- ID:
- ivo://CDS.VizieR/J/ApJ/703/420
- Title:
- Red supergiants in M31
- Short Name:
- J/ApJ/703/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red supergiants (RSGs) are a short-lived stage in the evolution of moderately massive stars (10-25M_{sun}_), and as such their location in the H-R diagram provides an exacting test of stellar evolutionary models. Since massive star evolution is strongly affected by the amount of mass loss a star suffers, and since the mass-loss rates depend upon metallicity, it is highly desirable to study the physical properties of these stars in galaxies of various metallicities. Here we identify a sample of RSGs in M31, the most metal-rich of the Local Group galaxies. We determine the physical properties of these stars using both moderate resolution spectroscopy and broadband V-K photometry. We find that on average the RSGs of our sample are variable in V by 0.5mag, smaller but comparable to the 0.9mag found for Magellanic Cloud (MC) RSGs. No such variability is seen at K, also in accord with what we know of Galactic and MC RSGs.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/126/2867
- Title:
- Red supergiants in Magellanic Clouds
- Short Name:
- J/AJ/126/2867
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the red supergiant (RSG) content of the SMC and LMC using multiobject spectroscopy on a sample of red stars previously identified by BVR CCD photometry. We obtained high-accuracy (<1km/s) radial velocities for 118 red stars seen toward the SMC and 167 red stars seen toward the LMC, confirming most of these (89% and 95%, respectively) as red supergiants. Spectral types were also determined for most of these RSGs.
- ID:
- ivo://CDS.VizieR/J/ApJ/671/781
- Title:
- Red supergiants in Sct-Cru Galactic arm
- Short Name:
- J/ApJ/671/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the unprecedented red supergiant (RSG) population of a massive young cluster, located at the base of the Scutum-Crux Galactic arm. We identify candidate cluster RSGs based on 2MASS photometry and medium-resolution spectroscopy. With follow-up high-resolution spectroscopy, we use CO band-head equivalent width and high-precision radial velocity measurements to identify a core grouping of 26 physically associated RSGs-the largest such cluster known to date.
- ID:
- ivo://CDS.VizieR/J/AJ/161/79
- Title:
- Red supergiant stars in M31 and M33
- Short Name:
- J/AJ/161/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify red supergiants (RSGs) in our spiral neighbors M31 and M33 using near-IR (NIR) photometry complete to a luminosity limit of logL/L{odot}=4.0. Our archival survey data cover 5{deg}^2^ of M31, and 3{deg}^2^ for M33, and are likely spatially complete for these massive stars. Gaia is used to remove foreground stars, after which the RSGs can be separated from asymptotic giant branch (AGB) stars in the color-magnitude diagram. The photometry is used to derive effective temperatures and bolometric luminosities via MARCS stellar atmosphere models. The resulting H-R diagrams show superb agreement with the evolutionary tracks of the Geneva evolutionary group. Our census includes 6400 RSGs in M31 and 2850 RSGs in M33 within their Holmberg radii; by contrast, only a few hundred RSGs are known so far in the Milky Way. Our catalog serves as the basis for a study of the RSG binary frequency being published separately, as well as future studies relating to the evolution of massive stars. Here we use the matches between the NIR- selected RSGs and their optical counterparts to show that the apparent similarity in the reddening of OB stars in M31 and M33 is the result of Malmquist bias; the average extinction in M31 is likely higher than that of M33. As expected, the distribution of RSGs follows that of the spiral arms, while the much older AGB population is more uniformly spread across each galaxy's disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/53
- Title:
- Red supergiant stars in the LMC. I.
- Short Name:
- J/ApJ/727/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From previous samples of red supergiants (RSGs) by various groups, 191 objects are assembled to compose a large sample of RSG candidates in LMC. For 189 of them, the identity as an RSG is verified by their brightness and color indexes in several near- and mid-infrared bands related to the Two Micron All Sky Survey (2MASS) JHKs bands and the Spitzer/IRAC and Spitzer/MIPS bands. From the visual time-series photometric observations by the ASAS and MACHO projects which cover nearly 8-10 years, the period and amplitude of light variation are analyzed carefully using both the phase dispersion minimization and Period04 (Lenz, 2004CoAst.144...41L) methods.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A175
- Title:
- Red supergiant stars in the LMC. II.
- Short Name:
- J/A+A/616/A175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The characteristics of infrared properties and mid-infrared (MIR) variability of red supergiant (RSG) stars in the Large Magellanic Cloud (LMC) are analyzed based on 12 bands of near-infrared (NIR) to MIR co-added data from 2MASS, Spitzer and WISE, and ~6.6 years of MIR time-series data collected by the ALLWISE and NEOWISE-R projects. 773 RSGs candidates are compiled from the literature and verified by using the color-magnitude diagram (CMD), spectral energy distribution (SED) and MIR variability. About 15% of valid targets in the IRAC1-IRAC2/IRAC2-IRAC3 diagram may show Polycyclic Aromatic Hydrocarbon (PAH) emission. We show that arbitrary dereddening Q parameters related to the IRAC4, S9W, WISE3, WISE4 and MIPS24 bands could be constructed based on a precise measurement of MIR interstellar extinction law. Several peculiar outliers in our sample are discussed, in which one outlier might be a RSG right before the explosion or an extreme asymptotic giant branch (AGB) star in the very late evolutionary stage based on the MIR spectrum and photometry. There are 744 identified RSGs in the final sample having both the WISE1- and WISE2-band time-series data. The results show that the MIR variability is increasing along with the increasing of brightness. There is a relatively tight correlation between the MIR variability, mass loss rate (MLR; in terms of K_S-WISE3 color) and the warm dust/continuum (in terms of WISE4 magnitude/flux), where the MIR variability is evident for the targets with K_S-WISE3>1.0mag and WISE4<6.5mag, while the rest of the targets show much smaller MIR variability. The MIR variability is also correlated with the MLR for which targets with larger variability also show larger MLR with an approximate upper limit of -6.1M_{sun}_/yr. The variability and luminosity may both be important for the MLR since the WISE4-band flux is increasing exponentially along with the degeneracy of luminosity and variability. The identified RSG sample has been compared with the theoretical evolutionary models and shown that the discrepancy between observation and evolutionary models can be mitigated by considering both variability and extinction.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/35
- Title:
- Red supergiant stars in the SMC. II.
- Short Name:
- J/ApJ/754/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The characteristics of light variation of red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) are analyzed based on the nearly 8-10 year data collected by the ASAS and MACHO projects. The 126 identified RSGs are classified into five categories accordingly: 20 with poor photometry, 55 with no reliable period, 6 with semi-regular variation, 15 with a long secondary period (LSP) and distinguishable short period, and 30 with only an LSP. For the semi-regular variables and the LSP variables with distinguishable short period, the K_S_-band period-luminosity (P-L) relation is analyzed and compared with that of the Galaxy, the Large Magellanic Cloud, and M33. It is found that the RSGs in these galaxies obey a similar P-L relation except for those in the Galaxy. In addition, the P-L relations in the infrared bands, namely, the 2MASS JHK_S_, Spitzer/IRAC, and Spitzer/MIPS 24 {mu}m bands, are derived with high reliability. The best P-L relation occurs in the Spitzer/IRAC [3.6] and [4.5] bands. Based on the comparison with the theoretical calculation of the P-L relation, the mode of pulsation of RSGs in the SMC is suggested to be the first-overtone radial mode.
- ID:
- ivo://CDS.VizieR/J/AJ/162/150
- Title:
- Resolving circumstellar environment of MWC137 .II.
- Short Name:
- J/AJ/162/150
- Date:
- 14 Mar 2022 06:35:34
- Publisher:
- CDS
- Description:
- The Galactic B[e] supergiant MWC137 is surrounded by a large-scale optical nebula. To shed light on the physical conditions and kinematics of the nebula, we analyze the optical forbidden emission lines [NII] {lambda}{lambda}6548,6583 and [SII] {lambda}{lambda}6716,6731 in long-slit spectra taken with ALFOSC at the Nordic Optical Telescope. The radial velocities display a complex behavior but, in general, the northern nebular features are predominantly approaching while the southern ones are mostly receding. The electron density shows strong variations across the nebula with values spreading from about zero to ~800cm^-3^. Higher densities are found closer to MWC137 and in regions of intense emission, whereas in regions with high radial velocities the density decreases significantly. We also observe the entire nebula in the two [SII] lines with the scanning Fabry-Perot interferometer attached to the 6m telescope of the Special Astrophysical Observatory. These data reveal a new bow-shaped feature at PA=225{deg}-245{deg} and a distance 80" from MWC137. A new H{alpha} image has been taken with the Danish 1.54m telescope on La Silla. No expansion or changes in the nebular morphology appear within 18.1yr. We derive a mass of 37_-5_^+9^M{sun} and an age of 4.7{+/-}0.8Myr for MWC137. Furthermore, we detect a period of 1.93d in the time series photometry collected with the TESS satellite, which could suggest stellar pulsations. Other, low-frequency variability is seen as well. Whether these signals are caused by internal gravity waves in the early-type star or by variability in the wind and circumstellar matter currently cannot be distinguished.
- ID:
- ivo://CDS.VizieR/J/A+A/317/871
- Title:
- Revised spectral types of B-supergiants in the SMC
- Short Name:
- J/A+A/317/871
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The problem of the classification of metal poor stars, such as occur in the Small Magellanic Cloud (SMC), is discussed with reference to the applicability of the MK system in such an environment. An alternative method is presented here and applied to B-type supergiants in the SMC. A local reference system is first devised and then a transformation to MK spectral types is determined by comparing the trends of metal line strengths in these two systems. For the determination of the luminosity class, we emphasize the need to use the hydrogen Balmer line strengths independently of metal line-strength considerations. This method is used to determine new spectral types for 64 supergiants in the SMC, 75% of the sample requiring classifications different from previous findings. These new types result in much improved line strength - spectral type correlations for He, C, N, O, Mg and Si. Corresponding changes in the distribution of these stars in the Hertzsprung-Russell diagram of the SMC reveal more clearly than before the existence of a ridge which may be the SMC analogue of a similar feature found for the LMC by Fitzpatrick & Garmany (1990ApJ...363..119F). The group of very luminous supergiants lying above this ridge includes the LBV AV415 (R40), a property which this object has in common with LBVs in the Large Magellanic Cloud. Also, for the first time, clear examples of BN/BC supergiants are found in the SMC.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A125
- Title:
- Rigel K-band temporal monitoring
- Short Name:
- J/A+A/566/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Luminous BA-type supergiants are the brightest stars in the visible that can be observed in distant galaxies and are potentially accurate distance indicators. The impact of the variability of the stellar winds on the distance determination remains poorly understood. Our aim is to probe the inhomogeneous structures in the stellar wind using spectro-interferometric monitoring. We present a spatially resolved, high-spectral resolution (R=12000) K-band temporal monitoring of the bright supergiant {beta} Orionis (Rigel, B8 Iab) using Amber at the Very Large Telescope Interferometer (VLTI). Rigel was observed in the Br{gamma} line and its nearby continuum once per month over 3 months in 2006-2007, and 5 months in 2009-2010. These unprecedented observations were complemented by contemporaneous optical high-resolution spectroscopy. We analyse the near-IR spectra and visibilities with the 1D non-LTE radiative-transfer code CMFGEN. The differential and closure phase signals are evidence of asymmetries that are interpreted as perturbations of the wind.
