to the mid-infrared (MIR), derived from Gaia, PS1, LGGS, VHS, UKIRT, IRSF, HAWK-I, Spitzer, and WISE. Using the theoretical spectra from MARCS, we demonstrate that there is a prominent difference around 1.6um (H-bump) between targets with high and low surface gravity (HSG and LSG). Taking advantage of this feature, we identify efficient color-color diagrams of rzH (r-z versus z-H) and rzK (r-z versus z-K) to separate HSG (mostly foreground dwarfs) and LSG targets (mainly background red giant stars, asymptotic giant branch stars, and RSGs) from crossmatching of optical and near-infrared (NIR) data. Moreover, synthetic photometry from ATLAS9 gives similar results. We further separated RSG candidates from the remaining LSG candidates as determined by the H-bump method by using semi-empirical criteria on NIR color-magnitude diagrams, where both the theoretic cuts and morphology of the RSG population are considered. This separation produced 323 RSG candidates. The simulation of foreground stars with Besancon models also indicates that our selection criteria are largely free from the contamination of Galactic giants. In addition to the H-bump method, we used the traditional BVR method (B-V versus V-R) as a comparison and/or supplement by applying a slightly aggressive cut to select as many RSG candidates as possible (358 targets). Furthermore, the Gaia astrometric solution was used to constrain the sample, where 181 and 193 targets were selected with the H-bump and BVR method, respectively. The percentages of selected targets in the two methods are similar at ~60%, indicating a comparable accuracy of the two methods. In total, there are 234 RSG candidates after combining targets from the two methods, and 140 (~60%) of them are in common. The final RSG candidates are in the expected locations on the mid-infrared color-magnitude diagram with [3.6]-[4.5]<~0 and J-[8.0]~1.0. The spatial distribution is also coincident with the far-ultraviolet-selected star formation regions, suggesting that the selection is reasonable and reliable. We indicate that our method can also be used to identify other LSG targets, such as red giants and asymptotic giant branch stars, and it can also be applied to most of the nearby galaxies by using recent large-scale ground-based surveys. Future ground- and space-based facilities may promote its application beyond the Local Group.
