Andere Organsysteme

Götz, M.

doi:10.1007/978-3-642-56796-4_12

Cited by 5 publications

(8 citation statements)

References 114 publications

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“…Figure 3 shows the relationship between lower and higher temperatures (kT LT and kT HT ). The 2BB temperatures were obtained by our study and previous works (Morii et al 2003;Feroci et al 2004;Olive et al 2004;Gotthelf et al 2004;Tiengo et al 2005;Götz et al 2006a;Mereghetti et al 2006a;Nakagawa et al 2007). The 2BB temperatures of 51 short bursts detected by HETE-2 are also plotted in figure 3 ).…”

Section: Spectral Parameter Of Two Blackbody Functionsupporting

confidence: 78%

Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

Nakagawa

Yoshida

Yamaoka

et al. 2009

Publications of the Astronomical Society of Japan

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Spectral studies of quiescent emission and bursts of magnetar candidates using XMM-Newton, Chandra and Swift data are presented. Spectra of both the quiescent emission and the bursts for most magnetar candidates are reproduced by a photoelectrically absorbed two blackbody function (2BB). There is a strong correlation between lower and higher temperatures of 2BB (kT LT and kT HT ) for the magnetar candidates of which the spectra are well reproduced by 2BB. In addition, a square of radius for kT LT (R 2 LT ) is well correlated with a square of radius for kT HT (R 2 HT ). A ratio kT LT /kT HT ≈ 0.4 is nearly constant irrespective of objects and/or emission types (i.e., the quiescent emission and the bursts). This would imply a common emission mechanism among the magnetar candidates. The relation between the quiescent emission and the bursts might be analogous to a relation between microflares and solar flares of the sun. Three AXPs (4U 0142+614, 1RXS J170849.0−400910 and 1E 2259+586) seem to have an excess above ∼ 7 keV which well agrees with a non-thermal hard component discovered by INTEGRAL.

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Section: Spectral Parameter Of Two Blackbody Functionsupporting

confidence: 78%

Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

Nakagawa

Yoshida

Yamaoka

et al. 2009

Publications of the Astronomical Society of Japan

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“…The spectral evolution observed in these events is not in common with SGR 1806-20 or SGR 1900+14 (Aptekar et al 2001), but resembles the SGR 1627-41 bursts, where a strong hardness-intensity correlation was noticed in the Konus-Wind observations (Mazets et al 1999). In contrast, a hardness-intensity anti-correlation was found in some weak short bursts as well as throughout the overall burst sample from SGR 1806-20 observed with INTEGRAL (Götz et al 2004(Götz et al , 2006. Among 55 bursts from SGR 1806-20 and SGR 1900+14 observed by HETE-2 only for 3 bursts was a clear (but moderate) hardness-intensity anti-correlation reported; for the other 3 bursts, a hint of a hard component at end of the burst was found (Nakagawa et al 2007).…”

Section: Discussionmentioning

confidence: 61%

“…The SGR bursts fluences tend to follow a power law distribution (Gögüş et al 2000;Aptekar et al 2001;Götz et al 2006). However, the exact shape and parameters of the observed fluences and peak fluxes distributions are not well determined, and may be subject to a detection-specific bias.…”

Section: Discussionmentioning

confidence: 99%

Konus-Wind Observations of the New Soft Gamma-Ray Repeater SGR 0501+4516

Aptekar

Cline

Frederiks

et al. 2009

ApJ

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In 2008 August, the new soft gamma-ray repeater SGR 0501+4516 was discovered by Swift. The source was soon confirmed by several groups in space-and ground-based multi-wavelength observations. In this letter we report the analysis of five short bursts from the recently discovered SGR, detected with Konus-Wind gamma-ray burst spectrometer. Properties of the time histories of the observed events, as well as results of multi-channel spectral analysis, both in the 20-300 keV energy range, show, that the source exhibits itself as a typical SGR. The bursts durations are 0.75 s and their spectra above 20 keV can be fitted by optically-thin thermal bremsstrahlung (OTTB) model with kT OT T B of 20-40 keV. The spectral evolution is observed, which resembles the SGR 1627-41 bursts, where a strong hardness-intensity correlation was noticed in the earlier Konus-Wind observations. The peak energy fluxes of all five events are comparable to highest those for known SGRs, so a less distant source is implied, consistent with the determined Galactic anti-center direction. Supposing the young supernova remnant HB9 (at the distance of 1.5 kpc) as a natal environment of the source, the peak luminosities of the bursts are estimated to be (2-5)×10 40 erg s −1 . The values of the total energy release, given the same assumptions, amount to (0.6-6)×10 39 erg. These estimations of both parameters are typical for short SGR bursts.

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“…4) is subject to errors through the SN rate estimate, and to Poisson error in the number of active SGRs in the Galaxy (4 +6 −3 ; 95% CL); The distance to SGR 1806−20 may be smaller than 15 kpc (e.g., 12kpc, Figer et al 2004;6-10 kpc, Cameron et al 2005), and therefore shifting the dark-gray zone (i.e., energy of the 2004 December 27 giant flare) in Fig. 9 to the left; Moreover, the value of the power-law index α may be different from 5/3 (e.g., Götz et al 2006; α = 1.9), and the luminosity function model is an approximation. In reality the energy distribution (i.e., dN/dE ∝ E −5/3 ) is probably not terminated abruptly at E max , as different SGRs may be born with different magnetic fields.…”

Section: The Rate Of Giant Flaresmentioning

confidence: 99%

Soft Gamma‐Ray Repeaters in Nearby Galaxies: Rate, Luminosity Function, and Fraction among Short Gamma‐Ray Bursts

Ofek

2007

ApJ

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It was suggested that some of the short-duration Gamma-Ray Bursts (GRB) are giant flares of Soft Gammaray Repeaters (SGR) in nearby galaxies. To test this hypothesis, I have constructed a sample of 47 short GRBs, detected by the Inter-Planetary Network (IPN), for which the position is constrained by at least one annulus on the celestial sphere. For each burst, I have checked whether its IPN 3-σ error region coincides with the apparent disk of one of 316 bright, star-forming galaxies found within 20 Mpc. I find a single match of GRB 000420B with M74, which could, however, be due to a chance coincidence. I estimate the IPN efficiency as a function of fluence and derive the galaxy sample completeness. I find that assuming there is a cut-off in the observed energy distribution of SGR flares at ≤ 10 47 erg, the fraction of SGRs among short GRBs with fluence above ∼ 10 −5 erg cm −2 is < 16% (< 27%) at the 95% (99.73%) confidence level. I estimate the number of active SGRs in each one of the galaxies in the sample, and combine it with the distances to these galaxies, the IPN efficiency, and the SGR flare energy distribution (Cheng et al.), to derive the rate of giant flares with energy above 4 × 10 46 erg. I find that the rate of such giant flares is about (0.4 − 5) × 10 −4 yr −1 per SGR. This rate is marginally consistent with the observed Galactic rate, of a single giant flare with energy above 4 × 10 46 erg in 30 years. Comparison of the Galactic rate with the inferred extragalactic rate implies a gradual cut-off (or steepening) of the flare energy distribution at 3 × 10 46 erg (95% confidence). Using the Galactic SGR flare rate, I set a lower limit of one percent on the fraction of SGR flares among short GRBs.

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Andere Organsysteme

Cited by 5 publications

References 114 publications

Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

Konus-Wind Observations of the New Soft Gamma-Ray Repeater SGR 0501+4516

Soft Gamma‐Ray Repeaters in Nearby Galaxies: Rate, Luminosity Function, and Fraction among Short Gamma‐Ray Bursts

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