A NuSTAR Census of the X-Ray Binary Population of the M31 Disk

Hannah Moon; Daniel R. Wik; V. Antoniou; M. Eracleous; Ann E. Hornschemeier; Margaret Lazzarini; Bret D. Lehmer; Neven Vulic; Benjamin F. Williams; T. J. Maccarone; K. Pottschmidt; Andrew Ptak; Mihoko Yukita; Andreas Zezas

doi:10.3847/1538-4357/ad4da4

The Astrophysical Journal (Jan 2024)

A NuSTAR Census of the X-Ray Binary Population of the M31 Disk

Hannah Moon,
Daniel R. Wik,
V. Antoniou,
M. Eracleous,
Ann E. Hornschemeier,
Margaret Lazzarini,
Bret D. Lehmer,
Neven Vulic,
Benjamin F. Williams,
T. J. Maccarone,
K. Pottschmidt,
Andrew Ptak,
Mihoko Yukita,
Andreas Zezas

Affiliations

Hannah Moon: ORCiD; Department of Physics & Astronomy, The University of Utah , 115 South 1400 East, Salt Lake City, UT 84112, USA
Daniel R. Wik: ORCiD; Department of Physics & Astronomy, The University of Utah , 115 South 1400 East, Salt Lake City, UT 84112, USA
V. Antoniou: ORCiD; Department of Physics & Astronomy, Texas Tech University , Box 41051, Lubbock, TX 79409-1051, USA; Center for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA
M. Eracleous: ORCiD; Department of Astronomy and Astrophysics and Institute for Gravitation and the Cosmos, The Pennsylvania State University , 525 Davey Lab, University Park, PA 16802, USA
Ann E. Hornschemeier: ORCiD; NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA; The Johns Hopkins University , Homewood Campus, Baltimore, MD 21218, USA
Margaret Lazzarini: ORCiD; Department of Physics & Astronomy, California State University Los Angeles , 5151 State University Drive, Los Angeles, CA 90032, USA
Bret D. Lehmer: ORCiD; Department of Physics, University of Arkansas , 226 Physics Building, 825 West Dickson Street, Fayetteville, AR 72701, USA
Neven Vulic: ORCiD; NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA; Eureka Scientific Inc. , 2452 Delmer Street, Suite 100, Oakland, CA 94602-3017, USA; Department of Astronomy, University of Maryland , College Park, MD 20742-2421, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA
Benjamin F. Williams: ORCiD; Department of Astronomy, Box 351580, University of Washington , Seattle, WA 98195, USA
T. J. Maccarone: Department of Physics & Astronomy, Texas Tech University , Box 41051, Lubbock, TX 79409-1051, USA
K. Pottschmidt: ORCiD; Astroparticle Physics Laboratory, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; CRESST, Center for Space Sciences and Technology, University of Maryland Baltimore County , Baltimore, MD 210250, USA
Andrew Ptak: ORCiD; NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA; The Johns Hopkins University , Homewood Campus, Baltimore, MD 21218, USA
Mihoko Yukita: ORCiD; NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA; The Johns Hopkins University , Homewood Campus, Baltimore, MD 21218, USA
Andreas Zezas: ORCiD; Center for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA; Physics Department, University of Crete , Heraklion, Greece; Institute of Astrophysics , Foundation for Research and Technology-Hellas, N. Plastira 100, Vassilika Vouton, 71110 Heraklion, Greece

DOI: https://doi.org/10.3847/1538-4357/ad4da4
Journal volume & issue: Vol. 970, no. 2
p. 167

Abstract

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Using hard ( E > 10 keV) X-ray observations with NuSTAR, we are able to differentiate between the accretion states, and thus compact object types, of neutron stars (NSs) and black holes (BHs) in X-ray binaries (XRBs) in M31, our nearest Milky Way–type neighbor. Using 10 moderate-depth (20–50 ks) observations of the disk of M31 covering a total of ∼0.45 deg ^2 , we detect 20 sources at 2 σ in the 4–25 keV bandpass, 14 of which we consider to be XRB candidates. This complements an existing, deeper (100–400 ks) survey covering ∼0.2 deg ^2 of the bulge and the northeastern disk. We make tentative classifications of nine of these sources with the use of diagnostic color–intensity and color–color diagrams, which separate sources into various NS and BH regimes, identifying three BHs and six NSs. In addition, we create X-ray luminosity functions (XLFs) for both the full (4–25 keV) and hard (12–25 keV) bands, as well as subpopulations of the full band based on compact object type and association with globular clusters. Our best-fit globular cluster XLF is shallower than the field XLF, and preliminary BH and NS XLFs suggest a difference in shape based on compact object type. We find that the cumulative disk XLFs in the full and hard band are best fit by power laws with indices of 1.32 and 1.28, respectively. This is consistent with models of the Milky Way XLF from Grimm et al., Voss & Ajello, and Doroshenko et al.

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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