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Spectral Evolution of the Ultraluminous X-Ray Sources M82 X-1 and X-2
- Source :
- Astrophys.J., Astrophys.J., 2020, 889 (1), pp.71. ⟨10.3847/1538-4357/ab629a⟩
- Publication Year :
- 2020
- Publisher :
- American Astronomical Society, 2020.
-
Abstract
- M82 hosts two well-known ultraluminous X-ray sources (ULXs). X-1, an intermediate-mass black hole (IMBH) candidate, and X-2, an ultraluminous X-ray pulsar (ULXP). Here we present a broadband X-ray spectral analysis of both sources based on ten observations made simultaneously with Chandra and NuSTAR. Chandra provides the high spatial resolution to resolve the crowded field in the 0.5--8 keV band, and NuSTAR provides the sensitive hard X-ray spectral data, extending the bandpass of our study above 10 keV. The observations, taken in the period 2015--2016, cover a period of flaring from X-1, allowing us to study the spectral evolution of this source with luminosity. During four of these observations, X-2 was found to be at a low flux level, allowing an unambiguous view of the emission from X-1. We find that the broadband X-ray emission from X-1 is consistent with that seen in other ULXs observed in detail with NuSTAR, with a spectrum that includes a broadened disk-like component and a high-energy tail. We find that the luminosity of the disk scales with inner disk temperature as L~T^-3/2 contrary to expectations of a standard accretion disk and previous results. These findings rule out a thermal state for sub-Eddington accretion and therefore do not support M82 X-1 as an IMBH candidate. We also find evidence that the neutral column density of the material in the line of sight increases with L$_X$, perhaps due to an increased mass outflow with accretion rate. For X-2, we do not find any significant spectral evolution, but we find the spectral parameters of the phase-averaged broadband emission are consistent with the pulsed emission at the highest X-ray luminosities.<br />In press at ApJ
- Subjects :
- High Energy Astrophysical Phenomena (astro-ph.HE)
Physics
Line-of-sight
010504 meteorology & atmospheric sciences
Accretion (meteorology)
Astrophysics::High Energy Astrophysical Phenomena
FOS: Physical sciences
Flux
Astronomy and Astrophysics
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
01 natural sciences
Electromagnetic radiation
Luminosity
Black hole
Pulsar
Space and Planetary Science
0103 physical sciences
M82 X-1
Astrophysics - High Energy Astrophysical Phenomena
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
010303 astronomy & astrophysics
Astrophysics::Galaxy Astrophysics
0105 earth and related environmental sciences
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- Astrophys.J., Astrophys.J., 2020, 889 (1), pp.71. ⟨10.3847/1538-4357/ab629a⟩
- Accession number :
- edsair.doi.dedup.....f06f657fb6712beeb3420545951f5d3d