scholarly journals Testing Evolutionary Models with Red Supergiant and Wolf–Rayet Populations

2021 ◽  
Vol 922 (2) ◽  
pp. 177
Author(s):  
Philip Massey ◽  
Kathryn F. Neugent ◽  
Trevor Z. Dorn-Wallenstein ◽  
J. J. Eldridge ◽  
E. R. Stanway ◽  
...  
Keyword(s):  
Near Infrared ◽  
Relative Number ◽  
Interference Filter ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Evolutionary Models ◽  
Image Subtraction ◽  
Single Star ◽  
Red Supergiants ◽  
Effective Temperatures

Abstract Despite the many successes that modern massive star evolutionary theory has enjoyed, reproducing the apparent trend in the relative number of red supergiants (RSGs) and Wolf–Rayet (WR) stars has remained elusive. Previous estimates show the RSG/WR ratio decreasing strongly with increasing metallicity. However, the evolutionary models have always predicted a relatively flat distribution for the RSG/WR ratio. In this paper we reexamine this issue, drawing on recent surveys for RSGs and WRs in the Magellanic Clouds, M31, and M33. The RSG surveys have used Gaia astrometry to eliminate foreground contamination and have separated RSGs from asymptotic giant branch stars using near-infrared colors. The surveys for WRs have utilized interference-filter imaging, photometry, and image subtraction techniques to identify candidates, which have then been confirmed spectroscopically. After carefully matching the observational criteria to the models, we now find good agreement in both the single-star Geneva and binary BPASS models with the new observations. The agreement is better when we shift the RSG effective temperatures derived from J − Ks photometry downwards by 200 K in order to agree with the Levesque TiO effective temperature scale. In an appendix we also present a source list of RSGs for the SMC which includes effective temperatures and luminosities derived from near-infrared 2MASS photometry, in the same manner as used for the other galaxies.

scholarly journals The Physical Properties of Red Supergiants: Comparing Theory and Observations

2007 ◽  
Vol 3 (S250) ◽  
pp. 97-110 ◽  
Author(s):  
Philip Massey ◽  
Emily M. Levesque ◽  
Bertrand Plez ◽  
Knut A. G. Olsen
Keyword(s):  
Physical Properties ◽  
Milky Way ◽  
Massive Stars ◽  
Stellar Atmospheres ◽  
Circumstellar Dust ◽  
Evolutionary Models ◽  
Dust Source ◽  
Look Back ◽  
Red Supergiants ◽  
Effective Temperatures

AbstractRed supergiants (RSGs) are an evolved stage in the life of intermediate massive stars (≤ 25 M⊙). For many years, their location in the H-R diagram was at variance with the evolutionary models. Using the MARCS stellar atmospheres, we have determined new effective temperatures and bolometric luminosities for RSGs in the Milky Way, LMC, and SMC, and our work has resulted in much better agreement with the evolutionary models. We have also found evidence of significant visual extinction due to circumstellar dust. Although in the Milky Way the RSGs contribute only a small fraction (< 1%) of the dust to the interstellar medium (ISM), in starburst galaxies or galaxies at large look-back times, we expect that RSGs may be the main dust source. We are in the process of extending this work now to RSGs of higher and lower metallicities using the galaxies M31 and WLM.

scholarly journals High-cadence, early-time observations of core-collapse supernovae from the TESS prime mission

2020 ◽  
Vol 500 (4) ◽  
pp. 5639-5656
Author(s):  
P J Vallely ◽  
C S Kochanek ◽  
K Z Stanek ◽  
M Fausnaugh ◽  
B J Shappee
Keyword(s):  
Near Infrared ◽  
Early Time ◽  
Light Curves ◽  
Core Collapse ◽  
Type Ii ◽  
Strong Correlations ◽  
Image Subtraction ◽  
Red Supergiants ◽  
Ultraviolet Observations ◽  
Analytic Models

ABSTRACT We present observations from the Transiting Exoplanet Survey Satellite (TESS) of twenty bright core-collapse supernovae with peak TESS-band magnitudes ≲18 mag. We reduce this data with an implementation of the image subtraction pipeline used by the All-Sky Automated Survey for Supernovae (ASAS-SN) optimized for use with the TESS images. In empirical fits to the rising light curves, we do not find strong correlations between the fit parameters and the peak luminosity. Existing semi-analytic models fit the light curves of the Type II supernovae well, but do not yield reasonable estimates of the progenitor radius or explosion energy, likely because they are derived for use with ultraviolet observations while TESS observes in the near-infrared. If we instead fit the data with numerically simulated light curves, the rising light curves of the Type II supernovae are consistent with the explosions of red supergiants. While we do not identify shock breakout emission for any individual event, when we combine the fit residuals of the Type II supernovae in our sample, we do find a &gt;5σ flux excess in the ∼1 d before the start of the light-curve rise. It is likely that this excess is due to shock breakout emission, and that during its extended mission TESS will observe a Type II supernova bright enough for this signal to be detected directly.

scholarly journals Rapid evolution of [WC] stars in the Magellanic Clouds

2020 ◽  
Vol 642 ◽  
pp. A71
Author(s):  
Marcin Hajduk
Keyword(s):  
South African ◽  
Rapid Evolution ◽  
Planetary Nebulae ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Evolutionary Models ◽  
Heating Rates ◽  
Giant Branch Stars ◽  
Central Stars

We obtained new spectra of fourteen Magellanic Cloud planetary nebulae with the South African Large Telescope to determine heating rates of their central stars and to verify evolutionary models of post-asymptotic giant branch stars. We compared new spectra with observations made in previous years. Five planetary nebulae showed an increase in excitation over time. Four of their central stars exhibit [WC] features in their spectra, including three new detections. This raises the total number of [WC] central stars of PNe in the Magellanic Clouds to ten. We compared determined heating rates of the four [WC] central stars with the He-burning post-asymptotic giant branch evolutionary tracks and the remaining star with the H-burning tracks. Determined heating rates are consistent with the evolutionary models for both H and He-burning post-asymptotic giant branch stars. The central stars of the PNe that show the fastest increase of excitation are also the most luminous in the sample. This indicates that [WC] central stars in the Magellanic Clouds evolve faster than H-burning central stars, and they originate from more massive progenitors.

scholarly journals Near-infrared photometric properties of asymptotic giant branch stars in the dwarf irregular galaxy IC 1613

2015 ◽  
Vol 578 ◽  
pp. A51 ◽  
Author(s):  
Sang-Hyun Chun ◽  
MiYoung Jung ◽  
Minhee Kang ◽  
Jae-Woo Kim ◽  
Young-Jong Sohn
Keyword(s):  
Near Infrared ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Irregular Galaxy ◽  
Giant Branch Stars

scholarly journals The Wolf–Rayet Content of the Galaxies of the Local Group and Beyond

Galaxies ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 74 ◽  
Author(s):  
Kathryn Neugent ◽  
Philip Massey
Keyword(s):  
Massive Star ◽  
Local Group ◽  
Large Range ◽  
Binary Star ◽  
Interference Filter ◽  
Relative Importance ◽  
Evolutionary Models ◽  
Image Subtraction ◽  
Current State ◽  
Test Current

Wolf–Rayet stars (WRs) represent the end of a massive star’s life as it is about to turn into a supernova. Obtaining complete samples of such stars across a large range of metallicities poses observational challenges, but presents us with an exacting way to test current stellar evolutionary theories. A technique we have developed and refined involves interference filter imaging combined with image subtraction and crowded-field photometry. This helps us address one of the most controversial topics in current massive star research: the relative importance of binarity in the evolution of massive stars and formation of WRs. Here, we discuss the current state of the field, including how the observed WR populations match with the predictions of both single and binary star evolutionary models. We end with what we believe are the most important next steps in WR research.

scholarly journals The VLT-FLAMES Tarantula Survey

2019 ◽  
Vol 624 ◽  
pp. A128 ◽  
Author(s):  
N. Britavskiy ◽  
D. J. Lennon ◽  
L. R. Patrick ◽  
C. J. Evans ◽  
A. Herrero ◽  
...  
Keyword(s):  
Near Infrared ◽  
Interstellar Extinction ◽  
Large Magellanic Cloud ◽  
Young Star ◽  
Physical Parameters ◽  
Single Star ◽  
Near Ir ◽  
Large Spread ◽  
Red Supergiants ◽  
Young Star Clusters

Aims. We estimate physical parameters for the late-type massive stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud (LMC). Methods. The observational sample comprises 20 candidate red supergiants (RSGs) which are the reddest ((B − V) > 1 mag) and brightest (V < 16 mag) objects in the VFTS. We use optical and near-infrared (near-IR) photometry to estimate their temperatures and luminosities, and introduce the luminosity–age diagram to estimate their ages. Results. We derive physical parameters for our targets, including temperatures from a new calibration of (J − Ks)0 colour for luminous cool stars in the LMC, luminosities from their J-band magnitudes (thence radii), and ages from comparisons with current evolutionary models. We show that interstellar extinction is a significant factor for our targets, highlighting the need to take it into account in the analysis of the physical parameters of RSGs. We find that some of the candidate RSGs could be massive AGB stars. The apparent ages of the RSGs in the Hodge 301 and SL 639 clusters show a significant spread (12–24 Myr). We also apply our approach to the RSG population of the relatively nearby NGC 2100 cluster, finding a similarly large spread. Conclusions. We argue that the effects of mass transfer in binaries may lead to more massive and luminous RSGs (which we call “red stragglers”) than expected from single-star evolution, and that the true cluster ages correspond to the upper limit of the estimated RSG ages. In this way, the RSGs can serve as a new and potentially reliable age tracer in young star clusters. The corresponding analysis yields ages of 24−3+5 Myr for Hodge 301, 22−5+6 Myr for SL 639, and 23−2+4 Myr for NGC 2100.

scholarly journals AGB Stars Interferometric Signatures: Effects of Possible Li-rich Spots

2000 ◽  
Vol 198 ◽  
pp. 476-477
Author(s):  
Patrick de Laverny ◽  
Bruno Lopez
Keyword(s):  
Asymptotic Giant Branch ◽  
Observational Constraints ◽  
Asymptotic Giant Branch Stars ◽  
Evolutionary Models ◽  
Agb Stars ◽  
Giant Branch Stars

We propose to observe Asymptotic Giant Branch stars (AGB) with spectro-differential interferometric techniques in order to find new observational constraints to inner structure and evolutionary models of these stars. We examine the interferometric signatures created by possible heterogeneities on AGB stars surface due to local Li-enrichments or Li-rich spots and find that such heterogeneities, if they exist, could be detected with present or future interferometers.

Chemical abundances of four red supergiants star clusters (RSGCs) in Scutum-Crux arm

2019 ◽  
Vol 14 (S351) ◽  
pp. 189-191
Author(s):  
Sang-Hyun Chun
Keyword(s):  
High Resolution ◽  
Spectral Properties ◽  
Near Infrared ◽  
Milky Way ◽  
Star Clusters ◽  
Chemical Abundances ◽  
Red Supergiants ◽  
Low Metallicity ◽  
Effective Temperatures

AbstractWe investigate the spectral properties of red supergiant stars in the four RSGCs (RSGC2, RSGC3, RSGC4, RSGC5, and Alicante 10) in the Scutum-Crux arm of the Milky Way. The high-resolution (R: 45,000) near-infrared (H and K bands) spectra for 41 red supergiants were obtained using IGRINS at Gemini South telescope. The calibration of effective temperatures and gravities are derived based on the EWTi and EWCO using supergiants in IGIRNS library. The resulted temperatures and gravities are consistent with previous results. Model spectra were synthesized using derived stellar parameters from which we estimate metallicities and chemical abundances like α-elements. In our preliminary result, we find that overall four RSGCs indeed have sub-solar metallicities as already known in previous studies. The metallicity properties of RSGCs are far off the nominal metallicity trend in this region, and this suggests recent low-metallicity gas fueling into the inner disk and bulge.

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