The 2008 May burst activation of SGR 1627–41 Esposito, P.; Israel, G. L.; Zane, S. ...
Monthly notices of the Royal Astronomical Society. Letters,
October 2008, Letnik:
390, Številka:
1
Journal Article
Recenzirano
Odprti dostop
In 2008 May, the soft gamma-ray repeater (SGR) SGR 1627–41 resumed its bursting activity after nearly a decade of quiescence. After detection of a bright burst, Swift pointed its X-ray telescope in ...the direction of the source in less than five hours and followed it for over five weeks. In this Letter, we present an analysis of the data from these Swift observations and an XMM–Newton one performed when SGR 1627–41 was still in a quiescent state. The analysis of the bursts detected with Swift/Burst Alert Telescope shows that their temporal and spectral properties are similar to those found in previous observations of SGR 1627–41 and other SGRs. The maximum peak luminosity of the bursts was ∼2 × 1041 erg s−1. Our data show that the outburst was accompanied by a fast flux enhancement and by a hardening of the spectrum with respect to the persistent emission.
GRB 050911, discovered by the Swift Burst Alert Telescope, was not seen 4.6 hr later by the Swift X-ray Telescope, making it one of the very few X-ray nondetections of a gamma-ray burst (GRB) ...afterglow at early times. The g-ray light curve shows at least three peaks, the first two of which (6T sub(0)-0.8 and T sub(0) + 0.2 s, where T sub(0) is the trigger time) were short, each lasting 0.5 s. This was followed by later emission 10-20 s postburst. The upper limit on the unabsorbed X-ray flux was 1.7 x 10 super(-14) ergs cm super(-2) s super(-1) (integrating 46 ks of data taken between September 11 and 18), indicating that the decay must have been rapid. All but one of the long bursts detected by Swift were above this limit at 64.6 hr, whereas the afterglows of short bursts became undetectable more rapidly. Deep observations with Gemini also revealed no optical afterglow 12 hr after the burst, down to r = 24.0 (5 s limit). We speculate that GRB 050911 may have been formed through a compact object (black hole-neutron star) merger, with the later outbursts due to a longer disk lifetime linked to a large mass ratio between the merging objects. Alternatively, the burst may have occurred in a low-density environment, leading to a weak, or nonexistent, forward shock - the so-called "naked GRB" model.
ABSTRACT Gamma-ray bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae are generally characterized by non-relativistic ejecta. GRB afterglows decelerate rapidly, usually ...within days, because their low-mass ejecta rapidly sweep up a comparatively larger mass of circumstellar material. However, supernovae with heavy ejecta can be in nearly free expansion for centuries. Supernovae were thought to have non-relativistic outflows except for a few relativistic ones accompanied by GRBs. This clear division was blurred by SN 2009bb, the first supernova with a relativistic outflow without an observed GRB. However, the ejecta from SN 2009bb was baryon loaded and in nearly free expansion for a year, unlike GRBs. We report the first supernova discovered without a GRB but with rapidly decelerating mildly relativistic ejecta, SN 2012ap. We discovered a bright and rapidly evolving radio counterpart driven by the circumstellar interaction of the relativistic ejecta. However, we did not find any coincident GRB with an isotropic fluence of more than one-sixth of the fluence from GRB 980425. This shows for the first time that central engines in SNe Ic, even without an observed GRB, can produce both relativistic and rapidly decelerating outflows like GRBs.
Swift and optical observations of GRB 050401 De Pasquale, Massimiliano; Beardmore, Andy P.; Barthelmy, S. D. ...
Monthly notices of the Royal Astronomical Society,
January 2006, Letnik:
365, Številka:
3
Journal Article
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We present the results of the analysis of γ-ray and X-ray data of GRB 050401 taken with the Swift satellite, together with a series of ground-based follow-up optical observations. The Swift X-ray ...light curve shows a clear break at about 4900 s after the γ-ray burst (GRB). The decay indices before and after the break are consistent with a scenario of continuous injection of radiation from the ‘central engine’ of the GRB to the fireball. Alternatively, this behaviour could result if ejecta are released with a range of Lorentz factors, with the slower shells catching up the faster at the afterglow shock position. The two scenarios are observationally indistinguishable. The GRB 050401 afterglow is quite bright in the X-ray band, but weak in the optical, with an optical to X-ray flux ratio similar to those of ‘dark bursts’. We detect a significant amount of absorption in the X-ray spectrum, with NH= (1.7 ± 0.2) × 1022cm−2 at a redshift of z= 2.9, which is typical of a dense circumburst medium. Such high column density implies an unrealistic optical extinction of 30 mag if we adopt a Galactic extinction law, which would not be consistent with the optical detection of the afterglow. This suggests that the extinction law is different from the Galactic one.
Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) displaying X-ray outbursts that can reach peak luminosities up to 10
38
erg s
−1
and spend most of their lives in more ...quiescent states with luminosities as low as 10
32
−10
33
erg s
−1
. During the quiescent states, less luminous flares are also frequently observed with luminosities of 10
34
−10
35
erg s
−1
. The main goal of the comprehensive and uniform analysis of the SFXT
Swift
triggers presented in this paper is to provide tools to predict whether a transient that has no known X-ray counterpart may be an SFXT candidate. These tools can be exploited for the development of future missions exploring the variable X-ray sky through large field-of-view instruments. We examined all available data on outbursts of SFXTs that triggered the
Swift
/Burst Alert Telescope (BAT) collected between 2005 August 30 and 2014 December 31, in particular those for which broad-band data, including the
Swift
/X-ray Telescope (XRT) data, are also available. This work complements and extends our previous catalogue of SFXT flares detected by BAT from 2005 February 12 to 2013 May 31, since we now include the additional BAT triggers recorded until the end of 2014 (i.e. beyond the formal first 100 months of the
Swift
mission). Due to a change in the mission’s observational strategy, virtually no SFXT triggers obtained a broad-band response after 2014. We processed all BAT and XRT data uniformly by using the
Swift
Burst Analyser to produce spectral evolution dependent flux light curves for each outburst in the sample. The BAT data allowed us to infer useful diagnostics to set SFXT triggers apart from the general
γ
-ray burst population, showing that SFXTs uniquely give rise to image triggers and are simultaneously very long, faint, and ‘soft’ hard-X-ray transients. We find that the BAT data alone can discriminate very well the SFXTs from other classes of fast transients, such as anomalous X-ray pulsars and soft gamma repeaters. On the contrary, the XRT data collected around the time of the BAT triggers are shown to be decisive for distinguishing SFXTs from, for instance, accreting millisecond X-ray pulsars and jetted tidal disruption events. The XRT observations of 35 (out of 52 in total) SFXT BAT triggers show that in the soft X-ray energy band, SFXTs display a decay in flux from the peak of the outburst of at least three orders of magnitude within a day and rarely undergo large re-brightening episodes, favouring in most cases a rapid decay down to the quiescent level within three to five days (at most).
On 2010 March 19, the Swift/Burst Alert Telescope triggered on a short burst with temporal and spectral characteristics similar to those of soft gamma repeater (SGR) bursts. The source location, ...however, did not coincide with any known SGR. Subsequent observations of the source error box with the Swift/X-Ray Telescope and the Rossi X-ray Timing Explorer led to the discovery of a new X-ray source with a spin period of 7.56 s, confirming SGR J1833-0832 as a new magnetar. Based on our detailed temporal and spectral analyses, we show that the new SGR is rapidly spinning down (4 x 10{sup -12} s s{sup -1}) and find an inferred dipole magnetic field of 1.8 x 10{sup 14} G. We also show that the X-ray flux of SGR J1833-0832 remained constant for approximately 20 days following the burst and then started to decline. We derived an accurate location of the source with the Chandra X-ray Observatory and we searched for a counterpart in deep optical and infrared observations of SGR J1833-0832, and for radio pulsed emission with the Westerbork Radio Synthesis Telescope. Finally, we compare the spectral and temporal properties of the source to other magnetar candidates.
We investigate the environment of the nearby (d 40 Mpc) broad-lined Type Ic supernova (SN) 2009bb. This event was observed to produce a relativistic outflow likely powered by a central accreting ...compact object. While such a phenomenon was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB was detected in association with SN 2009bb. Using an optical spectrum of the SN 2009bb explosion site, we determine a variety of interstellar medium properties for the host environment, including metallicity, young stellar population age, and star formation rate. We compare the SN explosion site properties to observations of LGRB and broad-lined SN Ic host environments on optical emission line ratio diagnostic diagrams. Based on these analyses, we find that the SN 2009bb explosion site has a metallicity between 1.7 Z and 3.5 Z, in agreement with other broad-lined SN Ic host environments and at odds with the low-redshift LGRB host environments and recently proposed maximum metallicity limits for relativistic explosions. We consider the implications of these findings and the impact that SN 2009bb's unusual explosive properties and environment have on our understanding of the key physical ingredient that enables some SNe to produce a relativistic outflow.
Abstract
We present the catalog of InterPlanetary Network (IPN) localizations for 199 short-duration gamma-ray bursts (sGRBs) detected by the Konus-Wind (KW) experiment between 2011 January 1 and ...2021 August 31, which extends the initial sample of IPN-localized KW sGRBs to 495 events. We present the most comprehensive IPN localization data on these events, including probability sky maps in Hierarchical Equal Area isoLatitude Pixelization format.
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