Selected Research Highlights

The X-ray Luminosity Function of the Northern Disk of M31

We analyzed NuSTAR observations of the northern disk of M31 to create and fit the first hard (12-25 keV) band cumulative X-ray Luminosity Function (XLF) for M31. Contrary to some prior broadband XLF measurements in M31 and other galaxies, we do not find statistically significant evidence of a break in the XLF, and instead find it to be best fit by a single power law. We create additional XLFs separating between XRBs in globular clusters vs in the field, and find statistically distinct shapes, with the globular cluster XLF flatter than that for the field. We also use tentative classifications of the compact objects in M31 XRBs to create preliminary XLFs separated by compact object type, although the small sample size in the black hole XLF does not allow us to make any confident assertions about possible differences in shape between BH and NS XLFs, although the preliminary fits do appear distinct in shape. doi: 10.3847/1538-4357/ad4da4

All the Luminous X-ray Binaries in M31: 825 ks of New Data from NuSTAR

Motivated by the desire to create a hard band XLF that covers both the northern and southern disk of M31, obtain complete coverage of all high luminosity sources in the hard band, classify 20-60 additional compact objects in XRBs, and build upon the existing multiwavelength coverage from the The Panchromatic Hubble Andromeda Southern Treasury (PHAST), we wrote a successful NuSTAR large program proposal totaling 825 ks of observations between 6 fields in the southern disk of M31 and 3 in the northern disk.

The 9 fields associated with our large program in the south (red, ~35ks each) and north (blue, ~120ks each) are shown relative to the UV (GALEX) image of M31 and previously existing (white) NuSTAR fields. A background-subtracted and exposure-corrected NuSTAR mosaic is slightly enlarged above the GALEX image, illustrating the brightest detected sources in all fields.

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