Evidence for Intermediate Polars as the Origin of the Galactic Center Hard X-Ray Emission

Hailey, Charles J.; Mori, Kaya; Perez, K.; Canipe, Alicia M.; Hong, Jaesub; Tomsick, John A.; Boggs, Steven E.; Christensen, Finn Erland; Craig, William W.; Fornasini, Francesca M.; Grindlay, Jonathan E.; Harrison, Fiona A.; Nynka, Melania; Rahoui, Farid; Stern, Daniel; Zhang, Shuo; Zhang, William W.

doi:10.3847/0004-637x/826/2/160

Cited by 65 publications

(99 citation statements)

References 63 publications

(137 reference statements)

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“…The parameters of the IPM model are well constrained by the fit and the white dwarf mass we obtain, M wd = 0.78 +0.10 −0.09 M , is consistent with the typical mass generally observed for white dwarfs in IPs (e.g. Suleimanov et al 2005;Yuasa et al 2010;Hailey et al 2016). In our system, the free parameter α of the reflect model is the inclination of the white dwarf magnetic field compared to the line of sight.…”

Section: Modelsupporting

confidence: 84%

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IGR J18293−1213 is an eclipsing cataclysmic variable

Clavel¹,

Tomsick²,

Bodaghee³

et al. 2016

Mon. Not. R. Astron. Soc.

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Studying the population of faint hard X-ray sources along the plane of the Galaxy is challenging because of high-extinction and crowding, which make the identification of individual sources more difficult. IGR J18293-1213 is part of the population of persistent sources which have been discovered by the INTEGRAL satellite. We report on NuSTAR and Swift/XRT observations of this source, performed on 2015 September 11. We detected three eclipsing intervals in the NuSTAR light curve, allowing us to constrain the duration of these eclipses, ∆t = 30.8−0.0 min, and the orbital period of the system, T = 6.92 ± 0.01 hr. Even though we only report an upper limit on the amplitude of a putative spin modulation, the orbital period and the hard thermal Bremsstrahlung spectrum of IGR J18293-1213 provide strong evidence that this source is a magnetic Cataclysmic Variable (CV). Our NuSTAR and Swift/XRT joint spectral analysis places strong constraints on the white dwarf mass M wd = 0.78Assuming that the mass to radius ratio of the companion star M /R = 1 (solar units) and using T , ∆t and M wd , we derived the mass of the companion star M = 0.82 ± 0.01 M , the orbital separation of the binary system a = 2.14 ± 0.04 R , and its orbital inclination compared to the line of sight i = (72.2 +2.4 −0.0 ) ± 1.0• .

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Section: Modelsupporting

confidence: 84%

“…Suleimanov et al 2005;Yuasa et al 2010;Hailey et al 2016). The average X-ray luminosity of this bright population is L 0.1−100keV ∼ 2 × 10 34 erg s…”

Section: Discussionmentioning

confidence: 99%

IGR J18293−1213 is an eclipsing cataclysmic variable

Clavel¹,

Tomsick²,

Bodaghee³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…In contrast, Xu et al (2016) studied the Fe K lines of CVs and the GRXE, and found the properties of the latter to be consistent with those of dwarf novae. Hailey et al (2016), on the other hand, found that the Galactic center diffuse X-rays to have spectral characteristics similar to those of field IPs, but again required IP XLF to extend to lower luminosities than found in the solar neighborhood.…”

Section: X-rays From the Galactic Ridge Bulge And Center Regionsmentioning

confidence: 99%

X-Ray Emissions from Accreting White Dwarfs: A Review

Mukai

2017

PASP

233

212

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Interacting binaries in which a white dwarf accretes material from a companion-cataclysmic variables (CVs) in which the mass donor is a Roche-lobe filling star on or near the main sequence, and symbiotic stars in which the mass donor is a late type giant-are relatively commonplace. They display a wide range of behaviors in the optical, X-rays, and other wavelengths, which still often baffle observers and theorists alike. Here I review the existing body of research on X-ray emissions from these objects for the benefits of both experts and newcomers to the field. I provide introductions to the past and current X-ray observatories, the types of known X-ray emissions from these objects, and the data analysis techniques relevant to this field. I then summarize of our knowledge regarding the X-ray emissions from magnetic CVs, non-magnetic CVs and symbiotic stars, and novae in eruption. I also discuss space density and the X-ray luminosity functions of these binaries and their contribution to the integrated X-ray emission from the Galaxy. I then discuss open questions and future prospects.

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“…Previously, both low-energy (<10 keV) and high-energy (>10 keV) observations were attributed to a dominant population of magnetically accreting white dwarf (WD) binaries, in particular intermediate polars (IPs), with an average WD mass of M W D ≈ 0.5 − 0.66M Krivonos et al 2007;Yuasa et al 2012;Heard & Warwick 2013). However, NuSTAR observations of the inner 100 pc now indicate that the Galactic center is dominated by heavier IPs with M W D > 0.8M (Perez et al 2015;Hailey et al 2016;Hong et al 2016). In addition, Suzaku measurements have revealed differing Fe line intensities in the three regions, indicating a changing underlying source population (Xu et al 2016;Yamauchi et al 2016;Koyama 2018;Nobukawa et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Galactic Bulge Diffuse Emission in Broadband X-Rays with NuSTAR

Perez

Krivonos

Wik

2019

ApJ

Self Cite

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The diffuse hard X-ray emission that fills the Galactic center, bulge, and ridge is believed to arise from unresolved populations of X-ray binary systems. However, the identity of the dominant class of accreting objects in each region remains unclear. Recent studies of Fe line properties and the lowenergy (< 10 keV) X-ray continuum of the bulge indicate a major population fraction of non-magnetic cataclysmic variables (CVs), in particular quiescent dwarf novae. This is in contrast to previous highenergy (> 10 keV) X-ray measurements of the bulge and ridge, which indicate a dominant population of magnetic CVs, in particular intermediate polars. In addition, NuSTAR broad-band measurements have uncovered a much heavier intermediate polar population in the central ∼ 100 pc than previously assumed, raising the possibility that some fraction of this population extends further from the center.Here we use NuSTAR's large aperture for unfocused photons and its broad-band X-ray range to probe the diffuse continuum of the inner ∼1-3 • of the Galactic bulge. This allows us to constrain possible multi-temperature components of the spectrum, such as could indicate a mixture of soft and hard populations. Our emissivity is consistent with previous hard X-ray measurements in the bulge and ridge, with the diffuse X-ray luminosity tracing the stellar mass. The spectrum is well-described by a single-temperature thermal plasma with kT ≈ 8 keV, with no significant emission above 20 keV. This supports that the bulge is dominated by quiescent dwarf novae; we find no evidence of a significant intermediate polar population in the hard X-ray band.

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Evidence for Intermediate Polars as the Origin of the Galactic Center Hard X-Ray Emission

Cited by 65 publications

References 63 publications

IGR J18293−1213 is an eclipsing cataclysmic variable

IGR J18293−1213 is an eclipsing cataclysmic variable

X-Ray Emissions from Accreting White Dwarfs: A Review

The Galactic Bulge Diffuse Emission in Broadband X-Rays with NuSTAR

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