Related papers: A likely inverse-Compton emission from the Type II…
A recent re-determination of the non-thermal component of the hard X-ray to soft gamma-ray emission from the Galactic ridge, using the SPI instrument on the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) Observatory, is shown to…
We present contemporaneous optical and infrared photometric observations of the type IIn SN 1998S covering the period between 11 and 146 days after discovery. The infrared data constitute the first ever infrared light curves of a type IIn…
Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray…
Type IIb supernovae are believed to originate from core-collapse progenitors having kept only a very thin hydrogen envelope. We aim to explore how some physical factors, such as rotation, metallicity, overshooting, and the initial orbital…
The Cygnus region is a vast star-forming complex harbouring a population of powerful objects, including massive star clusters and associations, Wolf-Rayet stars, pulsars, and supernova remnants. The multi-wavelength picture is far from…
We show that the prompt and afterglow X-ray emission of GRB060218, as well as its early (t<=1 d) optical-UV emission, can be explained by a model in which a radiation- mediated shock propagates through a compact progenitor star into a dense…
We investigate the origin of the H$\alpha$-like structure seen in late-phase nebular spectra of type IIb supernovae (SNe IIb) at $\sim 200$ days after the explosion. We compare the luminosities of emission lines in the nebular spectra with…
Magnetars are a subclass of neutron stars with ultra-strong surface magnetic fields. Some magnetars exhibit persistent hard X-ray emission, characterized by power-law tails with photon indices around 1--1.5, extending from ${\sim}$10 keV to…
We examine pre-supernova Chandra images to find X-ray luminosities of type Ia supernova progenitors. At present, we have one possible direct detection and upper limits for the X-ray luminosities of a number of other supernova progenitors.…
We present an extensive ($\sim$ 1200 d) photometric and spectroscopic monitoring of the Type IIn supernova (SN) 2012ab. After a rapid initial rise leading to a bright maximum (M$_{R}$ = $-$19.39 mag), the light curves show a plateau lasting…
We discuss growing evidence that pulsar high energy is emission is generated via Inverse Compton mechanism. We reproduce the broadband spectrum of Crab pulsar, from UV to very high energy gamma-rays - nearly ten decades in energy, within…
Inverse Compton scattering by relativistic electrons produces a major component of the diffuse emission from the Galaxy. The photon fields involved are the cosmic microwave background and the interstellar radiation field from stars and…
We present an optical spectropolarimetric observation of the unique Type Ib supernova (SN) 2005bf at 8 days after the second maximum. The data, combined with the polarization spectrum taken at 6 days before the second maximum (Maund et al.…
Thermal X-ray emission which is simultaneous with the prompt gamma-rays has been detected for the first time from a supernova connected with a gamma-ray burst (GRB), namely GRB060218/SN2006aj. It has been interpreted as arising from the…
We present nebular spectra of the nearby Type IIb supernova (SN) 2011dh taken between 201 and 678 days after core collapse. At these late times, SN 2011dh exhibits strong emission lines including a very broad and persistent H{\alpha}…
We investigate broad-band emission from supernova ejecta powered by a relativistic wind from a central compact object. A recent two-dimensional hydrodynamic simulation studying the dynamical evolution of supernova ejecta with a central…
We present photometric and spectroscopic data of the type IIb supernova (SN) 2024abfo in NGC 1493 (at 11 Mpc). The ATLAS survey discovered the object just a few hours after the explosion, and observed a fast rise on the first day. Signs of…
We study X-ray spectra of Cyg X-3 from BeppoSAX, taking into account absorption and emission in the strong stellar wind of its companion. We find the intrinsic X-ray spectra are well modelled by disc blackbody emission, its upscattering by…
The discovery of a population of superluminous supernovae (SLSNe), with peak luminosities a factor of ~100 brighter than normal SNe (typically SLSNe have M_V <-21), has shown an unexpected diversity in core-collapse supernova properties.…
In the hypernova/collapsar model of gamma-ray bursts, it is natural that radiation is emitted by the inner engine for some time after the burst. This has been discussed as a possible source of the X-ray line emission observed in some…