- ID:
- ivo://CDS.VizieR/J/A+A/488/675
- Title:
- Infrared photometry of mass-losing AGB stars
- Short Name:
- J/A+A/488/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asymptotic giant branch (AGB) phases mark the end of the evolution for low- and intermediate-mass stars. Our understanding of the mechanisms through which they eject the envelope and our assessment of their contribution to the mass return to the interstellar medium and to the chemical evolution of Galaxies are hampered by poor knowledge of their luminosities and mass loss rates, both for C-rich and for O-rich sources. We plan to establish criteria permitting a more quantitative determination of luminosities (and subsequently of mass loss rates) for the various types of AGB stars on the basis of infrared fluxes. In this paper, in particular, we concentrate on O-rich and s-element-rich MS, S stars and include a small sample of SC stars. We reanalyze the absolute bolometric magnitudes and colors of MS, S, SC stars on the basis of a sample of intrinsic (single) and extrinsic (binary) long period variables. We derive bolometric corrections as a function of near- and mid-infrared colors, adopting as references a group of stars for which the spectral energy distribution could be reconstructed in detail over a large wavelength range. We determine the absolute HR diagrams, and compare luminosities and colors of S-type giants with those, previously derived, of C-rich AGB stars. Luminosity estimates are also verified on the basis of existing period-luminosity relations valid for O-rich Miras. S star bolometric luminosities are almost indistinguishable from those of C-rich AGB stars. On the contrary, their circumstellar envelopes are thinner and less opaque. Despite this last property the IR wavelengths remain dominant, with the bluest stars having their maximum emission in the H or K(short) bands. Near-to-mid infrared color differences are in any case smaller than for C stars. Based on period-luminosity relations for O-rich Miras and on Magnitude-color relations for the same variables we show how approximate distances (hence intrinsic parameters) for sources of so far unknown parallax can be inferred. We argue that most of the sources have a rather small mass (<2M_{sun}_); dredge-up might then be not effective enough to let the C/O ratio exceed unity.
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- ID:
- ivo://CDS.VizieR/J/AJ/153/35
- Title:
- Infrared spectroscopy of symbiotic stars. XI.
- Short Name:
- J/AJ/153/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Employing new infrared radial velocities, we have computed spectroscopic orbits of the cool giants in four southern S-type symbiotic systems. The orbits for two of the systems, Hen 3-461 and Hen 3-828, have been determined for the first time, while orbits of the other two, SY Mus and AR Pav, have previously been determined. For the latter two systems, we compare our results with those in the literature. The low mass of the secondary of SY Mus suggests that it has gone through a common envelope phase. Hen 3-461 has an orbital period of 2271 days, one of the longest currently known for S-type symbiotic systems. That period is very different from the orbital period proposed previously from its photometric variations. The other three binaries have periods between 600 and 700 day, values that are typical for S-type symbiotic orbits. Basic properties of the M giant components and the distance to each system are determined.
- ID:
- ivo://CDS.VizieR/J/ApJ/456/174
- Title:
- Intermediate-Mass Population in NGC 604
- Short Name:
- J/ApJ/456/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry of stars in the giant H II region NGC 604 in M33. The photometry is measured from Hubble Space Telescope images through the F336W, F555W, and F814W broadband filters. Color- magnitude diagrams of the stars in NGC 604 show a main sequence detected down to an M_F555W,0 of -1 (nearly 6M_{sun}_). In addition, there are luminous stars that are probably blue and red supergiants. Based on the previously known presence of Wolf-Rayet stars, we take the age of the cluster to be 3-5Myr. We measure an initial mass function for intermediate-mass stars (6.5-18M_{sun}_) that has a slope of -1.6+/-0.7. This slope is, within the uncertainties, similar to those found for OB associations in the Milky Way and Magellanic Clouds. The density of the luminous stars in NGC 604 is also comparable to that of OB associations in those galaxies even though the total number of stars is greater in NGC 604. A few subclamps have densities that are higher by as much as a factor of 10. A comparison with R136 in the LMC emphasizes that the formation of a large number of massive stars does not necessarily entail a high concentration of those stars.
- ID:
- ivo://CDS.VizieR/J/A+A/349/L69
- Title:
- Interstellar extinction
- Short Name:
- J/A+A/349/L69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DENIS observations in the J(1.25{mu}m) and K_S_(2.15{mu}m) bands together with isochrones calculated for the RGB and AGB phase are used to draw an extinction map of the inner Galactic Bulge. The uncertainty in this method is mainly limited by the optical depth of the Bulge itself. A comparison with fields of known extinction shows a very good agreement. We present an extinction map for the inner Galactic Bulge (~20{deg}^2^)
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/679
- Title:
- IRAS 22023+5249 spectroscopy
- Short Name:
- J/MNRAS/421/679
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first high-resolution (R~50000) optical spectrum of the B-type star, LS III +52 24, identified as the optical counterpart of the hot post-asymptotic giant branch (post-AGB) candidate IRAS 22023+5249 (I22023) is presented. We report the detailed identifications of the observed absorption and emission features in the full wavelength range (4290-9015{AA}) as well as the atmospheric parameters and photospheric abundances (under the local thermodynamic equilibrium approximation) for the first time. The nebular parameters (Te, Ne) are also derived.
- ID:
- ivo://CDS.VizieR/J/ApJ/834/185
- Title:
- IR-bright MSX sources in the SMC with Spitzer/IRS
- Short Name:
- J/ApJ/834/185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Infrared Spectrograph (IRS) on the Spitzer Space Telescope to observe stars in the Small Magellanic Cloud (SMC) selected from the Point Source Catalog of the Midcourse Space Experiment (MSX). We concentrate on the dust properties of the oxygen-rich evolved stars. The dust composition has smaller contributions from alumina compared to the Galaxy. This difference may arise from the lower metallicity in the SMC, but it could be a selection effect, as the SMC sample includes more stars that are brighter and thus more massive. The distribution of the SMC stars along the silicate sequence looks more like the Galactic sample of red supergiants than asymptotic giant branch stars (AGBs). While many of the SMC stars are definitively on the AGB, several also show evidence of hot bottom burning. Three of the supergiants show PAH emission at 11.3{mu}m. Two other sources show mixed chemistry, with both carbon-rich and oxygen-rich spectral features. One, MSX SMC 134, may be the first confirmed silicate/carbon star in the SMC. The other, MSX SMC 049, is a candidate post-AGB star. MSX SMC 145, previously considered a candidate OH/IR star, is actually an AGB star with a background galaxy at z=0.16 along the same line of sight. We consider the overall characteristics of all the MSX sources, the most infrared-bright objects in the SMC, in light of the higher sensitivity and resolution of Spitzer, and compare them with the object types expected from the original selection criteria. This population represents what will be seen in more distant galaxies by the upcoming James Webb Space Telescope (JWST). Color-color diagrams generated from the IRS spectra and the mid-infrared filters on JWST show how one can separate evolved stars from young stellar objects (YSOs) and distinguish among different classes of YSOs.
- ID:
- ivo://CDS.VizieR/J/A+A/448/181
- Title:
- IR colours of AGB and post-AGB stars
- Short Name:
- J/A+A/448/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the advent of space missions, like SPITZER and ASTRO-F, with sensitive detectors in the near- and mid-infrared covering a reasonable field-of-view and having a good spatial resolution it will be possible to detect individual AGB stars in Local Group galaxies. The filters used by these missions are non-standard and different from mission to mission. In this paper the colours of mass-losing AGB and post-AGB stars are calculated in the broad-band filters of the SPITZER and ASTRO-F missions, as well as Bessell V,I and 2MASS J,H,K to connect these results to existing ground-based data. The models are calculated for carbon- and oxygen-rich chemistry and cover different effective temperatures and dust compositions.
- ID:
- ivo://CDS.VizieR/J/A+A/330/676
- Title:
- IRC+10216 Silicon and sulfur chemistry
- Short Name:
- J/A+A/330/676
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a dynamical and chemical model of the inner wind of the carbon-rich, AGB star IRC+10216. We include the effect of pulsation-driven shocks on the gas envelope close to the stellar photosphere and construct an extended chemical model that includes in particular the chemistry of hydrocarbon species and silicon and sulphur-bearing molecules. The derived theoretical abundances for many molecules are in excellent agreement with values obtained from observations of infrared ro-vibrational molecular lines. We confirm the ``parent'' character of certain chemical species and show that the inner wind of IRC+10216, and more generally of evolved AGB stars, is an active dynamical and chemical region where molecules are formed and processed.
- ID:
- ivo://CDS.VizieR/J/PASP/124/519
- Title:
- Iron abundances of red giants in Carina gal.
- Short Name:
- J/PASP/124/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed accurate iron abundance measurements for 44 red giants (RGs) in the Carina dwarf spheroidal (dSph) galaxy. We used archival, high-resolution spectra (R~38000) collected with UVES at ESO/VLT either in slit mode (five RGs) or in fiber mode (39 RGs, FLAMES/GIRAFFE-UVES). The sample is more than a factor of 4 larger than any previous spectroscopic investigation of stars in dSphs based on high-resolution (R>=38000) spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/790/73
- Title:
- Iron and alpha abundance of RGBs in M31 satellites
- Short Name:
- J/ApJ/790/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present alpha to iron abundance ratios for 226 individual red giant branch stars in nine dwarf galaxies of the Andromeda (M31) satellite system. The abundances are measured from the combined signal of Mg, Si, Ca, and Ti lines in Keck/DEIMOS medium-resolution spectra. This constitutes the first large sample of alpha abundance ratios measured in the M31 satellite system. The dwarf galaxies in our sample exhibit a variety of alpha abundance ratios, with the average values in each galaxy ranging from approximately solar ([{alpha}/Fe] ~ + 0.0) to alpha-enhanced ([{alpha}/Fe] ~ + 0.5). These variations do not show a correlation with internal kinematics, environment, or stellar density. We confirm radial gradients in the iron abundance of two galaxies out of the five with sufficient data (NGC 185 and And II). There is only tentative evidence for an alpha abundance radial gradient in NGC 185. We homogeneously compare our results to the Milky Way classical dwarf spheroidals, finding evidence for wider variation in average alpha abundance. In the absence of chemical abundances for the M31 stellar halo, we compare to the Milky Way stellar halo. A stellar halo comprised of disrupted M31 satellites is too metal-rich and inconsistent with the Milky Way halo alpha abundance distribution even if considering only satellites with predominantly old stellar populations. The M31 satellite population provides a second system in which to study chemical abundances of dwarf galaxies and reveals a wider variety of abundance patterns than the Milky Way.
