Peter Bult, Giulio C. Mancuso, Tod E. Strohmayer, Arianna C. Albayati, Diego Altamirano, Douglas J. K. Buisson, Jérôme Chenevez, Sebastien Guillot, Tolga Güver,… 展开作者
Peter Bult, Giulio C. Mancuso, Tod E. Strohmayer, Arianna C. Albayati, Diego Altamirano, Douglas J. K. Buisson, Jérôme Chenevez, Sebastien Guillot, Tolga Güver, Wataru Iwakiri, Gaurava K. Jaisawal, Mason Ng, Andrea Sanna, Jean H. Swank
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13 pages, 6 figures, 2 tables. Accepted for publication in ApJ
We present observations of the historic transient 4U 1730-22 as observed with the Neutron Star Interior Composition Explorer (NICER). After remaining in quiescence since its 1972 discovery, this X-ray binary showed renewed outburst activity in 2021 and 2022. We observed 4U 1730-22 extensively with NICER, detecting a total of 17 thermonuclear X-ray bursts. From a spectroscopic analysis, we find that these X-ray bursts can be divided into a group of bright and weak bursts. All bright bursts showed $1\sim2$ second rise times and a photospheric radius expansion phase, while the weak bursts showed a slower $\sim5$ second rise with a tendency for concave shapes. From the photospheric radius expansion flux, we estimate the source distance at $6.9\pm0.2$ kpc. We consider various interpretations for our observations and suggest that they may be explained if accreted material is burning stably at the stellar equator, and unstable ignition occurs at a range of higher latitudes.
We report the temporal and spectral analysis of three thermonuclear X-ray bursts from 4U 1608-52, observed by the Neutron Star Interior Composition Explorer (NICER) during and just after the outburst observed from the source in 2020. In two of the X-ray bursts, we detect secondary peaks, 30 and 18 seconds after the initial peaks. The secondary peaks show a fast rise exponential decay-like shape resembling a thermonuclear X-ray burst. Time-resolved X-ray spectral analysis reveals that the peak flux, blackbody temperature, and apparent emitting radius values of the initial peaks are in agreement…
We report results obtained from the study of 12 thermonuclear X-ray bursts in 6 AstroSat observations of a neutron star X-ray binary and well-known X-ray burster, 4U 1636$-$536. Burst oscillations at $\sim$581 Hz are observed with 4$-$5$σ$ confidence in three of these X-ray bursts. The rising phase burst oscillations show a decreasing trend of the fractional rms amplitude at 3$σ$ confidence,by far the strongest evidence of thermonuclear flame spreading observed with AstroSat. During the initial 0.25 second of the rise a very high value (34.0$\pm$6.7%) is observed. The concave shape of the frac…
Thermonuclear (type-I) bursts arise from unstable ignition of accumulated fuel on the surface of neutron stars in low-mass X-ray binaries. Measurements of burst properties in principle enable observers to infer the properties of the host neutron star and mass donors, but a number of confounding astrophysical effects contribute to systematic uncertainties. Here we describe some commonly-used approaches for determining system parameters, including composition of the burst fuel, and introduce a new suite of software tools, concord, intended to fully account for astrophysical uncertainties. Compar…
The millisecond pulsar MAXI J1816-195 was recently discovered in an outburst by MAXI in 2022 May. We study different properties of the pulsar using data from NuSTAR and NICER observations. The unstable burning of accreted material on the surface of neutron stars induces thermonuclear (Type-I) bursts. Several such thermonuclear bursts have been detected by MAXI J1816-195 during its outburst. We investigate the evolution of the burst profile with flux and energy using NuSTAR and NICER observations. During the NuSTAR observation, a total of four bursts were detected from the source. The duration …
Broadband spectral studies of Type-I X-ray bursts can put strong constraints on the physics of burst spectra as well as their interaction with the environment. We present the results obtained from the broadband time-resolved spectroscopy of 15 thermonuclear bursts detected simultaneously from the neutron star atoll source 4U 1636-536 using LAXPC and SXT onboard AstroSat. During the observations with AstroSat, the Low mass X-ray binary (LMXB) 4U 1636-536 is observed to show a modest spectral evolution within the island state. The broadband burst spectra are observed to show an excess in additio…
We report results from the spectro-timing analysis of the atoll source 4U 1636$-$536 observed with NuSTAR and AstroSat during its hard spectral state. In three observations of 207 ks total exposure, we identify 31 thermonuclear X-ray bursts including five doublets and a triplet. Recurrence time as short as 3.8 minutes is seen in one of the doublets. To the best of our knowledge, this is the shortest recurrence time known for this source. Our time-averaged spectroscopy during the bursts indicate the presence of an additional powerlaw or a blackbody component in a few cases, perhaps due to varyi…
We measured the thermonuclear burning efficiency as a function of accretion rate for the Type I X-ray bursts of five low-mass X-ray binary systems. We chose sources with measured neutron star spins and a substantial population of bursts from a large observational sample. The general trend for the burst rate is qualitatively the same for all sources; the burst rate first increases with the accretion rate up to a maximum, above which the burst rate declines, despite the increasing accretion rate. At higher accretion rates, when the burst rate decreases, the α-value (the ratio of accretion energy…
X-ray Reflection and An Exceptionally Long Thermonuclear Helium Burst from IGR J17062-6143
来自吸积中子星的热核X射线爆发对周围环境的短暂但强烈的辐射，为研究吸积物理提供了一种独特的方法。我们分析了2015年IGR J17062-6143观测到的一天闪光的MAXI/GSC和Swift/XRT光谱。这是一个罕见的在0.15%爱丁顿低吸积光度下重复爆发的例子。从2015年爆发和2012年前一次爆发之间拍摄的MAXI，Chandra和NuSTAR观测的光谱被用来确定吸积柱。我们发现它与5x10^10 g cm^-2的爆发点火柱一致，这表明它很可能是由在深氦层中燃烧提供动力的。观测到的爆发通量超过一天，并按照直接的幂律衰减：F~t^-1.15。爆发和持久的光谱很好地描述了从中子星的热辐射，康普顿化的这种发射在一个热的光学薄介质周围的恒星，和光电离的吸积盘的反射。在爆发峰值处，康普顿化分量消失，此时爆发可以耗散康普顿化气体，并且它在爆发尾部返回。反射信号表明，内盘在爆发前被截断在约100个引力半径处，但在爆发期间可能会向恒星靠近。在爆发结束时，通量下降到低于爆发冷却趋势2天，然后返回到爆发前水平。
We report the detection of 5 Type-1 thermonuclear X-ray bursts and one burst-like event in the neutron star LMXB source, Cyg X-2 using X-ray data obtained with the Large Area X-ray Proportional Counter (LAXPC) instrument on board AstroSat. We carry out an energy resolved burst profile analysis as well as time resolved spectral analysis for each of the bursts and characterize their properties. All bursts are weak with burst peak-to-persistent intensity ratios $<$ 3, decay times $\sim$2 s, and with fluences $\sim$1$\times$10$^{-8}$ ergs/cm$^2$, indicating that the observed bursts are Helium fuel…
Accreting millisecond X-ray pulsars (AMXPs) show burst oscillations during thermonuclear explosions of the accreted plasma which are markedly different from those observed in non-pulsating low mass X-ray binaries. The AMXP XTE J1814-338 is known for having burst oscillations that are phase locked (constant phase difference) and coincident with the accretion powered pulsations during all its thermonuclear bursts but the last one. In this work we use a coherent timing analysis to investigate this phenomenon in more detail and with higher time resolution than was done in the past. We confirm that…
We report the results of an observation of low mass X-ray binary GX 3+1 with {\it AstroSat}'s Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope (SXT) instruments on-board for the first time. We have detected one Type-1 thermonuclear burst ($\sim$ 15 s) present in the LAXPC 20 light curve, with a double peak feature at higher energies and our study of the hardness-intensity diagram reveals that the source was in a soft banana state. The pre-burst emission could be described well by a thermally Comptonised model component. The burst spectra is modelled adopting a time-resolv…
We present spectral and temporal properties of all the thermonuclear X-ray bursts observed from Aql X-1 by the Neutron Star Interior and Composition Explorer (NICER) between 2017 July and 2021 April. This is the first systematic investigation of a large sample of type I X-ray bursts from Aql X-1 with improved sensitivity at low energies. We detect 22 X-ray bursts including two short recurrence burst events in which the separation was only 451 s and 496 s. We perform time resolved spectroscopy of the bursts using the fixed and scaled background (f_a method) approaches. We show that the use of a…
