Statistical Properties of SGR 1900+14 Bursts

Göǧüş, E.; Woods, Peter; Kouveliotou, C.; Paradijs, J. van; Briggs,; Duncan, Robert C.; Thompson, Christopher

doi:10.1086/312380

Cited by 150 publications

(115 citation statements)

References 26 publications

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“…The waiting time distribution can be fit by a wide lognormal distribution with a mean T waiting = 34 ± 11 s and a scatter of 2.3 s < T waiting < 496 s. At the peak of activity, the waiting time between subsequent bursts decreases to a time scale comparable to the duration of individual spikes, so that the bursts can be considered as either separate events or as parts of the "multispike" flares. This behavior is similar to the one observed in SGR bursts (Gögüş et al 1999). At the same time, the observed scatter of the waiting times is larger than the one found in the RXTE observations of 1E 2259+586 by Gavriil et al (2004), who found that the waiting time between subsequent bursts is always larger than 1 s (≥10 times longer than the typical burst duration).…”

Section: Statistical Study Of the Burst Propertiessupporting

confidence: 86%

“…The observed fluence-duration correlation is different from the one observed in 1E 2259+586 (F ∼ T 0.54±0.08 by Gavriil et al 2004) and instead resembles more the fluence-duration relation of SGR bursts, e.g. F ∼ T 1.13 in SGR 1900+14, (Gögüş et al 1999) (note that the correlation F − T correlation is not very tight both in our case and in the case of SGR 1900+14, so that the two relations are consistent).…”

Section: Statistical Study Of the Burst Propertiescontrasting

confidence: 80%

“…The bursting activity appears to be a random process with a waiting time between the bursts distributed lognormally and with no correlation between the waiting time and the burst intensity (Hurley et al 1994). The burst intensities follow a power law distribution (Gögüş et al 1999). Similar bursting activity is observed also in AXPs (Gavriil et al 2002;Kaspi et al 2003;Gavriil et al 2004Gavriil et al , 2008Woods et al 2005;Israel et al 2007).…”

Section: Introductionsupporting

confidence: 67%

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SGR-like flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408

Savchenko¹,

Neronov²,

Beckmann³

et al. 2010

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Aims. We studied an exceptional period of activity of the anomalous X-ray pulsar 1E 1547.0-5408 in January 2009, during which about 200 hard X-ray / soft γ-ray bursts were detected by different instruments on board of ESA's γ-ray observatory INTEGRAL. Methods. The major activity episode (22 January 2009), which was detected by NASA's γ-ray telescope Swift, happened when the source was outside the field of view of all the INTEGRAL instruments. But we were still able to study the statistical properties as well as spectral and timing characteristics of 84 short (100 ms−10 s) bursts from the source during this activity period detected simultaneously by the anti-coincidence shield of the spectrometer SPI on board of INTEGRAL and by the detector of the imager IBIS/ISGRI. Results. We find that the luminosity of the 22 January 2009 bursts of 1E 1547.0-5408 was ≥10 42 erg s −1 above ∼80 keV. This luminosity is comparable to that of the bursts of soft gamma repeaters (SGR) and is at least two orders of magnitude larger than the luminosity of the previously reported bursts from AXPs. Similarly to the SGR bursts, the brightest bursts of 1E 1547.0-5408 consist of a short spike of ∼100 ms duration with a hard spectrum, followed by a softer extended tail of 1-10 s duration, which occasionally exhibits pulsations with the source spin period of ∼2 s. The "short spike + tail" template is not valid for all the observed bursts. We also observe a certain amount of ∼1 s duration bursts either without a spike or with a spike delayed with respect to the onset of the burst. A third type of bursts is the "flat-top" burst of sub-second duration, which is similar to the "precursors" observed in the SGR flares. We find that the bursts of 1E 1547.0-5408 harden with increasing luminosity. Such a behavior is opposite of those observed in SGR bursts, but is similar to the hardness-luminosity relation observed in AXP 1E 2259+586. We confirm the existence of a correlation between the burst fluences and durations and the absence of a correlation between the burst fluence and the waiting time between subsequent bursts, previously established for the AXP 1E 2259+586. Conclusions. The observation of AXP bursts with luminosities comparable to the one of SGR bursts strengthens the conjecture that AXPs and SGRs are different representatives of one and the same source type, and that the AXP and SGR bursts are triggered by a similar type of instabilities.

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Section: Statistical Study Of the Burst Propertiessupporting

confidence: 86%

Section: Statistical Study Of the Burst Propertiescontrasting

confidence: 80%

Section: Introductionsupporting

confidence: 67%

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SGR-like flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408

Savchenko¹,

Neronov²,

Beckmann³

et al. 2010

A&A

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“…Interestingly, soft γ-ray repeaters also have a power-law energy frequency distribution 25,26 with α E ∼ 1.5. A power-law distribution of occurrence frequency is characteristic of a SOC system 20 .…”

Section: Lines Inmentioning

confidence: 99%

Self-organized criticality in X-ray flares of gamma-ray-burst afterglows

2013

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X-ray flares detected in nearly half of gamma-ray-burst (GRB) afterglows are one of the most intriguing phenomena in highenergy astrophysics 1-8 . All of the observations indicate that the central engines of bursts, after the gamma-ray emission has ended, still have long periods of activity, during which energetic explosions eject relativistic materials, leading to late-time X-ray emission 2,9,10 . It is thus expected that X-ray flares provide important clues as to the nature of the central engines of GRBs, and more importantly, unveil the physical mechanism of the flares themselves, which has so far remained mysterious. Here we report statistical results of X-ray flares of GRBs with known redshifts, and show that X-ray flares and solar flares share three statistical properties: power-law frequency distributions for energies, durations and waiting times. All of the distributions can be well understood within the physical framework of a self-organized criticality (SOC) system. The statistical properties of X-ray flares of GRBs are similar to solar flares, and thus both can be attributed to a SOC process. Both types of flares may be driven by a magnetic reconnection process, but X-ray flares of GRBs are produced in ultra-strongly magnetized millisecond pulsars 11,12 or long-term hyperaccreting disks around stellar-mass black holes 13 .GRBs are flashes of gamma-rays occurring at cosmological distances with an isotropic-equivalent energy release from 10 51 to 10 54 ergs 9,10,14,15 . They can be sorted into two classes: shortduration hard-spectrum bursts (< 2 s) and long-duration softspectrum bursts 16 . Thanks to the rapid-response capability and high sensitivity of the Swift satellite 17 , numerous unforeseen features have been discovered, one of which is that about half of the bursts have large, late-time X-ray flares with short rise and decay times 4,5 . Unexpected X-ray flares with an isotropicequivalent energy from 10 48 to 10 52 ergs have been detected for both long and short bursts 4,6,7 . The occurrence times of X-ray flares range from a few seconds to 10 6 seconds after the GRB trigger 8 . Until now, the physical mechanism of X-ray flares has remained mysterious, although some models have been proposed 9,10 . Due to the 8-year observations of Swift, plentiful X-ray flare data have been collected. Here we investigate the frequency distributions of energies, durations and waiting times of GRB X-ray flares for the first time. On the other hand, it is well known that solar flares with a timescale of hours are explosive phenomena in the solar atmosphere with an energy release of about 10 28 -10 32 ergs, which are widely believed to be triggered by a magnetic reconnection process 18 . They have been observed in broadband electromagnetic waves, but we focus here on solar hard X-ray flares.Although X-ray flares are common phenomena in GRBs and the Sun, the flare energy spans about 20 orders of magnitude and an outstanding question appears, namely, do GRB X-ray flares and solar flares have a similar physical mechani...

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“…The importance of ITDs cannot be overstated, as is the case for other different astrophysical sources, such as the Sun (e.g., Wheatland 2000;Aschwanden & McTiernan 2010), and outbursting magnetars (Göǧüş et al 1999(Göǧüş et al , 2000Gavriil et al 2004). In the case of GRBs a number of papers have investigated this property (McBreen et al 1994;Norris et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Gamma-ray burst engines may have no memory

Baldeschi

Guidorzi

2014

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Context. A sizeable fraction of gamma-ray burst (GRB) time profiles consist of a temporal sequence of pulses. The nature of this stochastic process carries information on how GRB inner engines work. The so-called interpulse time defines the interval between adjacent pulses, excluding the long quiescence periods during which the signal drops to the background level. It was found by many authors in the past that interpulse times are lognormally distributed, at variance with the exponential case that is expected for a memoryless process. Aims. We investigated whether the simple hypothesis of a temporally uncorrelated sequence of pulses is really to be rejected, as a lognormal distribution necessarily implies. Methods. We selected and analysed a number of multi-peaked CGRO/BATSE GRBs and simulated similar time profiles, with the crucial difference that we assumed exponentially distributed interpulse times, as is expected for a memoryless stationary Poisson process. We then identified peaks in both data sets using a novel peak search algorithm, which is more efficient than others used in the past. Results. We independently confirmed that the observed interpulse time distribution is approximately lognormal. However, we found the same results on the simulated profiles, in spite of the intrinsic exponential distribution. Although intrinsic lognormality cannot be ruled out, this shows that intrinsic interpulse time distribution in real data could still be exponential, while the observed lognormal could be ascribed to the low efficiency of peak search algorithms at short values combined with the limitations of a bin-integrated profile. Conclusions. Our result suggests that GRB engines may emit pulses after the fashion of nuclear radioactive decay, that is, as a memoryless process.

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Statistical Properties of SGR 1900+14 Bursts

Cited by 150 publications

References 26 publications

SGR-like flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408

SGR-like flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408

Self-organized criticality in X-ray flares of gamma-ray-burst afterglows

Gamma-ray burst engines may have no memory

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