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GRB 230812B is a bright and relatively nearby (z = 0.36) long gamma-ray burst (GRB) that has generated significant interest in the community and has thus been observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and submillimetre bands from the GRANDMA (Global Rapid Advanced Network for Multimessenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) of the GRB and compare with other analyses of this event. We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v ∼ 17 × 103 km s−1. We analyse the photometric data first using empirical fits of the flux and then with full Bayesian inference. We again strongly establish the presence of a supernova in the data, with a maximum (pseudo-)bolometric luminosity of 5.75 × 1042 erg s−1, at |$15.76^{+0.81}_{-1.21}$|  d (in the observer frame) after the trigger, with a half-max time width of 22.0 d. We compare these values with those of SN1998bw, SN2006aj, and SN2013dx. Our best-fitting model favours a very low density environment (⁠|$\log _{10}({n_{\rm ISM}/{\rm cm}^{-3}}) = -2.38^{+1.45}_{-1.60}$|⁠) and small values for the jet's core angle |$\theta _{\rm core} = 1.54^{+1.02}_{-0.81} \ \rm {deg}$| and viewing angle |$\theta _{\rm obs} = 0.76^{+1.29}_{-0.76} \ \rm {deg}$|⁠. GRB 230812B is thus one of the best observed afterglows with a distinctive supernova bump. [ABSTRACT FROM AUTHOR]

We study the luminosity function of long gamma-ray bursts (LGRBs) using the peak flux obtained from three LGRB samples with known redshifts: (a) a sample of 251 LGRBs from the Swift/BAT satellite/instrument; (b) a sample of 37 LGRBs from the Fermi/GBM telescope; (c) a sample of 152 GRBs from the Konus-Wind instrument. For the Swift/BAT and Fermi/GBM samples, we use data available on the Swift Burst Analyser websites (http://www.swift.ac.uk/burst%5fanalyser; (Evans at al. in Astron. Astrophys. 519:102, 2010)) and (http://swift.gsfc.nasa.gov/archive/grb/table/) and on the Fermi website (https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html; (Gruber et al. in Astrophys. J. Suppl. Ser. 211(1):12, 2014; von Kienlin et al. in Astrophys. J. Suppl. Ser. 211(1):13, 2014; Bhat et al. in Astrophys. J. Suppl. Ser. 223(2):28, 2016)) to calculate the luminosity at the peak of the flux by using a cut-off power-law spectrum (CPL). For the Konus-Wind sample, we use the Yonetoku correlation relationship (Yonetoku et al. in Publ. Astron. Soc. Jpn. 62:1495, 2010) to determine the isotropic luminosity from the energy at the peak of the flux measured in the source frame (Minaev and Pozanenko in Mon. Not. R. Astron. Soc. 492(2):1919, 2019). With these three samples (totalling 439 GRBs), we use the Monte Carlo method to synthesize 10,000 "artificial" GRBs similar to each real GRB by considering that each physical quantity observed obeys a normal distribution, where the tabulated value and uncertainty represent the mean and the 3 σ error. The results obtained for the luminosity function from our data samples are consistent with those published in previous works. [ABSTRACT FROM AUTHOR]

We use a sample of Swift gamma-ray bursts (GRBs) to analyze the Amati and Yonetoku correlations. The first relation is between E, the intrinsic peak energy of the prompt GRB emission, and E, the equivalent isotropic energy. The second relation is between E and L, the isotropic peak luminosity. We select a sample of 71 Swift GRBs that have a measured redshift and whose observed $E^{obs}_{p}$ is within the interval of energy 15-150 keV with a relative uncertainty of less than 70 %. We seek to find correlation relations for long-duration GRBs (LGRBs) with a peak photon flux P≥2.6 ph/cm/s. Uncertainties (error bars) on the values of the calculated energy flux P, the energy E, and the peak isotropic luminosity L are estimated using a Monte Carlo approach. We find 27 Swift LGRBs that satisfy all our constraints. Results of our analyses of the sample of 71 GRBs and the selected subsample (27 GRBs) are in good agreement with published results. The plots of the two relations for all bursts show a large dispersion around the best straight lines in the sample of 71 LGRBs but not so much in the subsample of 27 GRBs. [ABSTRACT FROM AUTHOR]

We examine the annihilation of positrons on polycyclic aromatic hydrocarbon (PAH) molecules in interstellar medium (ISM) conditions. We estimate the annihilation rates of positrons on PAHs by a semi-empirical approach. We show that PAHs can play a significant role in the overall Galactic positron annihilation picture and use the annihilation rates and International Gamma-Ray Astrophysics Laboratory Galactic emission measurements to constrain the number of PAHs present in the ISM. We find an upper limit of for the PAH abundance (by number, relative to hydrogen). [ABSTRACT FROM AUTHOR]

Abstract: The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM. [Copyright &y& Elsevier]

Presents information on a study that examined the processes which could lead to the observed enhancement of lithium and possibly other light elements on the main sequence companions of a number of X-ray novae. Model description; Results and discussion on the study.

Ever since the insightful analysis of the durations of gamma-ray bursts (GRBs) by Kouveliotou et al. (Astrophys. J. Lett. 413:101, 1993), GRBs have most often been classified into two populations: “short bursts” (shorter than 2.0 seconds) and “long bursts” (longer than 2.0 seconds). However, recent works have suggested the existence of an intermediate population in the bursts observed by the Swift satellite. Moreover, some researchers have questioned the universality of the 2.0-second dividing line between short and long bursts: some bursts may be short but actually result from collapsars, the physical mechanism behind normally long bursts, and some long ones may originate from mergers, the usual progenitors of short GRBs.In this work, we focus on GRBs detected by the Fermi satellite (which has a much higher detection rate than Swift and other burst-detecting satellites) and study the distribution of their durations measured in the observer’s reference frame and, for those with known redshifts, in the bursts’ reference frames. However, there are relatively few bursts with measured redshifts, and this makes an accurate study difficult. To overcome this problem, we follow Zhang and Wang (Astrophys. J. 852:1, 2018) and determine a “pseudo-redshift” from the correlation relation between the luminosity Lp and the energy Ep, both of which are calculated at the peak of the flux. Interestingly, we find that the uncertainties in the quantities observed and used in the determination of pseudo-redshifts, do affect the precision of the individual results significantly, but they keep the distribution of pseudo-redshifts very similar to that of the actual ones and thus allow us to use pseudo-redshifts for our statistical study. We briefly present the advantages and disadvantages of using pseudo-redshifts in this context.We use the reduced chi-square and the maximization of the log-likelihood to statistically analyze the distribution of Fermi GRB durations. Both methods show that the distribution of the observed (measured) and the intrinsic (source/rest frame) bursts durations are better represented by two groups/populations, rather than three. [ABSTRACT FROM AUTHOR]

Abstract: Several luminosity relations currently exist for long gamma-ray bursts (GRBs). Some were derived from the light curves; others were obtained from the spectra. In this study, we consider two of these luminosity relations: the time-lag, , relation and the variability, V, relation and investigate their possible dependence on (or “evolution” with) the redshift, z. The data we use are taken from Schaefer’s literature (Schaefer et al., 2007) in which 69 long gamma-ray bursts were analyzed. The method consists of binning the data by redshift interval, then writing the time-lag relation in the form and extracting the fit parameters A and B for each redshift bin; likewise, for the variability relation, which we write in the form . The objective is then to see whether the fitting parameters A and B evolve in any systematic way with the redshift. Our analysis indicates that both the A and B parameters do evolve with z in a systematic way for the lag-relation but not for the variability relation. A flat universe with , and is assumed. [Copyright &y& Elsevier]

The Oran region (Western Tell Atlas) was hit by two earthquakes on January 9th, 2008 (Mw = 4.7) and on June 6th, 2008 (Mw = 5.4). The two events were recorded by the national accelerographs network maintained by National Center of Applied Research in Earthquakes Engineering (CGS, Algiers). This work aims to characterize these two earthquakes in order to contribute to understand the seismotectonic context of the study region. We located the events using Grid Search Method based on P and S waves arrival time differences. The obtained hypocenter locations are, respectively, (0.457°W, 35.689°N, 11 km) and (0.576°W, 35.689°N, 8 km). We perform waveforms inversion to estimate the moment magnitude s and the seismic moments which are, respectively, Mw = 4.7, M 0 = 0.13 E+17 N m and Mw = 5.4, M 0 = 0.18 10 E+18 N m for the two events. Concerning the focal mechanism solutions both earthquakes yield reverse faulting with a compressional axes oriented NW-SE which is consistent with the active fault system trend in the study region. These two events occurred in an area which has been seismically quiet, since the event of December 1959 (Ms 4.7) and the historical major event of October 9th, 1790 (I 0 = IX-X; likely Ms ≥ 6.0). • Seismological study of two moderate earthquakes using locally recorded accelerometric data in northern Algeria: The January 9th (Mw 4.7) and the June 6th, 2008 (Mw 5.4) earthquakes. • Hypocenters localizations using the Grid search Method (GSM). • Determination of earthquakes parameters such as moment magnitude, seismic moment, and focal mechanism using waveforms inversion. • This study expands the seismotectonic knowledge of the Oran region, characterized by a seismic quietness since the December 1959 (Ms 4.7) and the October 9th, 1790 (I0= IX-X) earthquakes. [ABSTRACT FROM AUTHOR]