NuSTAR view of the central region of M31

Stiele, H.; Kong, Albert

doi:10.1093/mnras/sty106

Cited by 5 publications

(8 citation statements)

References 42 publications

(50 reference statements)

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“…We obtain 2-bounce M31 spectral indices in the range ∼ 1.3-1.7 for the observations in this analysis, consistent with the population of faint X-ray sources in, e.g., Ref. [79]. Since the NuSTAR optics bench blocks the disk of M31, as shown in Fig.…”

Section: E Spectral Fitsupporting

confidence: 89%

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New constraints on sterile neutrino dark matter from NuSTAR M31 observations

et al. 2019

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We use a combined 1.2 Ms of NuSTAR observations of M31 to search for X-ray lines from sterile neutrino dark matter decay. For the first time in a NuSTAR analysis, we consistently take into account the signal contribution from both the focused and unfocused fields of view. We also reduce the modeling systematic uncertainty by performing spectral fits to each observation individually and statistically combining the results, instead of stacking the spectra. We find no evidence of unknown lines, and thus derive limits on the sterile neutrino parameters. Our results place stringent constraints for dark matter masses 12 keV, which reduces the available parameter space for sterile neutrino dark matter produced via neutrino mixing (e.g., in the νMSM) by approximately one-third. Additional NuSTAR observations, together with improved low-energy background modeling, could probe the remaining parameter space in the future. Lastly, we also report model-independent limits on generic dark matter decay rates and annihilation cross sections. I.via a small mixing with active neutrinos [12], which may be enhanced by the presence of primordial lepton asymmetry [13]. As the mixing angle determines both the abundance and decay rate, there is a finite window in the mass-mixing angle parameter plane in which sterile neutrinos could constitute the full DM abundance, thus allowing this scenario to be fully testable. Closing this window would imply additional physics and production mechanisms are needed to make sterile neutrinos a viable DM candidate [14][15][16][17][18][19][20][21]. The existence of sterile neutrino DM could provide strong clues for explaining neutrino mass and baryogenesis [22], such as the scenario advocated in the νMSM model [23][24][25][26].Due to several sensitive X-ray instruments, such as Chandra, Suzaku, XMM-Newton, and INTEGRAL, stringent constraints on X-ray line emission have been obtained using many different observations (e.g., Refs. [27][28][29][30][31][32][33]). Interest in these topics was heightened with the tentative detection of a 3.5-keV line from cluster observations [34], which was followed up by many observational studies . The nature of this line is still inconclusive. The line could be a signature of sterile neutrino DM [57] or other candidates [58][59][60][61][62]. However, as the line flux is weak, astrophysical modeling systematics [37,41] or new astrophysical processes [63,64] could also be the explanation. New detectors [44,56,65,66] or techniques, such as velocity spectroscopy [67,68], are likely required to fully determine its nature. (Recently, Ref. [69] claims that blank-sky observations with XMM-Newton disfavor the DM interpretation of the 3.5-keV line. On the other hand, Ref. [70] claims detection of the 3.5 keV line in the Milky Way halo up to 35 • with XMM-Newton, and arXiv:1901.01262v2 [astro-ph.HE]

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Section: E Spectral Fitsupporting

confidence: 89%

“…We select NuSTAR observations that include at most 1 or 2 resolved X-ray sources in the 2-bounce FOV. We then remove from our analysis all detector pixels correspond- [79] is included in the spectral modeling. Data reduction and analysis are performed with the NuSTAR Data Analysis Software pipeline, NuSTARDAS v1.5.1.…”

Section: B Nustar's View Of M31mentioning

confidence: 99%

New constraints on sterile neutrino dark matter from NuSTAR M31 observations

et al. 2019

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“…Three sources in our sample were investigated in detail by Stiele & Kong (2018) in a NuSTAR survey of the central region of M31. This study was designed to overlap with a previous XMM-Newton survey of M31 (Stiele et al 2011).…”

Section: Comparison With Other Hard X-ray Observations Of M31mentioning

confidence: 99%

“…This study was designed to overlap with a previous XMM-Newton survey of M31 (Stiele et al 2011). Stiele & Kong (2018) use hardness ratios, to classify four X-ray sources previously classified only as "hard" using XMM-Newton data as X-ray binaries. Two of these new XRB candidates are in our sample: NuSTAR sources 47 and 65.…”

Section: Comparison With Other Hard X-ray Observations Of M31mentioning

confidence: 99%

“…We classify these sources as non-magnetized neutron stars and find no optical counterpart, suggesting that they could be LMXBs because these types of stars would be too faint to be observed in the PHAT survey. Additionally, Stiele & Kong (2018) discuss several sources that are too hard to be located in the XRB area of their hardness ratio diagrams. One of these sources is in our sample (NuSTAR source 91) and is classified as a pulsar with no optical counterpart.…”

Section: Comparison With Other Hard X-ray Observations Of M31mentioning

confidence: 99%

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Young Accreting Compact Objects in M31: The Combined Power of NuSTAR, Chandra, and Hubble

Lazzarini

Hornschemeier

Williams

et al. 2018

ApJ

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We present 15 high mass X-ray binary (HMXB) candidates in the disk of M31 for which we are able to infer compact object type, spectral type of the donor star, and age using multiwavelength observations from NuSTAR, Chandra, and the Hubble Space Telescope (HST). The hard X-ray colors and luminosities from NuSTAR permit the tentative classification of accreting X-ray binary systems by compact object type, distinguishing black hole from neutron star systems. We find hard state black holes, pulsars, and non-magnetized neutron stars associated with optical point source counterparts with similar frequency. We also find nine non-magnetized neutron stars coincident with globular clusters and an equal number of pulsars with and without point source optical counterparts. We perform spectral energy distribution (SED) fitting for the most likely optical counterparts to the HMXB candidates, finding 7 likely high mass stars and 1 possible red Helium burning star. The remaining 7 HMXB optical counterparts have poor SED fits, so their companion stars remain unclassified. Using published star formation histories, we find that the majority of HMXB candidates -X-ray sources with UV-bright point source optical counterpart candidates -are found in regions with star formation bursts less than 50 Myr ago, with 3 associated with young stellar ages (<10 Myr). This is consistent with similar studies of HMXB populations in the Magellanic Clouds, M33, NGC 300, and NGC 2403.

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