Discovery of a jet-like structure with overionized plasma in the SNR IC443

IC443 is a supernova remnant located in a quite complex environment since it interacts with nearby clouds. Indications for the presence of overionized plasma have been found though the possible physical causes of overionization are still debated. Moreover, because of its peculiar position and proper motion, it is not clear if the pulsar wind nebula (PWN) within the remnant is the relic of the IC443 progenitor star or just a rambling one seen in projection on the remnant. Here we address the study of IC443 plasma in order to clarify the relationship PWN-remnant, the presence of overionization and the origin of the latter. We analyzed two \emph{XMM-Newton} observations producing background-su…

Detection of GRB 060927 at z = 5.47: Implications for the Use of Gamma-Ray Bursts as Probes of the End of the Dark Ages

We report on follow-up observations of the GRB 060927 using the ROTSE-IIIa telescope and a suite of larger aperture ground-based telescopes. An optical afterglow was detected 20 s after the burst, the earliest rest-frame detection of optical emission from any GRB. Spectroscopy performed with the VLT about 13 hours after the trigger shows a continuum break at lambda ~ 8070 A produced by neutral hydrogen absorption at z~5.6. We also detect an absorption line at 8158 A which we interpret as SiII at z=5.467. Hence, GRB 060927 is the second most distant GRB with a spectroscopically measured redshift. The shape of the red wing of the spectral break can be fitted by a damped Lyalpha profile with a…

Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow

GRB 060614 is a remarkable GRB observed by Swift with puzzling properties, which challenge current progenitor models. The lack of any bright SN down to very strict limits and the vanishing spectral lags are typical of short GRBs, strikingly at odds with the long (102s) duration of this event. Here we present spectral and temporal analysis of the Swift observations. We show that the burst presents standard optical, UV and X-ray afterglows. An achromatic break is observed simultaneously in optical and X-rays, at a time consistent with the break in the R-band light curve measured by the VLT. The achromatic behaviour and the consistent post-break decay slopes make GRB 060614 one of the best exa…

GRB 070311: a direct link between the prompt emission and the afterglow

We present prompt gamma-ray, early NIR/optical, late optical and X-ray observations of the peculiar GRB 070311 discovered by INTEGRAL, in order to gain clues on the mechanisms responsible for the prompt gamma-ray pulse as well as for the early and late multi-band afterglow of GRB 070311. We fitted with empirical functions the gamma-ray and optical light curves and scaled the result to the late time X-rays. The H-band light curve taken by REM shows two pulses peaking 80 and 140 s after the peak of the gamma-ray burst and possibly accompanied by a faint gamma-ray tail. Remarkably, the late optical and X-ray afterglow underwent a major rebrightening between 3x10^4 and 2x10^5 s after the burst …

On the metal abundances inside mixed-morphology supernova remnants: the case of IC 443  and G166.0+4.3

Recent developments on the study of mixed morphology supernova remnants (MMSNRs) have revealed the presence of metal rich X-ray emitting plasma inside a fraction of these remnant, a feature not properly addressed by traditional models for these objects. Radial profiles of thermodynamical and chemical parameters are needed for a fruitful comparison of data and model of MMSNRs, but these are available only in a few cases. We analyze XMM-Newton data of two MMSNRs, namely IC443 and G166.0+4.3, previously known to have solar metal abundances, and we perform spatially resolved spectral analysis of the X-ray emission. We detected enhanced abundances of Ne, Mg and Si in the hard X-ray bright peak i…

Exploring Broadband GRB Behavior During gamma-ray Emission

The robotic ROTSE-III telescope network detected prompt optical emission contemporaneous with the gamma-ray emission of Swift events GRB051109A and GRB051111. Both datasets have continuous coverage at high signal-to-noise levels from the prompt phase onwards, thus the early observations are readily compared to the Swift XRT and BAT high energy detections. In both cases, the optical afterglow is established, declining steadily during the prompt emission. For GRB051111, there is evidence of an excess optical component during the prompt emission. The component is consistent with the flux spectrally extrapolated from the gamma-rays, using the gamma-ray spectral index. A compilation of spectral …

Swift observations of GRB 051109A

Different progenitors of short hard gamma-ray bursts

We consider the spatial offsets of short hard gamma-ray bursts (SHBs) from their host galaxies. We show that all SHBs with extended duration soft emission components lie very close to their hosts. We suggest that NS-BH binary mergers offer a natural explanation for the properties of this extended duration/low offset group. SHBs with large offsets have no observed extended emission components and are less likely to have an optically detected afterglow, properties consistent with NS-NS binary mergers occurring in low density environments.

The flaring afterglow of GRB 050730

We present a detailed spectral and temporal analysis of Swift and XMM-Newton observations of GRB 050730. The X-ray afterglow of GRB 050730 was found to decline with time with intense flaring activity superimposed. Evidence of flaring activity in the early UVOT optical afterglow, simultaneous with that observed in the X-ray band, was found. Strong spectral evolution in the X-ray energy band during the flaring activity was present.

Rest frame light curves of Swift GRBs

Spatial distribution of X-ray emitting ejecta in Tychos SNR: indications of shocked Titanium

Young supernova remnants show a characteristic ejecta-dominated X-ray emission that allows us to probe the products of the explosive nucleosynthesis processes and to ascertain important information about the physics of the supernova explosions. Hard X-ray observations have recently revealed the radioactive decay lines of 44Ti at ~67.9 keV and ~78.4 keV in the Tycho's SNR. We here analyze the set of XMM-Newton archive observations of the Tycho's SNR. We produce equivalent width maps of the Fe K and Ca XIX emission lines and find indications for a stratification of the abundances of these elements and significant anisotropies. We then perform a spatially resolved spectral analysis by identify…

The exceptionally extended flaring activity in the X-ray afterglow of GRB 050730 observed with Swift and XMM-Newton

We present the results of a detailed spectral and temporal analysis of Swift and XMM-Newton observations of the high redshift (z=3.969) GRB 050730. The X-ray afterglow of GRB 050730 was found to decline with time with superimposed intense flaring activity that extended over more than two orders of magnitude in time. Seven distinct re-brightening events starting from 236 s up to 41.2 ks after the burst were observed. The underlying decay of the afterglow was well described by a double broken power-law model with breaks at t_1= 237 +/- 20 s and t_2 = 10.1 (-2.2) (+4.6) ks. The temporal decay slopes before, between and after these breaks were alpha_1 = 2.1 +/- 0.3, alpha_2 = 0.44 (-0.08) (+0.1…

Swift Observations of GRB 070110: An Extraordinary X-Ray Afterglow Powered by the Central Engine

We present a detailed analysis of Swift multi-wavelength observations of GRB 070110 and its remarkable afterglow. The early X-ray light curve, interpreted as the tail of the prompt emission, displays a spectral evolution already seen in other gamma-ray bursts. The optical afterglow shows a shallow decay up to ~2 d after the burst, which is not consistent with standard afterglow models. The most intriguing feature is a very steep decay in the X-ray flux at ~20 ks after the burst, ending an apparent plateau. The abrupt drop of the X-ray light curve rules out an external shock as the origin of the plateau in this burst and implies long-lasting activity of the central engine. The temporal and s…

XMM‐NewtonObservations of the Supernova Remnant IC 443. I. Soft X‐Ray Emission from Shocked Interstellar Medium

The shocked interstellar medium around IC443 produces strong X-ray emission in the soft energy band (E<1.5 keV). We present an analysis of such emission as observed with the EPIC MOS cameras on board the XMM-Newotn observatory, with the purpose to find clear signatures of the interactions with the interstellar medium (ISM) in the X-ray band, which may complement results obtained in other wavelenghts. We found that the giant molecular cloud mapped in CO emission is located in the foreground and gives an evident signature in the absorption of X-rays. This cloud may have a torus shape and the part of torus interacting with the IC443 shock gives rise to 2MASS-K emission in the southeast. The…

New constraints on chemical abundances of the shocked plasma in the supernova remnant IC443

XMM-Newton observations of the supernova remnant IC 443: II. evidence of stellar ejecta in the inner regions

We investigate the spatial distribution of the physical and chemical properties of the hot X-ray emitting plasma of the supernova remnant IC 443, in order to get important constraints on its ionization stage, on the progenitor supernova explosion, on the age of the remnant, and its physical association with a close pulsar wind nebula. The hard X-ray thermal emission (1.4-5.0 keV) of IC 443 displays a centrally-peaked morphology, its brightness peaks being associated with hot (kT>1 keV) X-ray emitting plasma. A ring-shaped structure, characterized by high values of equivalent widths and median photon energy, encloses the PWN. Its hard X-ray emission is spectrally characterized by a collis…

The THESEUS space mission concept: science case, design and expected performances

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5¿1 arcmin localization, an energy band extending from several MeV down to 0.3¿keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7¿m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing …

GRB 061121: Broadband Spectral Evolution through the Prompt and Afterglow Phases of a Bright Burst

Swift triggered on a precursor to the main burst of GRB 061121 (z=1.314), allowing observations to be made from the optical to gamma-ray bands. Many other telescopes, including Konus-Wind, XMM-Newton, ROTSE and the Faulkes Telescope North, also observed the burst. The gamma-ray, X-ray and UV/optical emission all showed a peak ~75s after the trigger, although the optical and X-ray afterglow components also appear early on - before, or during, the main peak. Spectral evolution was seen throughout the burst, with the prompt emission showing a clear positive correlation between brightness and hardness. The Spectral Energy Distribution (SED) of the prompt emission, stretching from 1eV up to 1MeV…