- ID:
- ivo://CDS.VizieR/J/ApJ/898/14
- Title:
- GRB spectral properties from Fermi and Swift
- Short Name:
- J/ApJ/898/14
- Date:
- 21 Mar 2022 07:04:24
- Publisher:
- CDS
- Description:
- We statistically examine the gamma-ray burst (GRB) photon indices obtained by the Fermi-GBM and Fermi-LAT observations and compare the LAT GRB photon indices to the GBM GRB photon indices. We apply the jitter radiation to explain the GRB spectral diversities in the high-energy bands. In our model, the jitter radiative spectral index is determined by the spectral index of the turbulence. We classify GRBs into three classes depending on the shape of the GRB high-energy spectrum when we compare the GBM and LAT detections: the GRB spectrum is concave (GRBs turn out to be softer and are labeled as S-GRBs), the GRB spectrum is convex (GRBs turn out to be harder and are labeled as H-GRBs), and the GRBs have no strong spectral changes (labeled as N-GRBs). A universal Kolmogorov index 7/3 in the turbulent cascade is consistent with the photon index of the N-GRBs. The S-GRB spectra can be explained by the turbulent cascade due to the kinetic magnetic reconnection with the spectral index range of the turbulence from 8/3 to 3.0. The H-GRB spectra originate from the inverse turbulent cascade with the spectral index range of the turbulence from 2.0 to 3.5 that occurred during the large lengthscale magnetic reconnection. Thus, the GRB radiative spectra are diversified because the turbulent cascade modifies the turbulent energy spectrum. More observational samples are expected in the future to further identify our suggestions.
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Search Results
- ID:
- ivo://nasa.heasarc/gusbad
- Title:
- GRBs Uniformly Selected from BATSE Archival Data (Version 2.1)
- Short Name:
- BATSE/GUSBAD
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The GUSBAD (Gamma-ray bursts Uniformly Selected from BATSE Archival Data) Catalog is based on BATSE DISCLA data at a time resolution of 1.024 seconds for the full 9.1 years of the Compton Gamma-Ray Observatory (CGRO) mission from April 19, 1991 until May 26, 2000 (corresponding to Truncated Julian Dates from 8365 to 11690). This catalog lists over 2200 gamma-ray bursts (GRBs). Selection of GRBs for the GUSBAD Catalog requires a 5-sigma excess over the background in two of the BATSE detectors over the energy range 50-300 keV. The search covers the entire mission except when CGRO was over particular geographic regions or during one of 199,964 time windows when DISCLA data were missing or contaminated. The classification as GRB or non-GRB of the 6236 events that were produced by the software trigger was aided by correlating the times and positions of the events against the Current BATSE Burst Catalog. There are 589 GRBs in the GUSBAD Catalog that are not included in the Current BATSE Burst Catalog. The GUSBAD catalog is uniform in the sense that the detection criterion is the same throughout and that the properties given in the catalog are available for every burst. The detection and the derivation of the properties listed in the catalog were carried out automatically, except for some rare instances. This makes the catalog especially suitable for statistical work and simulations, such as used in the evaluation of V/Vmax. The procedure used to detect and classify the bursts has been described in Schmidt (2004). This database table was last updated by the HEASARC in April 2005 using the file GUSBADcat.dat containing version 2.1 of the catalog, which was obtained from the catalog author's web site at <a href="http://www.astro.caltech.edu/~mxs/grb/GUSBAD/">http://www.astro.caltech.edu/~mxs/grb/GUSBAD/</a> <p> Comments or questions about the contents of the GUSBAD Catalog are welcomed by the author who can be contacted at mxs@astro.caltech.edu. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/729
- Title:
- GRB Swift X-ray light curves analysis
- Short Name:
- J/MNRAS/428/729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of 'memory' of the prompt {gamma}-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt {gamma}-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the {gamma}-ray energy to the prompt spectral peak energy of both long and short GRBs: E_X,iso_{prop.to}E^1.00+/-0.06^_{gamma},iso_/E^0.60+/-0.10^_pk_.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/76
- Title:
- 6 GRBs with Swift XRT and Fermi GBM obs.
- Short Name:
- J/ApJ/880/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The jet photosphere has been proposed as the origin for the gamma-ray burst (GRB) prompt emission. In many such models, characteristic features in the spectra appear below the energy range of the Fermi Gamma-ray Burst Monitor (GBM) detectors, so joint fits with X-ray data are important in order to assess the photospheric scenario. Here we consider a particular photospheric model which assumes localized subphotospheric dissipation by internal shocks in a non-magnetized outflow. We investigate it using Bayesian inference and a sample of eight GRBs with known redshifts which are observed simultaneously with Fermi GBM and the Swift X-ray Telescope (XRT). This provides us with an energy range of 0.3keV-40MeV and much tighter parameter constraints. We analyze 32 spectra and find that 16 are well described by the model. We also find that the estimates of the bulk Lorentz factor, {Gamma}, and the fireball luminosity, L_0,52_, decrease while the fraction of dissipated energy, {epsilon}_d_, increases in the joint fits compared to GBM-only fits. These changes are caused by a small excess of counts in the XRT data, relative to the model predictions from fits to GBM-only data. The fact that our limited implementation of the physical scenario yields 50% accepted spectra is promising, and we discuss possible model revisions in the light of the new data. Specifically, we argue that the inclusion of significant magnetization, as well as removing the assumption of internal shocks, will provide better fits at low energies.
- ID:
- ivo://CDS.VizieR/J/ApJ/772/73
- Title:
- GRB with early-time optical emission
- Short Name:
- J/ApJ/772/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength analysis of Swift gamma-ray burst GRB 090727, for which optical emission was detected during the prompt {gamma}-ray emission by the 2m autonomous robotic Liverpool Telescope and subsequently monitored for a further two days with the Liverpool and Faulkes Telescopes. Within the context of the standard fireball model, we rule out a reverse shock origin for the early-time optical emission in GRB 090727 and instead conclude that the early-time optical flash likely corresponds to emission from an internal dissipation process. Putting GRB 090727 into a broader observational and theoretical context, we build a sample of 36 {gamma}-ray bursts (GRBs) with contemporaneous early-time optical and {gamma}-ray detections. From these GRBs, we extract a sub-sample of 18 GRBs, which show optical peaks during prompt {gamma}-ray emission, and perform detailed temporal and spectral analysis in {gamma}-ray, X-ray, and optical bands. We find that in most cases early-time optical emission shows sharp and steep behavior, and notice a rich diversity of spectral properties. Using a simple internal shock dissipation model, we show that the emission during prompt GRB phase can occur at very different frequencies via synchrotron radiation. Based on the results obtained from observations and simulation, we conclude that the standard external shock interpretation for early-time optical emission is disfavored in most cases due to sharp peaks ({Delta}t/t<1) and steep rise/decay indices, and that internal dissipation can explain the properties of GRBs with optical peaks during {gamma}-ray emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/45
- Title:
- GRB X-ray afterglows light curves analysis
- Short Name:
- J/ApJ/826/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a correlation between the average temporal decay ({alpha}_X,avg,>200s_) and early-time luminosity (L_X,200s_) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200s after the {gamma}-ray trigger. The luminosity-average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. (2012MNRAS.426L..86O, 2015MNRAS.453.4121O) in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/59
- Title:
- GRB X-ray flare temporal and spectral properties
- Short Name:
- J/ApJ/884/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gamma-ray bursts (GRBs) can be divided into three subclasses: X-ray flash (XRF), X-ray rich (XRR), and classical GRB (C-GRB). An X-ray flare is the rebrightening emission shown in the early X-ray afterglow of some GRBs. In this paper, we comprehensively examine the X-ray flare properties among XRF, XRR, and C-GRB subclasses. We utilize the XRF, XRR, and C-GRB subclass samples obtained from the Swift-BAT3 catalog, and the X-ray flare observational properties are collected from Falcone+ (2007ApJ...671.1921F), Chincarini+ (2010MNRAS.406.2113C), and Yi+ (2016, J/ApJS/224/20). We find that XRFs and XRRs have more bright X-ray flares than C-GRBs. The ratio of the X-ray flare fluence to the prompt emission fluence has different distributions between XRF and C-GRB subclasses. The linear correlation between the duration and the peak time of the X-ray flares is also different between XRF and C-GRB subclasses. We are inclined to identify the GRBs with the bright X-ray flares as XRFs or XRRs. We discuss some issues that are related to the XRF/XRR/C-GRB classification. We also caution the selection effects and the instrument bias in our investigation. Large samples are required in the future to further confirm our results.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/95
- Title:
- g'RcIcJ photometry of the hot Uranus GJ3470b
- Short Name:
- J/ApJ/770/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical (g', R_c_, and I_c_) to near-infrared (J) simultaneous photometric observations for a primary transit of GJ3470b, a Uranus-mass transiting planet around a nearby M dwarf, by using the 50cm MITSuME telescope and the 188cm telescope, both at the Okayama Astrophysical Observatory. From these data, we derive the planetary mass, radius, and density as 14.1 +/-1.3M_{Earth}_, 4.32_-0.10_^+0.21^R_{Earth}_, and 0.94+/-0.12g/cm3, respectively, thus confirming the low density that was reported by Demory et al. (2013ApJ...768..154D) based on the Spitzer/IRAC 4.5{mu}m photometry (0.72_-0.12_^+0.13^g/cm3). Although the planetary radius is about 10% smaller than that reported by Demory et al., this difference does not alter their conclusion that the planet possesses a hydrogen-rich envelope whose mass is approximately 10% of the planetary total mass. On the other hand, we find that the planet-to-star radius ratio (R_p_/R_s_) in the J band (0.07577_-0.00075_^+0.00072^) is smaller than that in the I_c_(0.0802+/-0.0013) and 4.5{mu}m (0.07806_-0.00054_^+0.00052^) bands by 5.8%+/-2.0% and 2.9%+/-1.1%, respectively. A plausible explanation for the differences is that the planetary atmospheric opacity varies with wavelength due to absorption and/or scattering by atmospheric molecules. Although the significance of the observed R_p_/R_s_variations is low, if confirmed, this fact would suggest that GJ3470b does not have a thick cloud layer in the atmosphere. This property would offer a wealth of opportunity for future transmission-spectroscopic observations of this planet to search for certain molecular features, such as H_2_O, CH_4_, and CO, without being prevented by clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/352/39
- Title:
- Great Attractor region redshifts
- Short Name:
- J/A+A/352/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the third of a series of papers on large-scale structures behind the southern Milky Way, we report here on redshifts obtained at the South African Astronomical Observatory (SAAO) in the Great Attractor region (318{deg}<~l<~340{deg}, |b|<=10{deg}, Woudt, 1998, Ph. D. Thesis, University of Cape Town). This region encompasses the peak in the reconstructed mass density field, associated with the Great Attractor (Kolatt et al., 1995MNRAS.275..797K, Dekel et al., 1999ApJ...522....1D) and covers the crossing of the Supergalactic Plane with the Galactic Plane. Our deep optical galaxy search in the Zone of Avoidance (ZOA) in this region (Woudt, 1998, Ph. D. Thesis, University of Cape Town) has resulted in the detection of 4423 galaxies with observed diameters larger than 0.2arcmin. We have obtained reliable redshifts for 309 galaxies of the 4423 galaxies with the ``Unit'' spectrograph (first with a Reticon, then with a CCD detector) at the 1.9-m telescope of the SAAO. An additional 13 tentative redshifts are presented.
- ID:
- ivo://nasa.heasarc/gb6
- Title:
- Green Bank 6-cm (GB6) Radio Source Catalog
- Short Name:
- GB6
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the Green Bank 6-cm (GB6) Radio Source Catalog. The Green Bank 4.85 GHz (6-cm wavelength) survey (Condon J.J., Broderick J.J., Seielstad G.A., Douglas K., & Gregory P.C. in 1994AJ....107.1829C) was made with the NRAO seven-beam receiver on the (former) 91m telescope during 1986 November and 1987 October. The final set of sky maps covering the declination band 0 deg < Dec. < +75 deg was constructed with data from both epochs. Its noise and position errors are nearly a factor of 2^(1/2) smaller than in the epoch 1987 maps, from which the 87GB Catalog (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/VIII/14">CDS Catalog <VIII/14></a>) of 54,579 sources stronger than S ~ 25mJy was extracted. Therefore, the new maps were used to make the GB6 catalog of 75,162 discrete sources with angular sizes phi <= 10.5 arcmin and flux densities S >= 18mJy. The GB6 weighted differential source counts S^(5/2)n(S) between 18 mJy and 7 Jy agree well with evolutionary models based on independent data. This table was created by the HEASARC in July 2003 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/VIII/40">CDS Catalog <VIII/40></a>. This is a service provided by NASA HEASARC .