Ersin Gögüs

Learn More
We study the temporal and coarse spectral properties of 268 bursts from SGR 1806−20 and 679 bursts from SGR 1900+14, all observed with the Rossi X-Ray Timing Explorer/Proportional Counter Array. Hardness ratios and temporal parameters, such as T90 durations and τ 90 emission times are determined for these bursts. We find a lognormal distribution of burst(More)
The Soft Gamma Repeater, SGR 1900+14, entered a new phase of activity in April 2001 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 RXTE orbits. This X-ray flux excess decayed over the next several minutes and was subsequently linked to a high(More)
We study the statistics of soft gamma repeater (SGR) bursts, using a data base of 187 events detected with BATSE and 837 events detected with RXTE PCA, all from SGR 1900+14 during its 1998-1999 active phase. We find that the fluence or energy distribution of bursts is consistent with a power law of index 1.66, over 4 orders of magnitude. This scale-free(More)
Soft gamma repeaters (SGRs) and anomalous x-ray pulsars form a rapidly increasing group of x-ray sources exhibiting sporadic emission of short bursts. They are believed to be magnetars, that is, neutron stars powered by extreme magnetic fields, B ~ 10(14) to 10(15) gauss. We report on a soft gamma repeater with low magnetic field, SGR 0418+5729, recently(More)
The ROTSE-IIIa telescope at Siding Spring Observatory, Australia, detected prompt optical emission from Swift GRB 050401. We present observations of the early optical afterglow, first detected by the ROTSE-IIIa telescope 33 s after the start of g-ray emission, contemporaneous with the brightest peak of this emission. This GRB was neither exceptionally long(More)
We investigated the development of astronomy and astrophysics research productivity in Turkey in terms of publication output and their impacts as reflected in the science citation index for the period 1980–2010. Our study involves 838 refereed publications, including 801 articles, 16 letters, 15 reviews, and six research notes. The number of papers were(More)
We present X-ray imaging, timing, and phase resolved spectroscopy of the anomalous X-ray pulsar 4U 0142+61 using the Chandra X-ray Observatory (CXO). The spectrum is well described by a power law plus blackbody model with Γ = 3.35(2), kTBB= 0.458(3) keV, and NH= 0.91(2) × 10 22 cm; we find no significant evidence for spectral features (0.5− 7.0 keV). Time(More)
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 long(More)
We present the results obtained by INTEGRAL on the Soft-Gamma Ray Repeater SGR 1806–20 . In particular we report on the temporal and spectral properties of the bursts detected during a moderately active period of the source in September and October 2003 and on the search for quiescent emission.
The intermediate polar (IP) RE 0751+14 (PQ Gem) was discovered with the Wide Field Camera of the ROSAT satellite (Mason et al., 1992). The detection of coherent 13.9 minute (or 833 sec) oscillations in the infrared and optical wavelengths are verified by hard X-ray observations of Ginga satellite. By using the optical spectroscopy and photometry Rosen et(More)