- ID:
- ivo://CDS.VizieR/J/ApJ/801/69
- Title:
- Iron EWs for 21 giant star members of NGC3201
- Short Name:
- J/ApJ/801/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 3201 is a globular cluster suspected to have an intrinsic spread in the iron content. We re-analyzed a sample of 21 cluster stars observed with UVES-FLAMES at the Very Large Telescope and for which Simmerer et al. (2013ApJ...764L...7S) found a 0.4dex wide [Fe/H] distribution with a metal-poor tail. We confirmed that when spectroscopic gravities are adopted, the derived [Fe/H] distribution spans ~0.4dex. On the other hand, when photometric gravities are used, the metallicity distribution from Fe I lines remains large, while that derived from Fe II lines is narrow and compatible with no iron spread. We demonstrate that the metal-poor component claimed by Simmerer et al. (2013ApJ...764L...7S) is composed by asymptotic giant branch stars that could be affected by non-local thermodynamical equilibrium effects driven by iron overionization. This leads to a decrease of the Fe I abundance, while leaving the Fe II abundance unaltered. A similar finding has been already found in asymptotic giant branch stars of the globular clusters M5 and 47 Tucanae. We conclude that NGC 3201 is a normal cluster, with no evidence of intrinsic iron spread.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/440/631
- Title:
- IR photometry of LMC O-rich evolved stars
- Short Name:
- J/MNRAS/440/631
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars, we have computed a grid of MODUST radiative-transfer models for a range of dust compositions, mass-loss rates, dust-shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5-35{mu}m Spitzer infrared spectrograph (IRS) spectra and broad-band photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range ~8x10^-8^-5x10^-6^M_{sun}_/yr, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron, provides a good fit to the observed spectra. Furthermore, we show from dust models that the AKARI [11]-[15] versus [3.2]-[7] colour-colour diagram is able to determine the fractional abundance of alumina in O-rich AGB stars.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1003
- Title:
- IR photometry of massive LMC stars
- Short Name:
- J/AJ/138/1003
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 1750 massive stars in the Large Magellanic Cloud (LMC), with accurate spectral types compiled from the literature, and a photometric catalog for a subset of 1268 of these stars, with the goal of exploring their infrared properties. The photometric catalog consists of stars with infrared counterparts in the Spitzer SAGE survey database, for which we present uniform photometry from 0.3 to 24um in the UBVIJHKs+IRAC+MIPS24 bands. The resulting infrared color-magnitude diagrams illustrate that the supergiant B[e], red supergiant, and luminous blue variable (LBV) stars are among the brightest infrared point sources in the LMC, due to their intrinsic brightness, and at longer wavelengths, due to dust. We detect infrared excesses due to free-free emission among ~900 OB stars, which correlate with luminosity class. We confirm the presence of dust around 10 supergiant B[e] stars, finding the shape of their spectral energy distributions (SEDs) to be very similar, in contrast to the variety of SED shapes among the spectrally variable LBVs. The similar luminosities of B[e] supergiants (log L/L_{sun}_>=4) and the rare, dusty progenitors of the new class of optical transients (e.g., SN 2008S and NGC 300 OT), plus the fact that dust is present in both types of objects, suggests a common origin for them. We find the infrared colors for Wolf-Rayet stars to be independent of spectral type and their SEDs to be flatter than what models predict.
- ID:
- ivo://CDS.VizieR/J/AJ/140/416
- Title:
- IR photometry of massive stars in the SMC
- Short Name:
- J/AJ/140/416
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 5324 massive stars in the Small Magellanic Cloud (SMC), with accurate spectral types compiled from the literature, and a photometric catalog for a subset of 3654 of these stars, with the goal of exploring their infrared properties. The photometric catalog consists of stars with infrared counterparts in the Spitzer SAGE-SMC survey database, for which we present uniform photometry from 0.3 to 24um in the UBVIJHKs+IRAC+MIPS24 bands.
- ID:
- ivo://CDS.VizieR/J/AJ/162/187
- Title:
- IRTF spectral indices for giant stars
- Short Name:
- J/AJ/162/187
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We present infrared spectral indices (1.0-2.3{mu}m) of Galactic late-type giants and red supergiants (RSGs). We used existing and new spectra obtained at resolution power R=2000 with SpeX on the IRTF telescope. While a large CO equivalent width (EW), at 2.29{mu}m ([CO,2.29]>~45{AA}) is a typical signature of RSGs later than spectral type M0, [CO] of K-type RSGs and giants are similar. In the [CO,2.29] versus [MgI,1.71] diagram, RSGs of all spectral types can be distinguished from red giants because the MgI line weakens with increasing temperature and decreasing gravity. We find several lines that vary with luminosity, but not temperature: SiI (1.59{mu}m), Sr (1.033{mu}m), Fe+Cr+Si+CN (1.16{mu}m), Fe+Ti (1.185{mu}m), Fe+Ti (1.196{mu}m), Ti+Ca (1.28{mu}m), and Mn (1.29{mu}m). Good markers of CN enhancement are the Fe+Si+CN line at 1.087{mu}m and CN line at 1.093{mu}m. Using these lines, at the resolution of SpeX, it is possible to separate RSGs and giants. Contaminant O-rich Mira and S-type AGBs are recognized by strong molecular features due to water vapor features, TiO band heads, and/or ZrO absorption. Among the 42 candidate RSGs that we observed, all but one were found to be late types. Twenty-one have EWs consistent with those of RSGs, 16 with those of O-rich Mira AGBs, and one with an S-type AGB. These infrared results open new, unexplored, potential for searches at low resolution of RSGs in the highly obscured innermost regions of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/464
- Title:
- JHK lightcurves of red giants in the SMC
- Short Name:
- J/MNRAS/448/464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long-term JHK light curves have recently become available for large numbers of the more luminous stars in the Small Magellanic Cloud (SMC). We have used these JHK light curves, along with OGLE (Optical Gravitational Lensing Experiment) V and I light curves, to examine the variability of a sample of luminous red giants in the SMC which show prominent long secondary periods (LSPs). The origin of the LSPs is currently unknown. In oxygen-rich stars, we found that while most broad-band colours (e.g. V- I) get redder when an oxygen-rich star dims during its LSP cycle, the J-K colour barely changes and sometimes becomes bluer. We interpret the J-K colour changes as being due to increasing water vapour absorption during declining light caused by the development of a layer of dense cool gas above the photosphere. This result and previous observations which indicate the development of a chromosphere between minimum to maximum light suggest that the LSP phenomenon is associated with the ejection of matter from the stellar photosphere near the beginning of light decline. We explore the possibility that broad-band light variations from the optical to the near-infrared regions can be explained by either dust absorption by ejected matter or large spots on a rotating stellar surface. However, neither model is capable of explaining the observed light variations in a variety of colour-magnitude diagrams. We conclude that some other mechanism is responsible for the light variations associated with LSPs in red giants.
- ID:
- ivo://CDS.VizieR/J/A+A/375/527
- Title:
- JHKL' photometry of AGB stars
- Short Name:
- J/A+A/375/527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multi-epoch near-infrared photometry for a sample of long period variables (SR, L, Mira). Data have been obtained at the Observatorio del Teide using the 1.5m "Carlos Sanchez Telescope" with the "CVF Photometer-Spectrophotometer". The sample has been selected based on three observing programs at the ISO satellite.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/209
- Title:
- JHK(L') photometry of giant stars
- Short Name:
- J/A+AS/131/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a three-year campaign of broad-band photometry in the near-infrared J, H, K and L' bands for a sample of approximately 250 giant stars carried out at the Observatorio del Teide (Tenerife, Spain). Transformations of the Telescopio Carlos Sanchez system into/from several currently used infrared systems are extended to the redward part of the colour axis. The linearity of our photometric system in the range -3mag<K<10.5mag is inferred from the intercomparison of data of stars common to this and other photometric systems. A preliminary assessment of the photometric extinction profile of the Observatorio del Teide in JHKL' is also provided. These observations are a continuation of a programme aimed towards the progressive completion of a whole grid of T_eff_-[Fe/H]-log(g)-colour relations for population I and II stars. The analysis of optical and IR colour-colour diagrams reveals that the range F0III-K5III is well sampled for 0.5>[Fe/H]>-3. Data of comparable quality previously published have been added to the sample in order to increase the reliability of the relations to be obtained. We also provide mean IR colours for giant stars according to spectral type.
- ID:
- ivo://CDS.VizieR/J/A+A/458/533
- Title:
- JHKL' photometry of selected AGB stars
- Short Name:
- J/A+A/458/533
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a near-infrared monitoring programme of a selected sample of stars, initially suspected to be Mira variables and OH/IR stars, covering more than a decade of observations. The objects monitored cover the typical range of IRAS colours shown by O-rich stars on the asymptotic giant branch and show a surprisingly large diversity of variability properties. Sixteen objects are confirmed as large-amplitude variables.
- ID:
- ivo://CDS.VizieR/J/A+A/445/69
- Title:
- JHK' photometry of C stars in NGC 147
- Short Name:
- J/A+A/445/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared J, H and K' images were used to investigate the stellar contents of the asymptotic giant branch (AGB) population in the nearby dwarf elliptical galaxy NGC 147. The obtained (K,J-K) and (K,H-K) color-magnitude diagrams contain stars of AGB and red giant branch populations, where the former consists of a group of bright blue stars, a dominant population of M giant and a red C star population.We identified 91 AGB C stars in NGC 147 with the mean absolute magnitude and colors of <M_K_>=-7.56, <(J-K)_0_>=1.81 and <(H-K)_0_>=0.74. The estimated number ratio of C stars to M giant stars (C/M) is 0.16+/-0.02. The estimated local C/M ratios of 0.14+/-0.02 for the inner region (r<70") and 0.19+/-0.03 for the outer region (r>70") indicate a weak radial gradient. The mean bolometric magnitude of 91 C stars in NGC 147 is <M_bol_>=-4.32+/-0.49. The bolometric luminosity function of M giant stars in NGC 147 extends up to M_bol_=-5.8 magnitude, and that of only C stars spans -5.6<M_bol_<-3.5. The color histograms of AGB stars in (J-K) and (H-K) show a main peak containing M giant stars, a red tail containing C stars with a weak excess, and a blue excess possibly due to bright blue foreground stars and AGB stars younger than M giants. The comparison of the theoretical isochrone models with the color distribution and the brightness of AGB stars indicates that most of the bright M giants in NGC 147 were formed at log(t_yr_)~8.4 with a range of 8.2~8.6. Ages of the majority of M giant stars in NGC 147 are similar to those of younger M giant stars in its companion NGC 185, while their formation occurred more recently than the older M giant stars in NGC 185 by ~2Gyrs.
