A5046603134- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- SAS software applications and methods
- High-pressure geophysics and materials
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Particle Detector Development and Performance
- Astrophysics and Star Formation Studies
- Geophysics and Sensor Technology
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Earthquake Detection and Analysis
- Statistical and numerical algorithms
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Geological and Geophysical Studies
- earthquake and tectonic studies
- Radio Astronomy Observations and Technology
Sabancı Üniversitesi
2015-2024
Tsinghua University
2016
University of Geneva
2016
Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata
2016
Swiss Institute of Comparative Law
2016
Institut d'Estudis Espacials de Catalunya
2014
Institute for Space Astrophysics and Planetology
2014
Osservatorio Astronomico di Cagliari
2011
University of Padua
2011
Centre National de la Recherche Scientifique
2011
Soft gamma repeaters and anomalous x-ray pulsars form a rapidly increasing group of sources exhibiting sporadic emission short bursts. They are believed to be magnetars, i.e. neutron stars powered by extreme magnetic fields, B~10^{14}-10^{15} Gauss. We report on soft repeater with low field, SGR 0418+5729, recently detected after it emitted bursts similar those magnetars. X-ray observations show that its dipolar field cannot greater than 7.5x10^{12} Gauss, well in the range ordinary radio...
We present multiwavelength observations of the afterglow GRB 130427A, brightest (in total fluence) gamma-ray burst (GRB) past 29 yr. Optical spectroscopy from Gemini-North reveals redshift to be z = 0.340, indicating that its unprecedented brightness is primarily result relatively close proximity Earth; intrinsic luminosities both and are not extreme in comparison other bright GRBs. a large suite spanning 300 s 130 days after demonstrate shows simple, smooth evolution at all frequencies,...
We report on the long term X-ray monitoring with Swift, RXTE, Suzaku, Chandra and XMM-Newton of outburst newly discovered magnetar Swift J1822.3-1606 (SGR 1822-1606), from first observations soon after detection short bursts which led to its discovery, through stages decay (covering time-span July 2011, until end April 2012). also archival ROSAT witnessed source during likely quiescent state, upper limits J1822.3-1606's radio-pulsed optical emission outburst, Green Bank Telescope (GBT) Gran...
We report on NICER observations of the Magnetar SGR~1935+2154, covering its 2020 burst storm and long-term persistent emission evolution up to $\sim90$ days post outburst. During first 1120~seconds taken April 28 00:40:58 UTC we detect over 217 bursts, corresponding a rate $>0.2$ bursts s$^{-1}$. Three hours later is at 0.008 s$^{-1}$, remaining comparatively low level thereafter. The $T_{90}$ duration distribution peaks 840~ms; waiting times next fit with log-normal an average 2.1 s. 1-10...
The megajansky radio burst, FRB 20200428, and other bright bursts detected from the Galactic source SGR J1935+2154 suggest that magnetars can make fast (FRBs), but emission site mechanism of FRB-like are still unidentified. Here, we report emergence a pulsar phase magnetar 5 months after 20200428. Pulses were in 16.5 hours over 13 days using Five-hundred-meter Aperture Spherical Telescope, with luminosities about eight decades fainter than pulses emitted narrow window anti-aligned x-ray...
We study the statistics of soft gamma repeater (SGR) bursts, using a data base 187 events detected with BATSE and 837 RXTE PCA, all from SGR 1900+14 during its 1998-1999 active phase. find that fluence or energy distribution bursts is consistent power law index 1.66, over 4 orders magnitude. This scale-free resembles Gutenberg-Richter Law for earthquakes, gives evidence self-organized criticality in SGRs. The time intervals between successive log-normal distribution. There no correlation...
On 2004 December 27, a highly-energetic giant flare was recorded from the magnetar candidate SGR 1806-20. In months preceding this flare, persistent X-ray emission object began to undergo significant changes. Here, we report on evolution of key spectral and temporal parameters prior following flare. Using Rossi Timing Explorer, track pulse frequency 1806-20 find that spin-down rate varied erratically in before after Contrary 1900+14, no evidence for discrete jump spin at time 27th (|dnu/nu|...
Starting in 2013 February, Swift has been performing short daily monitoring observations of the G2 gas cloud near Sgr A* with X-Ray Telescope to determine whether interaction leads an increase flux from Galactic center. On April 24 detected order magnitude rise X-ray region A*. Initially thought be a flare A*, detection hard burst same by Burst Alert suggested that was unresolved new Soft Gamma Repeater, SGR J1745−29. Here we present discovery J1745−29 Swift, including analysis data before,...
We report on a complete set of early optical afterglows gamma-ray bursts (GRBs) obtained with the Robotic Optical Transient Search Experiment (ROTSE-III) telescope network from 2005 March through 2007 June. This is comprised 12 and Swift/X-Ray Telescope observations, median ROTSE-III response time 45 s after start γ-ray emission (8 GCN notice time). These span 4 orders magnitude in luminosity, contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding flares,...
We report on the long-term X-ray monitoring of outburst decay low magnetic field magnetar SGR 0418+5729 using all available data obtained with RXTE, Swift, Chandra, and XMM-Newton observations from discovery source in 2009 June up to 2012 August. The timing analysis allowed us obtain first measurement period derivative 0418+5729: s s−1, significant at a ∼3.5σ confidence level. This leads surface dipolar Bdip ≃ 6 × 1012 G. confirms as lowest magnetar. Following flux spectral evolution...
Aql X--1 is one of the most prolific low mass X-ray binary transients (LMXBTs) showing outbursts almost annually. We present results our spectral analyses RXTE/PCA observations 2000 and 2011 outbursts. investigate changes related to changing disk-magnetosphere interaction modes X--1. The light curves LMXBTs typically show phases fast rise exponential decay. decay phase shows a "knee" where flux goes from slow rapid stage. assume that corresponds weak propeller stage at which fraction...
We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in January 2009, resulting largest uniform sample properties bursts. used combination broadband high time-resolution data provided GBM to perform statistical studies for source properties. determine durations, emission times, duty cycles rise times all bursts, find that they are typical explore various models our analysis, conclude...
Abstract We analyzed broadband X-ray and radio data of the magnetar SGR J1935+2154 taken in aftermath its 2014, 2015, 2016 outbursts. The source soft spectrum <10 keV is well described with a blackbody+power-law (BB+PL) or 2BB model during all three Nuclear Spectroscopic Telescope Array observations revealed hard tail, PL photon index Γ = 0.9, extending up to 50 keV, flux comparable one detected keV. Imaging analysis Chandra did not reveal small-scale extended emission around source....
Some short GRBs are followed by longer extended emission, lasting anywhere from ~10 to ~100 s. These with emission (EE) can possess observational characteristics of both and long (as represented GRB 060614), the traditional classification based on observed duration places some them in class. While EE pose a challenge compact binary merger scenario, they may therefore provide an important link between events. To identify population regardless their initial classifications, we performed...
Abstract We present timing and time-integrated spectral analysis of 127 bursts from SGR J1935+2154. These were observed with the Gamma-ray Burst Monitor on Fermi Space Telescope Alert Neil Gehrels Swift Observatory during source’s four active episodes 2014 to 2016. This activation frequency makes J1935+2154 most burst prolific transient magnetar. find average duration all detected be much shorter than typical, anticipated value. fit spectra two blackbody functions, a Comptonized model three...
Abstract We present temporal and time-integrated spectral analyses of 148 bursts from the latest activation SGR J1935+2154, observed with Fermi/Gamma-ray Burst Monitor 2019 October 4 through 2020 May 20, excluding an ∼130 s segment a very high burst density on April 27. The presented here are slightly longer softer than earlier activations as well other magnetars. long-term evolution trend is interpreted being associated increase in average plasma loading magnetosphere during bursts. also...
We report the detection of large flux changes in persistent X-ray soft gamma repeater (SGR) 1900+14 during its burst active episode 1998. Most notably, we find a factor ~700 increase nonburst following August 27 flare, which decayed time as power law. Our measurements indicate that pulse fraction remains constant throughout this decay. This suggests global enhancement consequence flare rather than localized heating. While has since recovered to preoutburst level, profile not. The shape...
On 2009 June 5, the Gamma-ray Burst Monitor (GBM) onboard Fermi Space Telescope triggered on two short, and relatively dim bursts with spectral properties similar to Soft Gamma Repeater (SGR) bursts. Independent localizations of by triangulation Konus-RF Swift satellite, confirmed their origin from same, previously unknown, source. The subsequent discovery X-ray pulsations Rossi Timing Explorer (RXTE), magnetar nature new source, SGR J0418+5729. We describe here Fermi/GBM observations,...
Some supernovae (SNe) show evidence for mass-loss events taking place prior to their explosions. Measuring pre-outburst rates provide essential information regarding the mechanisms that are responsible these events. Here we present XMM-Newton and Swift X-ray observations taken after latest, presumably final, outburst of SN 2009ip. We use as well new near infra-red visible light spectra, published radio put six independent order-of-magnitude constrains on rate progenitor explosion. Our...
The discovery of quasi-periodic oscillations (QPOs) in magnetar giant flares has opened up prospects for neutron star asteroseismology. scarcity makes a search QPOs the shorter, far more numerous bursts from Soft Gamma Repeaters (SGRs) desirable. In Huppenkothen et al (2013), we developed Bayesian method searching short bursts, taking into account effects complicated burst structure, and have shown its feasibility on small sample bursts. Here, apply same to much larger storm 286 SGR...
ABSTRACT We report on the analysis of two deep XMM-Newton observations magnetar Swift J1834.9−0846 and its surrounding extended emission taken in 2014 March October, 2.5 3.1 yr after source went into outburst. The is only weakly detected first observation, with an absorption-corrected flux <?CDATA ${F}_{0.5-10\mathrm{keV}}\approx 4\times {10}^{-14}$?> erg s −1 cm −2 a $3\sigma $?> upper limit during second observation about 3 × 10 −14 . This level more than orders magnitude lower measured at...
We present statistics of SGR 1806-20 bursts, combining 290 events detected with the Rossi X-Ray Timing Explorer/Proportional Counter Array, 111 Burst and Transient Source Experiment, 134 International Cometary Explorer. find that fluence distribution bursts observed each instrument are well described by power laws indices 1.43, 1.76, 1.67, respectively. The time intervals between successive from is a lognormal function peak at 103 s. There no correlation burst intensity either waiting times...
We have monitored the pulse frequencies of two soft gamma repeaters SGR 1806-20 and 1900+14 through beginning year 2001 using primarily Rossi X-Ray Timing Explorer Proportional Counter Array observations. In both sources, we observe large changes in spin-down torque up to a factor ~4, which persist for several months. Using long-baseline phase-connected timing solutions as well overall frequency histories, construct noise power spectra each SGR. The spectrum source is very red (power-law...