Kevin Hurley's research while affiliated with University of California, Berkeley and other places
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Publications (219)
Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the universe. The duration and hardness distribution of GRBs has two clusters, now understood to reflect (at least) two different progenitors. Short-hard GRBs (SGRBs; T₉₀ <2 s) arise from compact binary mergers, while long-soft GRBs (LGRBs; T₉₀ >2 s) have been attributed t...
Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the universe. The duration and hardness distribution of GRBs has two clusters, now understood to reflect (at least) two different progenitors. Short-hard GRBs (SGRBs; T90 <2 s) arise from compact binary mergers, while long-soft GRBs (LGRBs; T90 >2 s) have been attributed t...
![Figure 4: Typical WAM spectra for 6 bright GRBs[42]](publication/337418554/figure/fig4/AS:827660016025605@1574340933874/Typical-WAM-spectra-for-6-bright-GRBs42_Q320.jpg)
We have systematically studied the spectral properties of 302 localized gamma-ray bursts (GRBs) observed by the Suzaku wide-band all-sky monitor (WAM) from 2005 August to 2010 December. The energy spectra in the 100–5000 keV range integrated over the entire emission and the 1 s peak were fitted by three models: a single power law, a power law with...
We will review results for gamma-ray bursts (GRBs) and soft gamma repeaters (SGRs), obtained from the Suzaku Wide-band All-sky Monitor (WAM) which operated for about 10 years from 2005 to 2015. The WAM is a BGO (bismuth germanate: Bi 4 Ge 3 O 12) lateral shield for the Hard X-ray Detector (HXD), used mainly for rejecting its detector background, bu...
We report on the T90 and T50 duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed
by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly
bimodal in three energy ranges (50–120, 120–250, and 250–550 keV), but is un...
The Fermi Gamma-Ray Space Telescope has greatly expanded the number and
energy window of observations of gamma-ray bursts (GRBs). However, the coarse
localizations of tens to a hundred square degrees provided by the Fermi
Gamma-ray Burst Monitor (GBM) instrument have posed a formidable obstacle to
locating the bursts' host galaxies, measuring their...
The first gravitational-wave (GW) observations will greatly benefit from the detection of coincident electromagnetic counterparts.
Electromagnetic follow-ups will nevertheless be challenging for GWs with poorly reconstructed directions. GW source localization
can be inefficient (i) if only two GW observatories are in operation; (ii) if the detector...
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...
Jet heating via nuclear collisions may be the main mechanism for gamma-ray
burst (GRB) emission. Besides producing the observed gamma-rays, collisional
heating must generate 10-100 GeV neutrinos, implying a close relation between
the neutrino and gamma-ray luminosities. We exploit this theoretical relation
to make predictions for possible GRB detec...
We present the results of a search for gravitational waves associated with 154 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments in 2009-2010, during the sixth LIGO science run and the second and third Virgo science runs. We perform two distinct searches: a modeled search for coalescences of either two neutron star...
We present the results of a search for gravitational waves associated with
154 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray
experiments in 2009-2010, during the sixth LIGO science run and the second and
third Virgo science runs. We perform two distinct searches: a modeled search
for coalescences of either two neutron star...
Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitation...
The observational properties of the soft gamma repeaters are reviewed briefly, starting with the time histories and energy spectra of their bursts. The short bursts and giant flares are compared. Their quiescent emission is presented, and the context of the magnetar model is discussed.
Spectral studies of bursts from SGR0501+4516 are presented using Suzaku data. We discovered hard X-ray emission in a summed spectrum of short bursts with low fluences, which has been found only
in quiescent emission spectra so far. This result supports our idea that there are common emission mechanisms between the
quiescent emission and the bursts...
We review the notion that some extragalactic giant magnetar flares could be mistaken for short cosmic gamma-ray bursts. There are at least two general ways to approach this problem. One is statistical, while the other considers individual bursts. Both methods appear to agree that extragalactic flares can be, and indeed are, present in the short bur...
Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to
be magnetars: neutron stars powered by extreme magnetic fields. These rare
objects are characterized by repeated and sometimes spectacular gamma-ray
bursts. The burst mechanism might involve crustal fractures and excitation of
non-radial modes which would emit gravitation...
Using a pulse-fit method, we investigated the spectral lags between the traditional gamma-ray band (50-400 keV) and the X-ray band (6-25keV) for 8 GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, GRB 021211, GRB 030528, GRB 040924, GRB 041006, and GRB 050408), detected with the WXM and FREGATE instruments aboard the HETE-2 satellite....
The BGO anticoincidence shield of the Suzaku Hard X-Ray
Detector Wideband All-Sky Monitor (HXD WAM) has been designed to act as a gamma-ray burst
detector. It was incorporated into the 3rd interplanetary network shortly after launch, and it is now detecting about one confirmed gamma-ray or soft gamma repeater burst every 2.5 days. It has detected a...
The data of the nine spacecraft Interplanetary Network are being used to refine GBM localizations of gamma-ray bursts. This effort is 1) assisting the GBM team to understand and reduce systematic uncertainties, 2) reducing the sizes of GBM and LAT localizations by one to four orders of magnitude, 3) facilitating the identification of GRB sources wi...
The interplanetary network (IPN) now comprises 9 spacecraft with a total of 11 distinct experi-ments: AGILE (2 experiments), Fermi (GBM), RHESSI, Suzaku, and Swift, in low Earth orbit; INTEGRAL, in an eccentric orbit with apogee 0.5 light-seconds; Konus-Wind, at distances up to 7 light-seconds from Earth; MESSENGER, on its way to Mercury; and Mars...
The anticoincidence system of the INTEGRAL spectrometer has been an essential component of the interplanetary network since launch. It has observed about 600 events which have been confirmed as either soft gamma repeaters or cosmic gamma ray bursts by other instruments in the IPN. It has also observed over 130 events which are unconfirmed, but whic...
We report here on the outburst onset and evolution of the new soft gamma-ray repeater SGR 0501+4516. We monitored the new SGR with XMM–Newton starting on 2008 August 23, 1 day after the source became burst active, and continuing with four more observations in the following month, with the last one on 2008 September 30. Combining the data with the S...
The Suzaku Wide‐band All‐sky Monitor (WAM) consists of 20 BGO anti‐coincidence scintillators for the Hard X‐ray Detector (HXD). The WAM has a wide field of view (FOV), about half of the whole sky, a large collecting area, 800 cm2, and broad‐band energy coverage from 50 to 5000 keV. Thus it has been designed to work as a gamma‐ray burst detector. Fo...
We report an study of the accuracy of GBM GRB localizations, analyzing three types of localizations: those produced automatically by the GBM Flight Software on board GBM, those produced automatically with ground software in near real time, and localizations produced with human guidance. The two types of automatic locations are distributed in near r...
Time-resolved spectroscopy may help to determine the still unknown emission mechanism which produces prompt gamma-ray burst spectra. Prompt spectra evolve significantly over timescales much shorter than the total burst duration. It has been proposed that this evolution is due to the presence of thermal components which are masked in time-integrated...
We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exce...
The history and observational properties of the soft gamma repeaters are reviewed in this Chapter. Over the past decades, we have gone from viewing these objects as a special class of cosmic gamma-ray burst, to seeing them as one manifestation of magnetars. There is now a solid body of multiwavelength observations, as well as some more controversia...
We present the results of deep infrared imaging in J, H, and K of the quiescent X-ray source located within the 1992 May 1 gamma-ray burst error box. The field is crowded, containing both stars and galaxies, and we discuss the likelihood that they are associated with the X-ray source. Two objects (one star and one galaxy) appear to be the most inte...
Empirical probability models for BATSE gamma-ray burst (GRB) location errors are developed via a Bayesian analysis of the separations between BATSE GRB locations and locations obtained with the Interplanetary Network (IPN). Models are compared and their parameters estimated using 392 GRBs with single IPN annuli and 19 GRBs with intersecting IPN ann...
The All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE) has been used to localize 13 confirmed X-ray counterparts to gamma-ray bursts (GRBs) detected over 3 yr of operation. We quantify the errors in ASM localizations of brief transient sources by using observations of persistent sources with well-known locations. We apply the results o...
The Suzaku Wide-band All-sky Monitor (WAM) consists of thick BGO
anti-coincidence shields of the Hard X-ray Detectors (HXD). It views
about half of the sky and has a geometrical area of 800cm2
per side and an effective area of 400cm2, even at 1MeV.
Hence, the WAM can provide unique opportunities to detect high-energy
emission from GRBs and solar fl...
We report the discovery of soft (0.25-2 keV) X-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (greater than 10 keV) H, O, and S ions from the region of the IPT seems to be the likely source of the X-ray emission from the Galilean satellites. According to our e...
![FIG. 1.ÈA 10A ] 10A portion of the HST STIS clear-aperture CCD image of...](profile/Larry-Petro/publication/231109013/figure/fig1/AS:339949397266436@1458061660472/EA-10A-10A-portion-of-the-HST-STIS-clear-aperture-CCD-image-of-the-Deld-of-GRB-000301C_Q320.jpg)
We present Space Telescope Imaging Spectrograph observations of the optical transient (OT) counterpart of the γ-ray burster GRB 000301C obtained 5 days after the burst, on 2000 March 6. CCD clear-aperture imaging reveals a R 21.50 ± 0.15 source with no apparent host galaxy. An 8000 s, 1150 Å < λ < 3300 Å near-ultraviolet MAMA prism spectrum shows a...
We have monitored the pulse frequencies of the two soft gamma repeaters SGR 1806-20 and SGR 1900+14 through the beginning of year 2001 using primarily Rossi X-Ray Timing Explorer Proportional Counter Array observations. In both sources, we observe large changes in the spin-down torque up to a factor of ~4, which persist for several months. Using lo...
We present evidence for burst emission from SGR 1900+14 with a power-law high-energy spectrum extending beyond 500 keV. Unlike previous detections of high-energy photons during bursts from soft gamma repeaters (SGRs), these emissions are not associated with extraordinarily bright flares. Not only is the emission hard, but the spectra are better fit...
The soft gamma repeater SGR 1900+14 entered a new phase of activity in 2001 April initiated by the intermediate flare recorded on April 18. Ten days following this flare, we discovered an abrupt increase in the source flux between consecutive Rossi X-Ray Timing Explorer (RXTE) orbits. This X-ray flux excess decayed over the next several minutes and...
We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X- Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of ≈4), and is detectable in earlier RXTE observations back...
We present the results from a Hubble Space Telescope ACS search for supernovae associated with X-ray flashes 020903, 040701, 040812, and 040916. We find strong evidence that XRF 020903 (z = 0.25) was associated with a SN 1998bw-like supernova and confirm this using optical spectroscopy at t ~ 25 days. We find no evidence, however, for SN 1998bw-lik...
We report the detection of large flux changes in the persistent X-ray flux of soft gamma repeater (SGR) 1900+14 during its burst active episode in 1998. Most notably, we find a factor of ~700 increase in the nonburst X-ray flux following the August 27 flare, which decayed in time as a power law. Our measurements indicate that the pulse fraction rem...
We have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observations of the pulsed emission from SGR 1900+14 during 1996 September, 1998 June-October, and early 1999. Using these measurements and results reported elsewhere, we construct a period history of this source for 2.5 yr. We find significant deviations from a steady spin-dow...
We present Keck/NIRSPEC near-IR images and Magellan/IMACS optical spectroscopy of the host galaxy of GRB 031203. The host is an actively star-forming galaxy at z = 0.1055 ± 0.0001. This is the lowest redshift GRB to date, aside from GRB 980425. From the hydrogen Balmer lines, we infer an extinction of AV = 3.62 ± 0.25 or a total reddening ET(B - V)...
We present precise localizations of AXP 1E1841-045 and SGR 1627-41 with Chandra. We obtained new infrared observations of SGR 1627-41 and reanalyzed archival observations of AXP 1E1841-045 in order to refine their positions and search for infrared counterparts. A faint source is detected inside the error circle of AXP 1E1841-045. In the case of SGR...
The long, bright gamma-ray burst GRB 070125 was localized by the Interplanetary Network. We present light curves of the prompt gamma-ray emission as observed by Konus-Wind, RHESSI, Suzaku WAM, and Swift BAT. We detail the results of joint spectral fits with Konus and RHESSI data. The burst shows moderate hard-to-soft evolution in its multipeaked em...
Since the discovery of the cosmological origin of gamma-ray bursts (GRBs), there has been growing interest in using these transient events to probe the quantum gravity energy scale in the range 1016-1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a measurable modification in the electromagnetic radiation dispers...
We report the discovery of a new soft gamma repeater (SGR), SGR 1627-41, and present BATSE observations of the burst emission and BeppoSAX Narrow-Field Instrument observations of the probable persistent X-ray counterpart to this SGR. All but one burst spectrum are well fit by an optically thin thermal bremsstrahlung model with kT values between 25...
The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 deg2 or better produced no detections. The earliest limiting sensitivity is mROTSE > 13.1 at 10.85 s (5 s exposure) after...
Gamma-ray bursts of short duration may harbor vital clues to the range of phenomena producing bursts. However, recent progress from the observation of optical counterparts has not benefited the study of short bursts. We have searched for early optical emission from six gamma-ray bursts using the telephoto array on the Robotic Optical Transient Sear...
We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant fla...
We present the results of a LIGO search for short-duration gravitational waves (GW) associated with soft gamma repeater (SGR) bursts. This is the first GW search sensitive to neutron star f-modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 2004 Dece...
We present the results of a LIGO search for short-duration gravitational waves (GWs) associated with Soft Gamma Repeater (SGR) bursts. This is the first search sensitive to neutron star f-modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 200...
We analyzed the available LIGO data coincident with GRB 070201, a short-duration, hard-spectrum γ-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral arms of the Andromeda galaxy (M31). Possible progenitors of such short, hard GRBs include mergers of neutron stars or a neutron star and a black hole, or so...
A follow-up ToO observation of the burst active SGR 1627-41 (GCN #7777, ATEL #1548) with Chandra was carried out on 2008 June 3. The on-source exposure time for this observation was 40 ks during which the ACIS detectors recorded ~1100 counts from the SGR in CC mode.
We report on multi-wavelength observations, ranging from the X-ray to radio wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic observations reveal the presence of absorption lines due to O I, Si II, and C IV, implying a likely redshift of z = 1.547. The well-sampled light curves, in particular from 0.5 to 4 days after the bu...
A long and extremely soft X-ray flash was detected and localized by the
instruments aboard the HETE-2 at 00:03:30 UT on 2004 Sep. 16. This burst
consists of two peaks separated by ~200 s, with durations of about 110 s
and 60 s. We have analyzed the energy spectra of the 1st and 2nd peaks
observed with the Wide Field X-Ray Monitor (WXM) and the Fren...
An understanding of the origin of the short gamma-ray bursts remains an elusive and exciting pursuit. A great leap forward has been made over the past three years with the first rapid localizations and afterglow detections of such events, but follow-up has yet to reveal a detailed understanding of the progenitors and the nature of the afterglow lig...
We have performed a joint analysis of prompt emission from four bright short gamma-ray bursts (GRBs) with the Suzaku-WAM and the Konus-Wind experiments. This joint analysis allows us to investigate the spectral properties of short-duration bursts over a wider energy band with a higher accuracy. We find that these bursts have a high |$E_{\rm peak}$|...
GRB041006 was detected by HETE-2 on 2004 October 06. The light curves in four different energy bands display different features.
At higher energy bands several peaks are seen in the light curve, while at lower energy bands a single broader bump dominates.
It is expected that these different features are the result of a mixture of several components...
One of the challenges of the Swift era has been accurately determining Epeak for the prompt GRB emission. RHESSI, which is sensitive from 30 keV to 17 MeV, can extend spectral coverage above the Swift-BAT bandpass. Using the public Swift data, we present results of joint spectral fits for 26 bursts co-observed by RHESSI and Swift-BAT through May 20...
High Energy Neutron Detector HEND operates more than 7 years onboard NASA`s Mars Odyssey. More than 150 cosmic gamma-ray bursts and soft gamma-ray repeaters were detected during the long period of space operations, which have often used for bursts localization program "The Third Interplanetary Network". This instrument is capable to perform continu...
The history and observational properties of the soft gamma repeaters are reviewed. Over the past decades, we have gone from viewing these objects as a special class of cos-mic gamma-ray burst, to seeing them as one manifestation of magnetars. There is now a solid body of multi-wavelength observations, as well as some more controversial properties....
We present the study of a complete sample containing all the gamma-ray
bursts (GRBs) localized by the WXM on-board the satellite HETE-2. All
the 82 bursts defining our sample are selected with uniform criteria
which are fully understood, can be reproduced, and are common for all
the events (e.g. angle of incident beam, detection threshold,
signal-t...
We describe a systematic search, still in progress, for gamma-ray bursts associated with optically identified energetic supernovae. The results (negative so far) can be explained in various ways. It is possible that not all energetic Type Ic supernovae produce gamma-ray bursts. If they do, though, our non-detections can be explained by beaming, sof...
Since the discovery of the cosmological origin of GRBs there has been growing interest in using these transient events to probe the Quantum Gravity energy scale in the range 1016–1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a modification in the electromagnetic radiation dispersion relation, specifically, an...
Temporal and spectral studies of short bursts ($\lesssim$ a few hundred milliseconds) are presented for the soft gamma repeaters (SGRs) 1806$-$20 and 1900$+$14 using the HETE-2 samples. In five years from 2001 to 2005, HETE-2 localized 50 bursts from SGR1806$-$20 and 5 bursts from SGR 1900 $+$14. The cumulative number–intensity distribution of SGR...
Temporal and spectral studies of short bursts (≲ a few hundred
milliseconds) are presented for the soft gamma repeaters (SGRs) 1806-20
and 1900+14 using the HETE-2 samples. In five years from 2001 to 2005,
HETE-2 localized 50 bursts from SGR1806-20 and 5 bursts from SGR1900+14.
The cumulative number-intensity distribution of SGR1806-20 in the activ...
Thanks to INTEGRAL’s long exposures of the Galactic Plane, the two brightest Soft Gamma-Ray Repeaters, SGR 1806-20 and SGR 1900+14, have been monitored and studied in detail for the first time at hard-X/soft gamma rays.
This has produced a wealth of new scientific results, which we will review here. Since SGR 1806-20 was particularly active during...
While long gamma-ray bursts (GRBs) have been conclusively demonstrated over the past ten years to be distributed at great cosmological distances, the nature of short duration (
A long X-ray flash was detected and localized by the instruments aboard the
High Energy Transient Explorer II (HETE-2) at 00:03:30 UT on 2004 September 16.
The position was reported to the GRB Coordinates Network (GCN) approximately 2
hours after the burst. This burst consists of two peaks separated by 200 s,
with durations of 110 s and 60 s. We ha...