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Variability of massive stars in M31 from the Palomar Transient Factory

Soraisam, Monika D. and Bildsten, Lars and Drout, Maria R. and Prince, Thomas A. and Kupfer, Thomas and Masci, Frank and Laher, Russ R. and Kulkarni, Shrinivas R. (2020) Variability of massive stars in M31 from the Palomar Transient Factory. Astrophysical Journal, 893 (1). Art. No. 11. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20191007-150028591

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Abstract

Using data from the (intermediate) Palomar Transient Factory (iPTF), we characterize the time variability of ≈500 massive stars in M31. Our sample is those stars that are spectrally typed by Massey and collaborators, including Luminous Blue Variables, Wolf–Rayets, and warm and cool supergiants. We use the high-cadence, long-baseline (≈5 yr) data from the iPTF survey, coupled with data-processing tools that model complex features in the light curves. We find widespread photometric (R-band) variability in the upper Hertzsprung Russell diagram (or CMD) with an increasing prevalence of variability with later spectral types. Red stars (V − I > 1.5) exhibit larger amplitude fluctuations than their bluer counterparts. We extract a characteristic variability timescale, t_(ch), via wavelet transformations that are sensitive to both continuous and localized fluctuations. Cool supergiants are characterized by longer timescales (>100 days) than the hotter stars. The latter have typical timescales of tens of days but cover a wider range, from our resolution limit of a few days to longer than 100 days. Using a 60 night block of data straddling two nights with a cadence of around 2 minutes, we extracted t_(ch) in the range 0.1–10 days with amplitudes of a few percent for 13 stars. Though there is broad agreement between the observed variability characteristics in the different parts of the upper CMD with theoretical predictions, detailed comparison requires models with a more comprehensive treatment of the various physical processes operating in these stars, such as pulsation, subsurface convection, and the effect of binary companions.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ab7b7bDOIArticle
https://arxiv.org/abs/1908.02439arXivDiscussion Paper
ORCID:
AuthorORCID
Drout, Maria R.0000-0001-7081-0082
Prince, Thomas A.0000-0002-8850-3627
Kupfer, Thomas0000-0002-6540-1484
Masci, Frank0000-0002-8532-9395
Laher, Russ R.0000-0003-2451-5482
Kulkarni, Shrinivas R.0000-0001-5390-8563
Additional Information:© 2020 The American Astronomical Society. Received 2019 August 6; revised 2020 February 21; accepted 2020 February 26; published 2020 April 8. M.D.S. is supported by the Illinois Survey Science Fellowship of the Center for Astrophysical Surveys at the University of Illinois at Urbana-Champaign. This research was supported in part by the National Science Foundation through grant PHY-1748958 at the KITP and benefited from interactions that were funded by the Gordon and Betty Moore Foundation through grant GBMF5076. M.D.S. thanks Chien-Hsiu Lee for helpful discussions on observational studies of stellar variability, as well as Niels Oppermann for insights regarding proper applications of signal analysis tools. We also thank Charlie Conroy and Yan-Fei Jiang for discussions, and the latter for providing his simulation data. M.R.D. acknowledges support from the Dunlap Institute at the University of Toronto and the Canadian Institute for Advanced Research (CIFAR). This work was based on observations obtained with the 48 inch Samuel Oschin Telescope at the Palomar Observatory as part of the Palomar Transient Factory project. Operations were conducted by Caltech Optical Observatories and data processing by IPAC. We thank Xiaodian Chen for helpful comments on the period–luminosity relation of contact binaries. Software: numpy (van der Walt et al. 2011), scipy (Virtanen et al. 2020), astropy (Astropy Collaboration et al. 2013), pyfits, pandas (McKinney 2010), mpi4py (Dalcín et al. 2005), matplotlib (Hunter 2007), DAOPHOT (Stetson 1987), DAOGROW (Stetson 1990), NIFTy (Selig et al. 2013).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Palomar Transient Factory
Funders:
Funding AgencyGrant Number
University of Illinois Urbana-ChampaignUNSPECIFIED
NSFPHY-1748958
Gordon and Betty Moore FoundationGBMF5076
Dunlap Institute for Astronomy and AstrophysicsUNSPECIFIED
University of TorontoUNSPECIFIED
Canadian Institute for Advanced Research (CIFAR)UNSPECIFIED
Subject Keywords:Andromeda galaxy ; Massive stars ; Supergiant stars ; Catalogs ; Surveys
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Andromeda Galaxy (39); Massive stars (732); Supergiant stars (1661); Catalogs (205); Surveys (1671)
Record Number:CaltechAUTHORS:20191007-150028591
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20191007-150028591
Official Citation:Monika D. Soraisam et al 2020 ApJ 893 11
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99125
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:07 Oct 2019 22:15
Last Modified:08 Apr 2020 21:07

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