Pulsars, transients and relativistic astrophysics

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A giant outburst two years before the core-collapse of a massive star.

Nature 447:7146 (2007) 829-832

Authors:

A Pastorello, SJ Smartt, S Mattila, JJ Eldridge, D Young, K Itagaki, H Yamaoka, H Navasardyan, S Valenti, F Patat, I Agnoletto, T Augusteijn, S Benetti, E Cappellaro, T Boles, J-M Bonnet-Bidaud, MT Botticella, F Bufano, C Cao, J Deng, M Dennefeld, N Elias-Rosa, A Harutyunyan, FP Keenan, T Iijima, V Lorenzi, PA Mazzali, X Meng, S Nakano, TB Nielsen, JV Smoker, V Stanishev, M Turatto, D Xu, L Zampieri

Abstract:

The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf-Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet star exploding as SN 2006jc, could explain the observations.
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The variable radio-to-X-ray spectrum of the magnetar XTE J1810-197

ArXiv 0705.4095 (2007)

Authors:

F Camilo, SM Ransom, J Penalver, A Karastergiou, MH van Kerkwijk, M Durant, JP Halpern, J Reynolds, C Thum, DJ Helfand, N Zimmerman, I Cognard

Abstract:

We have observed the 5.54s anomalous X-ray pulsar XTE J1810-197 at radio, millimeter, and infrared (IR) wavelengths, with the aim of learning about its broad-band spectrum. At the IRAM 30m telescope, we have detected the magnetar at 88 and 144GHz, the highest radio-frequency emission ever seen from a pulsar. At 88GHz we detected numerous individual pulses, with typical widths ~2ms and peak flux densities up to 45Jy. Together with nearly contemporaneous observations with the Parkes, Nancay, and Green Bank telescopes, we find that in late 2006 July the spectral index of the pulsar was -0.5
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Evidence for a jet contribution to the optical/infrared light of neutron star X-ray binaries

(2007)

Authors:

DM Russell, RP Fender, PG Jonker
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SN 1996cr: Confirmation of a Luminous Type IIn Supernova in the Circinus Galaxy

(2007)

Authors:

FE Bauer, S Smartt, S Immler, WN Brandt, KW Weiler
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The luminous X-ray hotspot in 4C 74.26: synchrotron or inverse-Compton emission?

ArXiv 0705.1339 (2007)

Authors:

MC Erlund, AC Fabian, Katherine M Blundell, C Moss, DR Ballantyne

Abstract:

We report the discovery of an X-ray counterpart to the southern radio hotspot of the largest-known radio quasar 4C 74.26 (whose redshift is z=0.104). Both XMM-Newton and Chandra images reveal the same significant (10arcsec, i.e. 19kpc) offset between the X-ray hotspot and the radio hotspot imaged with MERLIN. The peak of the X-ray emission may be due to synchrotron or inverse-Compton emission. If synchrotron emission, the hotspot represents the site of particle acceleration and the offset arises from either the jet exhibiting Scheuer's `dentist's drill' effect or a fast spine having less momentum than the sheath surrounding it, which creates the radio hotspot. If the emission arises from the inverse-Compton process, it must be inverse-Compton scattering of the CMB in a decelerating relativistic flow, implying that the jet is relativistic (Gamma >= 2) out to a distance of at least 800kpc. Our analysis, including optical data from the Liverpool Telescope, rules out a background AGN for the X-ray emission and confirms its nature as a hotspot, making it the most X-ray luminous hotspot yet detected.
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