Time resolved spectroscopy of SGR J1550−5418 bursts detected with Fermi/gamma-ray burst monitor

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dc.citation.firstpage52en_US
dc.citation.journalTitleThe Astrophysical Journalen_US
dc.citation.lastpage63en_US
dc.citation.volumeNumber785en_US
dc.contributor.authorYounes, G.en_US
dc.contributor.authorKouveliotou, C.en_US
dc.contributor.authorvan der Horst, A.J.en_US
dc.contributor.authorBaring, M.G.en_US
dc.contributor.authorGranot, J.en_US
dc.contributor.authorWatts, A.L.en_US
dc.contributor.authorBhat, P.N.en_US
dc.contributor.authorCollazzi, A.en_US
dc.contributor.authorGehrels, N.en_US
dc.contributor.authorGorgone, N.en_US
dc.contributor.authorGogus, E.en_US
dc.contributor.authorGruber, D.en_US
dc.contributor.authorGrunblatt, S.en_US
dc.contributor.authorHuppenkothen, D.en_US
dc.contributor.authorKaneko, Y.en_US
dc.contributor.authorvon Kienlin, A.en_US
dc.contributor.authorvan der Klis, M.en_US
dc.contributor.authorLin, L.en_US
dc.contributor.authorMcenery, J.en_US
dc.contributor.authorvan Putten, T.en_US
dc.contributor.authorWijers, R.A.M.J.en_US
dc.date.accessioned2014-04-14T20:56:34Zen_US
dc.date.available2014-04-14T20:56:34Zen_US
dc.date.issued2014en_US
dc.description.abstractWe report on a time-resolved spectroscopy of the 63 brightest bursts of SGR J1550–5418, detected with the Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms timescales to characterize the spectral evolution of the bursts. Using a Comptonized model, we find that the peak energy, E peak, anti-correlates with flux, while the low-energy photon index remains constant at ~ – 0.8 up to a flux limit F ≈ 10–5 erg s–1 cm–2. Above this flux value, the E peak–flux correlation changes sign, and the index positively correlates with the flux reaching ~1 at the highest fluxes. Using a two blackbody model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time the evolution of the temperatures and areas as a function of flux. We find that the area–kT relation follows the lines of constant luminosity at the lowest fluxes, R 2vpropkT –4, with a break at the higher fluxes (F > 10–5.5 erg s–1 cm–2). The area of the high-kT component increases with the flux while its temperature decreases, which we interpret as being due to an adiabatic cooling process. The area of the low-kT component, on the other hand, appears to saturate at the highest fluxes, toward R max ≈ 30 km. Assuming that crust quakes are responsible for soft gamma repeater (SGR) bursts and considering R max as the maximum radius of the emitting photon-pair plasma fireball, we relate this saturation radius to a minimum excitation radius of the magnetosphere, and we put a lower limit on the internal magnetic field of SGR J1550–5418, B int gsim 4.5 × 1015 G.en_US
dc.identifier.citationYounes, G., Kouveliotou, C., van der Horst, A.J., et al.. "Time resolved spectroscopy of SGR J1550−5418 bursts detected with Fermi/gamma-ray burst monitor." <i>The Astrophysical Journal,</i> 785, (2014) The American Astronomical Society: 52-63. http://dx.doi.org/10.1088/0004-637X/785/1/52.en_US
dc.identifier.doihttp://dx.doi.org/10.1088/0004-637X/785/1/52en_US
dc.identifier.urihttps://hdl.handle.net/1911/75890en_US
dc.language.isoengen_US
dc.publisherThe American Astronomical Societyen_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.titleTime resolved spectroscopy of SGR J1550−5418 bursts detected with Fermi/gamma-ray burst monitoren_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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