We report on the discovery of two emission features observed in the x-ray spectrum of the afterglow of the gamma-ray burst (GRB) of 16 December 1999 by the Chandra X-ray Observatory. These features are identified with the Ly α line and the narrow recombination continuum by hydrogenic ions of iron at a redshift z = 1.00 ± 0.02, providing an unambiguous measurement of the distance of a GRB. Line width and intensity imply that the progenitor of the GRB was a massive star system that ejected, before the GRB event, a quantity of iron ∼0.01 of the mass of the sun at a velocity ∼0.1 of the speed of light, probably by a supernova explosion.

GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized by the Neil Gehrels Swift Observatory in the outskirts of a spiral galaxy at z=0.1613, at a projected physical offset of ≈16 kpc from the galaxy's center. We present Xray, optical/nIR and radio observations of its counterpart and model them with two distinct components of emission: a standard afterglow, arising from the interaction of the relativistic jet with the surrounding medium, and a kilonova, powered by the radioactive decay of the sub-relativistic ejecta. Broadband modeling of the afterglow data reveals a weak reverse shock propagating backward into the jet, and a likely jet-break at ≈3.5 d. This is consistent with a structured jet seen slightly off-axis (θ view ∼ θ core ) while expanding into a low-density medium (n ≈10 −3 cm −3 ). Analysis of the kilonova properties suggests a rapid evolution toward red colors, similar to AT2017gfo, and a low nIR luminosity, possibly due to the presence of a long-lived neutron star. The global properties of the environment, the inferred low mass (M ej 0.006 M ⊙ ) and velocities (v ej 0.05c) of lanthanide-rich ejecta are consistent with a binary neutron star merger progenitor.

Abstract. We present BV RcIc broad-band flux spectra for the host galaxies of GRB 970508, GRB 980613, GRB 980703, GRB 990123 and GRB 991208 obtained with the 6-m telescope of SAO RAS. The comparison of the broad-band flux spectra of these host galaxies with the template spectral energy distributions (SEDs) of local starburst galaxies of different morphological types shows that the BV RcIc of the hosts are best fitted by the spectral properties of template SEDs of starburst galaxies and that there is a significant internal extinction in these host galaxies. We derived the absolute magnitudes of the GRB host galaxies making use of SEDs for the starburst galaxies. To create theoretical templates we performed the population synthesis modeling of the continuum spectral energy distribution of the host galaxies of GRB 970508 and GRB 980703 using different extinction laws (Cardelli et al. 1989 andCalzetti et al. 2000) and assuming burst and exponential scenarios of star formation. The comparison of BV RcIc broad-band flux spectra with the local starburst galaxies templates and theoretical templates as well as direct estimates (using Balmer emission lines) of the internal extinction shows that it is likely to be of great importance to take into account effects of the internal extinction in the host galaxies. From the energy distribution in the spectrum of the host galaxy of GRB 991208 and from the intensity of their spectral lines (with allowance for the effects of internal extinction) it follows that this is a GRB galaxy with the highest massive star-formation rate of all known GRB galaxies -up to hundreds of solar masses per year. The reduced luminosity of these dusty galaxies (e.g. for the host of GRB 970508 AV ∼ 2 mag, for the host of GRB 980703 AV ∼ 0.6 mag and for the host of GRB 991208 AV ∼ 2 mag) could explain the observational fact (it results independently from our BV RcIc photometry and from calculated spectral distribution for the subset of galaxies having been observed with the 6-m telescope): none of the observed GRB host galaxies with known distances is brighter than the local galaxies with the luminosity L * (where L * is the "knee" of the local luminosity function).

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We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M 61. Photometric data in the X-rays, ultraviolet and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ∼ 98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. (2010) indicates that it is a less energetic event (∼ 5 × 10 50 erg). However, the light curve indicates that the production of radioactive 56 Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of A V ∼ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesized 56 Ni mass of ∼ 0.015M ⊙ . Employing semi-analytical formulae (Litvinova & Nadezhin 1985), we derived a pre-SN radius of ∼ 126R ⊙ , an explosion energy of ∼ 5.4 × 10 50 erg and a total ejected mass of ∼ 16.7M ⊙ . The latter indicates that the zero age main-sequence mass of the progenitor did not exceed 20M ⊙ . Considering the above properties of SN 2008in and its occurrence in a region of sub-solar metallicity ([O/H] ∼ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star.

Abstract. We present the results of broad-band photometry of the nearby middle-aged radio pulsar PSR B0656+14 and its neighborhood obtained with the 6-meter telescope of the SAO RAS and with the Hubble Space Telescope. The broad-band spectral flux Fν of the pulsar decreases with increasing frequency in the near-IR range and increases with frequency in the near-UV range. The increase towards UV can be naturally interpreted as the Rayleigh-Jeans tail of the soft thermal component of the X-ray spectrum emitted from the surface of the cooling neutron star. Continuation of the power-law component, which dominates in the high-energy tail of the X-ray spectrum, to the IR-optical-UV frequencies is consistent with the observed fluxes. This suggests that the nonthermal pulsar radiation may be of the same origin in a broad frequency range from IR to hard X-rays. We also studied 4 objects detected within 5 from the pulsar.

We present broad band photometry and spectroscopic observations of the host galaxy of GRB 030329. Analysis of the spectral emission lines shows that the host is likely a low metallicity galaxy (Z ∼ 0.004). The spectral energy distribution (SED) constructed with the photometric points has been fitted using synthetic and observational templates. The best SED fit is obtained with a starburst template with an age of ∼150 Myr and an extinction A v ∼ 0.6. We find that the GRB 030329 host galaxy is a subluminous galaxy (L ∼ 0.016 L ) with a stellar mass of 10 8 M . Three independent diagnostics, based on the restframe UV continuum, the [O ii], and the Balmer emission lines, provide a consistent unextinguished star formation rate of ∼0.6 M yr −1 , implying a high unextinguished specific star formation rate (∼34 M yr −1 (L/L ) −1 ). We estimate that the unextinguished specific star formation rate of the GRB 030329 host is higher than ∼93.5% of the galaxies at a similar redshift.

We present photometry and spectroscopy of the Type IIP supernova (SN IIP) 2009bw in UGC 2890 from a few days after the outburst to 241 d. The light curve of SN 2009bw during the photospheric phase is similar to that of normal SNe IIP but with a brighter peak and plateau ( mag,  mag). The luminosity drop from the photospheric to the nebular phase is one of the fastest ever observed, ∼2.2 mag in about 13 d. The radioactive tail of the bolometric light curve indicates that the amount of ejected 56Ni is ≈0.022 M⊙. The photospheric spectra reveal high‐velocity lines of Hα and Hβ until about 105 d after the shock breakout, suggesting a possible early interaction between the SN ejecta and pre‐existent circumstellar material, and the presence of CNO elements. By modelling the bolometric light curve, ejecta expansion velocity and photospheric temperature, we estimate a total ejected mass of ∼8–12 M⊙, a kinetic energy of ∼0.3 foe and an initial radius of ∼3.6–7 × 1013 cm.