Discovery of X-ray bursts from Aquila X-1

Koyama, K.; Inoue, Hajime; Makishima, K.; Matsuoka, M.; Murakami, T.; Oda, M.; Osgawara, Y.; Ohashi, T.; Shibazaki, N.; Tanaka, Y.; Marshall, F. J.; Kondò, I.; Hayakawa, S.; Kunieda, H.; Makino, Fumiaki; Masai, K.; Nagase, F.; Tawara, Yuzuru; Miyamoto, S.; Tsunemi, H.; Yamashita, Koujun

doi:10.1086/183582

Cited by 57 publications

(46 citation statements)

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“…Aql X-1 is a transient LMXB that exhibits (normal) thermonuclear X-ray bursts and mHz QPOs (e.g., Koyama et al 1981; Revnivtsev et al 2001; Altamirano et al 2008). It is located at a distance of D≃5 kpc (e.g., Rutledge et al 2001), and spins at a frequency of νs≃550 Hz (as inferred from coherent X-ray pulsations detected once during a ≃150-s episode; Casella et al 2008).…”

Section: Aql X-1mentioning

confidence: 99%

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Waterhouse

Degenaar

Wijnands

et al. 2016

Mon. Not. R. Astron. Soc.

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Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as well as the short and faint 2015 outburst, to investigate the hypothesis that cooling of the accretion-heated neutron star crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that the X-ray light curves and measured neutron star surface temperatures are consistent with the expectations of the crust cooling paradigm. By using a thermal evolution code, we find that ≃1.2 − 3.2 MeV nucleon −1 of shallow heat release describes the observational data well, depending on the assumed mass-accretion rate and temperature of the stellar core. We find no evidence for varying strengths of this shallow heating after different outbursts, but this could be due to limitations of the data. We argue that monitoring Aql X-1 for up to ≃1 year after future outbursts can be a powerful tool to break model degeneracies and solve open questions about the magnitude, depth and origin of shallow heating in neutron star crusts.

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Section: Aql X-1mentioning

confidence: 99%

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Waterhouse

Degenaar

Wijnands

et al. 2016

Mon. Not. R. Astron. Soc.

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“…In transients like e.g. Aql X-1, Cen X-4, XTE J1709−267 and SAX J1750.8−2900, X-ray bursts were detected during the decline of the outburst, at times when the persistent flux, easily detectable at L x ∼ > 10 36 erg s −1 , was at an accretion rate of ordinary burst sources (Matsuoka et al 1980;Koyama et al 1981;Cocchi et al 1998;Natalucci et al 1999). Also the transient SAX J1808.4−3658 showed a ∼100 s long burst 30 days after the peak of an outburst, when the persistent flux had declined below the detection limit of the Wide Field Cameras, <10 36 erg s −1 (in 't ).…”

Section: Comparison With Burst Theorymentioning

confidence: 99%

BeppoSAX Wide Field Cameras observations of six type I X-ray bursters

Cornelisse

Verbunt

Zand

et al. 2002

A&A

108

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Abstract.We have discovered three certain (SAX J1324.5−6313, 2S 1711−339 and SAX J1828.5−1037) and two likely (SAX J1818.7+1424 and SAX J2224.9+5421) new thermonuclear X-ray burst sources with the BeppoSAX Wide Field Cameras, and observed a second burst ever from a sixth one (2S 0918−549). Four of them (excluding 2S 1711−339 and 2S 0918−549) are newly detected X-ray sources from which we observed single bursts, but no persistent emission. We observe the first 11 bursts ever from 2S 1711−339; persistent flux was detected during the first ten bursts, but not around the last burst. A single burst was recently detected from 2S 0918−549 by Jonker et al. (2001); we observe a second burst showing radius expansion, from which a distance of 4.2 kpc is derived. According to theory, bursts from very low flux levels should last ∼ > 100 s. Such is indeed the case for the last burst from 2S 1711−339, the single burst from SAX J1828.5−1037 and the two bursts from 2S 0918−549, but not for the bursts from SAX J1324.5−6313, SAX J1818.7+1424 and SAX J2224.9+5421. The bursts from the latter sources all last ∼20 s. We suggest that SAX J1324.5−6313, SAX J1818.7+1424, SAX J1828.5−1037 and SAX J2224.9+5421 are members of the recently proposed class of bursters with distinctively low persistent flux levels, and show that the galactic distribution of this class is compatible with that of the standard low-mass X-ray binaries.

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“…In this Letter, we investigate one of NICER's first X-ray burst observations: a bright burst from AqlX-1. This source exhibits frequent accretion outbursts during which X-ray bursts have been observed (Koyama et al 1981), and disk reflection has been detected in the persistent emission (King et al 2016;Ludlam et al 2017). After describing the NICER observations of AqlX-1 (Section 2), we perform a detailed analysis of the soft excess in the burst spectrum (Section 3).…”

Section: Introductionmentioning

confidence: 99%

NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

Keek

Arzoumanian

Bult

et al. 2018

ApJL

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Accretion disks around neutron stars regularly undergo sudden strong irradiation by Type-I X-ray bursts powered by unstable thermonuclear burning on the stellar surface. We investigate the impact on the disk during one of the first X-ray burst observations with the Neutron Star Interior Composition Explorer (NICER) on the International Space Station. The burst is seen from AqlX-1 during the hard spectral state. In addition to thermal emission from the neutron star, the burst spectrum exhibits an excess of soft X-ray photons below 1 keV, where NICER's sensitivity peaks. We interpret the excess as a combination of reprocessing by the strongly photoionized disk and enhancement of the pre-burst persistent flux, possibly due to Poynting-Robertson drag or coronal reprocessing. This is the first such detection for a short sub-Eddington burst. As these bursts are observed frequently, NICER will be able to study how X-ray bursts affect the disk and corona for a range of accreting neutron star systems and disk states.

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Discovery of X-ray bursts from Aquila X-1

Cited by 57 publications

References 0 publications

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

BeppoSAX Wide Field Cameras observations of six type I X-ray bursters

NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

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