Optical variabilities in Be/X-ray binary system:GRO J2058+42

We present an analysis of long-term optical monitoring observations and optical spectroscopic observations of the counterpart to CXOU J205847.5+414637 (high mass X-ray binary system). We search for a variability in the light curve of Be star. We used differential magnitudes in the time series analysis. The variability search in the optical light curve was made by using different algorithms. The reduction and analysis of spectra were done by using MIDAS and its suitable packages. We have performed a frequency search which gave us the value 2.404 1/day. This value is attributed to the non-radial pulsation of Be star. H alpha emission line profiles always show double-peaked emissions with a mean equivalent width of 2.31 \pm 0.19 \AA ~and a peak separation of 516 \pm 45 km/s. This suggests that Be star disk is still present. CXOU J205847.5+414637 is in X-ray quiescent state.Comment: 8 pages, 9 figures. To appear at Astronomy and Astrophysic

Work addiction and its relation with dark personality traits: a cross-sectional study with private sector employees

Personality traits have been extensively studied to understand different behavioral addictions. However, less is known about the relationship of employees’ dark personality traits and work addiction. The purpose of the present study was to examine the associations between the Big Five personality traits (i.e., extroversion, neuroticism, agreeableness, openness, conscientiousness) and dark personality traits (i.e., narcissism, Machiavellianism, psychopathy, sadism, and spitefulness) with work addiction. A total of 514 private sector employees completed a survey that included psychometric assessment tools for the aforementioned variables. Hierarchical regression analysis indicated that lower extroversion, lower openness to experience, higher narcissism, and higher spitefulness were positively associated with work addiction among private sector employees. The findings of the present study suggest that dark personality traits should also be taken into account in order to better understand work addiction among employees

Recent RXTE/ASM and ROTSEIIId Observations of EXO 2030+375

Using the archival RXTE/ASM and SWIFT/BAT observations, the new orbital phases of Type I outbursts of EXO 2030+375 are estimated. A possible correlation between the Type II outburst and optical brightness variations is investigated. In order to estimate the phases of Type I outbursts, we fitted Gaussian profiles to the RXTE/ASM and SWIFT/BAT light curves. The time corresponding to the maximum value of the profiles is treated as the arrival time of Type I outburst. We used differential magnitudes in the time-series analysis of the optical light curve. MIDAS and its suitable packages were used to reduce and analyze the spectra. Prior to the Type II outburst, orbital phases of Type I outbursts were delayed for 6 days after the periastron passage, which is consistent with findings of Wilson et al., (2002, 2005). After the giant Type II outburst, the phase of Type I outbursts underwent a sudden shift of 13 days after the periastron passage. The amplitudes of Type I outbursts were increased between MJD 52500 and 53500. These amplitudes then decreased for 10 orbital cycles until the Type II outburst was triggered. If the change of outburst amplitudes correlated with the mass accretion, then during the decrease of these amplitudes mass should be deposited in a disk around neutron star temporarily. The release of this stored mass may ignite the Type II outburst. We report that the optical light curve became fainter by 0.4 mag during the decrease of amplitude of the Type I outbursts. The observed H$\alpha$ profiles and their equivalent widths during the decay and after the giant outburst are consistent with previous observations of the system.Comment: to appear at Astronomy and Astrophysic

Status of the ROTSE-III telescope network

ROTSE-III is a homogeneous worldwide array of 4 robotic telescopes. They were designed to provide optical observations of γ-ray burst (GRB) afterglows as close as possible to the start of γ-ray emission. ROTSE-III is fulfilling its potential for GRB science, and provides optical observations for a variety of astrophysical sources in the interim between GRB events

Prompt Optical Detection of GRB 050401 with ROTSE-IIIa

The ROTSE-IIIa telescope at Siding Spring Observatory, Australia, detected prompt optical emission from Swift GRB 050401. In this letter, we present observations of the early optical afterglow, first detected by the ROTSE-IIIa telescope 33 s after the start of gamma-ray emission, contemporaneous with the brightest peak of this emission. This GRB was neither exceptionally long nor bright. This is the first prompt optical detection of a GRB of typical duration and luminosity. We find that the early afterglow decay does not deviate significantly from the power-law decay observable at later times, and is uncorrelated with the prompt gamma-ray emission. We compare this detection with the other two GRBs with prompt observations, GRB 990123 and GRB 041219a. All three bursts exhibit quite different behavior at early times.Comment: 4 pages, 3 figures. Accepted for publication in ApJ Letter

Optical Lightcurve & Cooling Break of GRB 050502A

We present lightcurves of the afterglow of GRB050502A, including very early data at t-t_{GRB} < 60s. The lightcurve is composed of unfiltered ROTSE-IIIb optical observations from 44s to 6h post-burst, R-band MDM observations from 1.6 to 8.4h post-burst, and PAIRITEL J H K_s observations from 0.6 to 2.6h post-burst. The optical lightcurve is fit by a broken power law, where t^{alpha} steepens from alpha = -1.13 +- 0.02 to alpha = -1.44 +- 0.02 at \~5700s. This steepening is consistent with the evolution expected for the passage of the cooling frequency nu_c through the optical band. Even in our earliest observation at 44s post-burst, there is no evidence that the optical flux is brighter than a backward extrapolation of the later power law would suggest. The observed decay indices and spectral index are consistent with either an ISM or a Wind fireball model, but slightly favor the ISM interpretation. The expected spectral index in the ISM interpretation is consistent within 1 sigma with the observed spectral index beta = -0.8 +- 0.1; the Wind interpretation would imply a slightly (~2 sigma) shallower spectral index than observed. A small amount of dust extinction at the source redshift could steepen an intrinsic spectrum sufficiently to account for the observed value of beta. In this picture, the early optical decay, with the peak at or below 4.7e14 Hz at 44s, requires very small electron and magnetic energy partitions from the fireball.Comment: 22 pages, including 3 tables and 1 figure, Accepted by Ap

The Anomalous Early Afterglow of GRB 050801

The ROTSE-IIIc telescope at the H.E.S.S. site, Namibia, obtained the earliest detection of optical emission from a Gamma-Ray Burst (GRB), beginning only 21.8 s from the onset of Swift GRB 050801. The optical lightcurve does not fade or brighten significantly over the first ~250 s, after which there is an achromatic break and the lightcurve declines in typical power-law fashion. The Swift/XRT also obtained early observations starting at 69 s after the burst onset. The X-ray lightcurve shows the same features as the optical lightcurve. These correlated variations in the early optical and X-ray emission imply a common origin in space and time. This behavior is difficult to reconcile with the standard models of early afterglow emission.Comment: 5 pages, 1 figure. Accepted for publication in ApJ Letter

The Optical Luminosity Function of Gamma-ray Bursts deduced from ROTSE-III Observations

We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs), and those with upper limits (40 GRBs). The $R$ band fluxes 100s after the onset of the burst for these two sub-samples are derived. The optical LFs at 100s are fitted by assuming that the co-moving GRB rate traces the star-formation rate. The detection function of ROTSE-III is taken into account during the fitting of the optical LFs by using Monte Carlo simulations. We find that the cumulative distribution of optical emission at 100s is well-described with an exponential rise and power-law decay (ERPLD), broken power-law (BPL), and Schechter LFs. A single power-law (SPL) LF, on the other hand, is ruled out with high confidence.Comment: 26 pages, 3 figures, ApJ accepte

Exploring Broadband GRB Behavior During gamma-ray Emission

The robotic ROTSE-III telescope network detected prompt optical emission contemporaneous with the gamma-ray emission of Swift events GRB051109A and GRB051111. Both datasets have continuous coverage at high signal-to-noise levels from the prompt phase onwards, thus the early observations are readily compared to the Swift XRT and BAT high energy detections. In both cases, the optical afterglow is established, declining steadily during the prompt emission. For GRB051111, there is evidence of an excess optical component during the prompt emission. The component is consistent with the flux spectrally extrapolated from the gamma-rays, using the gamma-ray spectral index. A compilation of spectral information from previous prompt detections shows that such a component is unusual. The existence of two prompt optical components - one connected to the high-energy emission, the other to separate afterglow flux, as indicated in GRB051111 - is not compatible with a simple ``external-external'' shock model for the GRB and its afterglow.Comment: ApJ accepted. 32 pages (in preprint form), 5 tables, 5 figure