J/ApJ/908/87 182 RSGs and OB-stars in M31 and M33 (Neugent, 2021)
The Red Supergiant Binary Fraction as a Function of Metallicity in M31 and M33.
Neugent K.F.
<Astrophys. J., 908, 87 (2021)>
=2021ApJ...908...87N 2021ApJ...908...87N
ADC_Keywords: Stars, OB; Stars, supergiant; Stars, double and multiple; Colors;
Optical
Keywords: Massive stars ; Red supergiant stars ; Binary stars ;
Andromeda Galaxy ; Triangulum Galaxy ; Metallicity ; OB stars
Abstract:
Recent work measuring the binary fraction of evolved red supergiants
(RSGs) in the Magellanic Clouds points to a value between 15% and 30%,
with the majority of the companions being unevolved B-type stars as
dictated by stellar evolution. Here I extend this research to the
Local Group galaxies M31 and M33 and investigate the RSG binary
fraction as a function of metallicity. Recent near-IR photometric
surveys of M31 and M33 have led to the identification of a complete
sample of RSGs down to a limiting logL/L☉≥4.2. To determine the
binary fraction of these M31 and M33 RSGs, I used a combination of
newly obtained spectroscopy to identify single RSGs and RSG+OB
binaries, as well as archival UV, visible, and near-IR photometry to
probabilistically classify RSGs as either single or binary based on
their colors. I then adjusted the observed RSG+OB binary fraction to
account for observational biases. The resulting RSG binary fraction in
M33 shows a strong dependence on galactocentric distance, with the
inner regions having a much higher binary fraction
(41.2-7.3+12.0%) than the outer regions (15.9-1.9+12.4%). Such
a trend is not seen in M31; instead, the binary fraction in lightly
reddened regions remains constant at 33.5-5.0+8.6% . I conclude
that the changing RSG binary fraction in M33 is due to a metallicity
dependence, with higher-metallicity environments having higher RSG
binary fractions. This dependence most likely stems not from changes
in the physical properties of RSGs due to metallicity but from changes
in the parent distribution of OB binaries.
Description:
Observations were carried out using the multiobject, fiber-fed
spectrograph Hectospec on the 6.5m MMT located near Tucson. The M31
field was observed on UT 2019 September 5 and the M33 field was
observed on UT 2019 October 22 through clear sky conditions with
exposure times of 3x3000s. The data were taken with the 270line/mm
grating that yields a spectral coverage from 3700 to 9000Å. Each of
the 300 fibers is 250um, which provides a spectral resolution of
6Å.
Objects:
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RA (2000) DE Designation(s)
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00 42 44.33 +41 16 07.5 M31 = 2C 56
01 33 50.89 +30 39 36.6 M33 = 1AXG J013351+3039
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 90 182 *Spectroscopically observed M31 and M33 stars
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Note on table1.dat : All photometry is from the LGGS;
Massey+, 2006, J/AJ/131/2478.
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/501/153 : VRB photometry of red supergiants (Massey 1998)
J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)
J/AJ/134/2474 : Ha emission-line stars in 7 dwarfs galaxies (Massey+, 2007)
J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011)
J/ApJ/750/97 : The yellow and red supergiants of M33 (Drout+, 2012)
J/ApJ/759/11 : Wolf-Rayet content of M31 (Neugent+, 2012)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/ApJ/758/133 : Metallicity profile of M31 HII regions & PNe (Sanders+, 2012)
J/A+A/550/A107 : RV catalogue of O stars in 30 Doradus (Sana+, 2013)
J/ApJ/789/10 : M33 WR and Of-type Stars (Neugent+, 2014)
J/A+A/578/A3 : Survey of supergiants in the MCs (Gonzalez-Fernandez+, 2015)
J/ApJ/826/224 : RSG and foreground candidates in M31 (Massey+, 2016)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/ApJ/875/124 : Binary red supergiants. II. B-type companions (Neugent+, 2019)
J/A+A/624/A129 : 30 Dor red supergiant stars radial velocities (Patrick+, 2019)
J/A+A/629/A91 : A source catalog for the SMC (Yang+, 2019)
J/ApJ/900/118 : RSGs in the LMC & sp. follow-up for LMC & SMC (Neugent+, 2020)
J/ApJ/889/44 : UKIRT obs. of red supergiants in M31 (Neugent+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- LGGS Local Group Galaxy Survey designation
27- 28 I2 h RAh [0/1] Hour of Right Ascension (J2000)
30- 31 I2 min RAm Minute of Right Ascension (J2000)
33- 37 F5.2 s RAs Second of Right Ascension (J2000)
39 A1 --- DE- [+] Sign of the Declination (J2000)
40- 41 I2 deg DEd [30/42] Degree of Declination (J2000)
43- 44 I2 arcmin DEm Arcminute of Declination (J2000)
46- 49 F4.1 arcsec DEs Arcsecond of Declination (J2000)
51- 56 F6.3 mag Vmag [17.2/20.4] Apparent V band magnitude
58- 63 F6.3 mag B-V [-0.2/2.18] The (B-V) color
65- 70 F6.3 mag U-B [-1.2/0.58] The (U-B) color
72- 77 F6.3 mag V-R [-0.13/1.42] The (V-R) color
79- 84 F6.3 mag R-I [-0.23/1.55] The (R-I) color
86- 90 A5 --- Class Classification; OB, RSG or RSG+B
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 12-Feb-2024