The Smooth Cyclotron Line in Her X-1 as Seen With Nuclear Spectroscopic Telescope Array

Fürst, Felix; Grefenstette, Brian W.; Staubert, R.; Tomsick, John A.; Bachetti, Matteo; Barret, D.; Bellm, Eric C.; Boggs, Steven E.; Chenevez, J.; Christensen, Finn Erland; Craig, William W.; Hailey, Charles J.; Harrison, Fiona A.; Klochkov, D.; Madsen, Kristin K.; Pottschmidt, K.; Stern, Daniel; Walton, D. J.; Wilms, J.

doi:10.1088/0004-637x/779/1/69

Cited by 66 publications

(96 citation statements)

References 48 publications

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“…Her X−1 displays an intensity and spectral variability with an on/off cycle of 35 d. The X-ray emission from Her X−1 is well described by a power law with similar photon index as observed in 3X J0043 (below 10 keV); a soft excess, which can be described by a blackbody with temperature kT ∼ 130-140 eV, is also present, and is likely associated with the accretion disk (e.g. Burderi et al 2000;Fürst et al 2013). Although Her X−1 shows a lower X-ray luminosity than 3X J0043, reaching only ∼10 37 erg s −1 , its spectral and timing properties (hard power law below 10 keV, e.g.…”

Section: Discussionmentioning

confidence: 73%

EXTraS discovery of an 1.2-s X-ray pulsar in M 31

Esposito

Israel

Belfiore

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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During a search for coherent signals in the X-ray archival data of XMM-Newton, we discovered a modulation at 1.2 s in 3XMM J004301.4+413017 (3X J0043), a source lying in the direction of an external arm of M 31. This short period indicates a neutron star (NS). Between 2000 and 2013, the position of 3X J0043 was imaged by public XMM-Newton observations 35 times. The analysis of these data allowed us to detect an orbital modulation at 1.27 d and study the long-term properties of the source. The emission of the pulsar was rather hard (most spectra are described by a power law with < 1) and, assuming the distance to M 31, the 0.3-10 keV luminosity was variable, from ∼3 × 10 37 to 2 × 10 38 erg s −1 . The analysis of optical data shows that, while 3X J0043 is likely associated to a globular cluster in M 31, a counterpart with V 22 outside the cluster cannot be excluded. Considering our findings, there are two main viable scenarios for 3X J0043: a peculiar low-mass X-ray binary, similar to 4U 1822−37 or 4U 1626−67, or an intermediate-mass X-ray binary resembling Her X−1. Regardless of the exact nature of the system, 3X J0043 is the first accreting NS in M 31 in which the spin period has been detected.Key words: galaxies: individual: M 31 -X-rays: binaries -X-rays: individual: 3XMM J004301.4+413017. I N T RO D U C T I O NEXTraS (Exploring the X-ray Transient and variable Sky) is a project to explore systematically the serendipitous content of the XMM-Newton European Photon Imaging Camera (EPIC) pn (Strüder et al. 2001) and MOS (Turner et al. 2001) data in the temporal domain. The results will be released to the astronomical community in an easy-to-use form. The project includes a search for fast transients missed by standard image analysis, as well as the search and characterization of variability (both periodical and aperiodical) in hundreds of thousands of sources, spanning more than nine orders of magnitude in time-scale (from <1 s to >10 yr) and

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Section: Discussionmentioning

confidence: 73%

EXTraS discovery of an 1.2-s X-ray pulsar in M 31

Esposito

Israel

Belfiore

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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“…The X-ray broadband (0.5-50 keV) spectral properties, i.e., the hard spectrum ( 1 G~) at lower energies with a cutoff around 15-20 keV, are more consistent with Galactic X-ray pulsars (e.g., Hung et al 2010;Camero-Arranz et al 2012;Fürst et al 2013) than with BH binaries and neutron star binaries with weak magnetic fields (Z-sources and atoll sources). Our observations suggest that there is a soft X-ray excess in this system, and the soft excess has also been seen in several accreting pulsars (e.g., Nagase 2002; Hickox et al 2004).…”

Section: Discussionmentioning

confidence: 84%

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Yukita

Ptak

Hornschemeier

et al. 2017

ApJ

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We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E<10 keV observations did not generate much attention. This source has a spectrum with a soft X-ray excess (kT ∼ 0.2 keV) plus a hard spectrum with a power law of 1 G~and a cutoff around 15-20 keV, typical of the spectral characteristics of accreting pulsars. Unfortunately, any potential pulsation was undetected in the NuSTAR data, possibly due to insufficient photon statistics. The existing deep HST images exclude high-mass (>3 M  ) donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass (<3 M  ) companion or a symbiotic X-ray binary. We discuss other possibilities in more detail.

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“…Using the same response and background files, and adopting the same exposure times as the real data, we simulated 10,000 sets of XMM-Newton (pn and combined MOS1+MOS2) and NuSTAR (FPMA and FPMB) spectra with the FAKEIT command in XSPEC based on the best-3 We have also tried replacing the CUTOFFPL model with the FD-CUT and NPEX models also frequently applied to Galactic neutron stars (e.g. Odaka et al 2013;Fürst et al 2013;Islam et al 2015;Vybornov et al 2017), but these provide identical fits to the CUTOFFPL model, so we do not present the results in full.…”

Section: Time-averaged Spectroscopymentioning

confidence: 99%

Super-Eddington accretion on to the neutron star NGC 7793 P13: Broad-band X-ray spectroscopy and ultraluminous X-ray sources

Walton

Fürst

Harrison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a detailed, broadband X-ray spectral analysis of the ULX pulsar NGC 7793 P13, a known super-Eddington source, utilizing data from the XMM-Newton, NuSTAR and Chandra observatories. The broadband XMM-Newton+NuSTAR spectrum of P13 is qualitatively similar to the rest of the ULX sample with broadband coverage, suggesting that additional ULXs in the known population may host neutron star accretors. Through time-averaged, phaseresolved and multi-epoch studies, we find that two non-pulsed thermal blackbody components with temperatures ∼0.5 and 1.5 keV are required to fit the data below 10 keV, in addition to a third continuum component which extends to higher energies and is associated with the pulsed emission from the accretion column. The characteristic radii of the thermal components appear to be comparable, and are too large to be associated with the neutron star itself, so the need for two components likely indicates the accretion flow outside the magnetosphere is complex. We suggest a scenario in which the thick inner disc expected for super-Eddington accretion begins to form, but is terminated by the neutron star's magnetic field soon after its onset, implying a limit of B 6 × 10 12 G for the dipolar component of the central neutron star's magnetic field. Evidence of similar termination of the disc in other sources may offer a further means of identifying additional neutron star ULXs. Finally, we examine the spectrum exhibited by P13 during one of its unusual 'off' states. These data require both a hard powerlaw component, suggesting residual accretion onto the neutron star, and emission from a thermal plasma, which we argue is likely associated with the P13 system.

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The Smooth Cyclotron Line in Her X-1 as Seen With Nuclear Spectroscopic Telescope Array

Cited by 66 publications

References 48 publications

EXTraS discovery of an 1.2-s X-ray pulsar in M 31

EXTraS discovery of an 1.2-s X-ray pulsar in M 31

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Super-Eddington accretion on to the neutron star NGC 7793 P13: Broad-band X-ray spectroscopy and ultraluminous X-ray sources

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