'On the difference between the short and long gamma-ray bursts'

We argue that the distributions of both the intrinsic fluence and the intrinsic duration of the gamma-ray emission in gamma-ray bursts from the BATSE sample are well represented by log-normal distributions, in which the intrinsic dispersion is much larger than the cosmological time dilatation and redshift effects. We perform separate bivariate log-normal distribution fits to the BATSE short and long burst samples. The bivariate log-normal behaviour results in an ellipsoidal distribution, whose major axis determines an overall statistical relation between the fluence and the duration. We show that this fit provides evidence for a power-law dependence between the fluence and the duration, with a statistically significant different index for the long and short groups. We discuss possible biases, which might affect this result, and argue that the effect is probably real. This may provide a potentially useful constraint for models of long and short bursts.Comment: A.A. in press ; significantly revised version of astro-ph/0007438; 16 pages 5 PS figure

Gamma photometric redshifts for long gamma-ray bursts

It is known that the soft tail of the gamma-ray bursts' spectra show excesses from the exact power-law dependence. In this article we show that this departure can be detected in the peak flux ratios of different BATSE DISCSC energy channels. This effect allows to estimate the redshift of the bright long gamma-ray bursts in the BATSE Catalog. A verification of these redshifts is obtained for the 8 GRB which have both BATSE DISCSC data and measured optical spectroscopic redshifts. There is good correlation between the measured and esti redshifts, and the average error is $\Delta z \approx 0.33$. The method is similar to the photometric redshift estimation of galaxies in the optical range, hence it can be called as "gamma photometric redshift estimation". The estimated redshifts for the long bright gamma-ray bursts are up to $z \simeq 4$. For the the faint long bursts - which should be up to $z \simeq 20$ - the redshifts cannot be determined unambiguously with this method.Comment: accepted in A&A, 7 pages incl. 7 figure

A Semi-analytic Formulation for Relativistic Blast Waves with a Long-lived Reverse Shock

This paper performs a semi-analytic study of relativistic blast waves in the context of gamma-ray bursts (GRBs). Although commonly used in a wide range of analytical and numerical studies, the equation of state (EOS) with a constant adiabatic index is a poor approximation for relativistic hydrodynamics. Adopting a more realistic EOS with a variable adiabatic index, we present a simple form of jump conditions for relativistic hydrodynamical shocks. Then we describe in detail our technique of modeling a very general class of GRB blast waves with a long-lived reverse shock. Our technique admits an arbitrary radial stratification of the ejecta and ambient medium. We use two different methods to find dynamics of the blast wave: (1) customary pressure balance across the blast wave and (2) the "mechanical model". Using a simple example model, we demonstrate that the two methods yield significantly different dynamical evolutions of the blast wave. We show that the pressure balance does not satisfy the energy conservation for an adiabatic blast wave while the mechanical model does. We also compare two sets of afterglow light curves obtained with the two different methods.Comment: 33 pages, 9 figures, published in Ap

GeV-TeV and X-ray flares from gamma-ray bursts

The recent detection of delayed X-ray flares during the afterglow phase of gamma-ray bursts (GRBs) suggests an inner-engine origin, at radii inside the deceleration radius characterizing the beginning of the forward shock afterglow emission. Given the observed temporal overlapping between the flares and afterglows, there must be inverse Compton (IC) emission arising from such flare photons scattered by forward shock afterglow electrons. We find that this IC emission produces GeV-TeV flares, which may be detected by GLAST and ground-based TeV telescopes. We speculate that this kind of emission may already have been detected by EGRET from a very strong burst--GRB940217. The enhanced cooling of the forward shock electrons by the X-ray flare photons may suppress the synchrotron emission of the afterglows during the flare period. The detection of GeV-TeV flares combined with low energy observations may help to constrain the poorly known magnetic field in afterglow shocks. We also consider the self-IC emission in the context of internal-shock and external-shock models for X-ray flares. The emission above GeV from internal shocks is low, while the external shock model can also produce GeV-TeV flares, but with a different temporal behavior from that caused by IC scattering of flare photons by afterglow electrons. This suggests a useful approach for distinguishing whether X-ray flares originate from late central engine activity or from external shocks.Comment: slightly shortened version, accepted for publication in ApJ Letters, 4 emulateapj pages, no figure

Dependence of the optical brightness on the gamma and X-ray properties of GRBs

The Swift satellite made a real break through with measuring simultaneously the gamma X-ray and optical data of GRBs, effectively. Although, the satellite measures the gamma, X-ray and optical properties almost in the same time a significant fractions of GRBs remain undetected in the optical domain. In a large number of cases only an upper bound is obtained. Survival analysis is a tool for studying samples where a part of the cases has only an upper (lower) limit. The obtained survival function may depend on some other variables. The Cox regression is a way to study these dependencies. We studied the dependence of the optical brightness (obtained by the UVOT) on the gamma and X-ray properties, measured by the BAT and XRT on board of the Swift satellite. We showed that the gamma peak flux has the greatest impact on the afterglow's optical brightness while the gamma photon index and the X-ray flux do not. This effect probably originates in the energetics of the jet launched from the central engine of the GRB which triggers the afterglow.Comment: 2012 Fermi Symposium proceedings - eConf C12102

Gamma-ray Burst Afterglow with Continuous Energy Injection: Signature of a Highly-Magnetized Millisecond Pulsar

We investigate the consequences of a continuously injecting central engine on the gamma-ray burst afterglow emission, focusing more specifically on a highly-magnetized millisecond pulsar engine. For initial pulsar parameters within a certain region of the parameter space, the afterglow lightcurves are predicted to show a distinctive achromatic bump feature, the onset and duration of which range from minutes to months, depending on the pulsar and the fireball parameters. The detection of or upper limits on such features would provide constraints on the burst progenitor and on magnetar-like central engine models. An achromatic bump such as that in GRB 000301C afterglow may be caused by a millisecond pulsar with P0=3.4 millisecond and Bp=2.7e14 Gauss.Comment: 5 pages, emulateapj style, to appear in ApJ Letters, updated with the accepted version, a few corrections are mad

Detailed Classification of Swift's Gamma-Ray Bursts

Earlier classification analyses found three types of gamma-ray bursts (short, long and intermediate in duration) in the BATSE sample. Recent works have shown that these three groups are also present in the RHESSI and the BeppoSAX databases. The duration distribution analysis of the bursts observed by the Swift satellite also favors the three-component model. In this paper, we extend the analysis of the Swift data with spectral information. We show, using the spectral hardness and the duration simultaneously, that the maximum likelihood method favors the three-component against the two-component model. The likelihood also shows that a fourth component is not needed.Comment: Accepted for publication in The Astrophysical Journa

Temporal-spatial Patterns of Noctuinae Communities (Lep. Noctuidae) in Hungarian Apple Orchards (Apple Ecosystem Research)

In our present study we aimed to recognize the temporal and spatial patterns of Noctuinae communities (Lep.Noctuidae) of four differently managed apple orchards laying in different localities of Hungary. Data were obtained by light trap collection. The quantitative data resulting from our investigations were analyzed by multivariate methods and were also analyzed by their diversity characteristics.As a result connections were found regarding the diversities of species and individuals, the patterns of occurrence and phenological properties. The studies were based on 8497 individuals of 39 species

A possible interrelation between the estimated luminosity distances and internal extinctions of type Ia supernovae

We studied the statistical properties of the luminosity distance and internal extinction data of type Ia supernovae in the lists published by Tonry et al. (2003) and Barris et al. (2004). After selecting the luminosity distance in an empty Universe as a reference level we divided the sample into low $z<0.25$ and high $z \ge 0.25$ parts. We further divided these subsamples by the median of the internal extinction. Performing sign tests using the standardized residuals between the estimated logarithmic luminosity distances and those of an empty universe, on the four subsamples separately, we recognized that the residuals were distributed symmetrically in the low redshift region, independently from the internal extinction. On the contrary, the low extinction part of the data of $z \ge 0.25$ clearly showed an excess of the points with respect to an empty Universe which was not the case in the high extinction region. This diversity pointed to an interrelation between the estimated luminosity distance and internal extinction. To characterize quantitatively this interrelation we introduced a hidden variable making use of the technics of factor analysis. After subtracting that part of the residual which was explained by the hiddenmaking use of the technics of factor analysis. After subtracting that part of the residual which was explained by the hidden variable we obtained luminosity distances which were already free from interrelation with internal extinction. Fitting the corrected luminosity distances with cosmological models we concluded that the SN Ia data alone did not exclude the possibility of the $\Lambda=0$ solution

UV/Optical Emission Accompanying Gamma-ray Burst

We discuss the possible simultaneously UV/optical emission accompanying Gamma-ray bursts (GRBs). We show that as long as the intrinsic spectrum of GRB can extend to $\sim$10 GeV or higher, there is a large amount of relativistic $e^\pm$ pairs generated due to the annihilation of the soft $\gamma-$rays with the very energetic photons, which dominates over the electrons/positrons associated with the fireball, no matter the fireball is highly magnetized or not (For the highly magnetized fireball, the magnetic field is ordered, the high linear polarization of the multi-wavelength emission is expected). We find that these $e^\pm$ pairs can power an UV flash with $m\simeq 12-13{\rm th}$ magnitude, and the corresponding optical emission can be up to $m_{\rm R}\simeq15-16{\rm th}$ magnitude. Such bright UV emission can be detected by the upcoming satellite Swift, planned for launch in early 2004. The behavior of the optical-UV spectrum ($F_{\nu}\propto \nu^{5/2}$) differs significantly from that of the reverse shock emission ($F_{\nu}\propto \nu^{-\beta/2}$, $\beta \simeq 2.2$), which is a signature of the emission accompanying with GRB. The mild optical emission can be detected with the ROTSE-IIIa telescope system, if the response to the GRB alert is fast enough.Comment: 5 pages, no figures. MNRAS in pres