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Post Info TOPIC: Wolf-Rayet/black-hole binary
Blobrana


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Supernova 2006jc
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Title: SN 2006jc: A Wolf-Rayet Star Exploding in a Dense He-Rich Circumstellar Medium
Authors: Ryan J. Foley, Nathan Smith, Mohan Ganeshalingam, Weidong Li, Ryan Chornock, Alexei V. Filippenko

We present optical photometry and spectra of the peculiar type Ib supernova (SN) 2006jc. Strong He I emission lines indicate the progenitor star exploded inside a dense circumstellar medium (CSM) rich in He. An exceptionally blue continuum persists from our first spectrum obtained 15 days after discovery through our last spectrum ~1 month later. Based on the presence of isolated Fe II emission lines, we interpret the blue continuum as fluorescent Fe emission, although we do not understand the cause of this unusual fluorescence. The red He I line profiles are double peaked, suggesting that the CSM has a highly aspherical geometry. The He I lines that are superposed on the blue continuum show P-Cygni profiles, while the redder He I lines do not, implying that the blue continuum is related to the aspherical geometry. The He-rich CSM, aspherical geometry, and a recent coincident luminous outburst indicate that the progenitor star was a WNE Wolf-Rayet (WR) star, possibly transitioning from the luminous blue variable stage. We also present unpublished spectral and photometric data of SN 2002ao, which along with SN 1999cq, is very similar to SN 2006jc. We propose these three objects may represent a new and distinct class of SNe with dense environments around WR stars.

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Blobrana


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RE: Wolf-Rayet/black-hole binary
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Title: Massive binaries, Wolf-Rayet stars and supernova progenitors
Authors: J.J. Eldridge

Binary stars are important for a full understanding of stellar evolution. We present a summary of how predictions of the relative supernova rates varies between single and binary stars. We also show how the parameter space of different supernova types differs between single and binary stars. We then consider an important question of how to infer a supernova progenitor's properties from pre-explosion imaging and present recent work of producing synthetic colours for our stellar models to make a direct comparison with any detections or limits obtained on supernova progenitors from pre-explosion images.

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Blobrana


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Posts: 131433
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Title: A Wolf-Rayet/black-hole X-ray binary candidate in NGC 300
Authors: S. Carpano, A.M.T. Pollock, J. Wilms, M. Ehle, M. Schirmer

Wolf Rayet/black hole binaries are believed to exist as a later evolutionary product of high-mass X-ray binaries. Hundreds of such binaries may exist in galaxies, but only a few of them are close enough to be observed as X-ray binaries. Only a couple of candidates have been reported so far. Aims. Based on XMM-Newton observations, we report the positional coincidence of the brightest X-ray source in NGC 300 (NGC 300 X-1) with a Wolf-Rayet candidate. Temporal and spectral analysis of the X-ray source is performed. Methods. We determine an accurate X-ray position of the object, and derive light curves, spectra and flux in four XMM-Newton observations. Results. The positions of the X-ray source and the helium star candidate coincide within 0.11"+-0.45". The X-ray light curves show irregular variability. During one XMM-Newton observation, the flux increased by about a factor of ten in 10 hours. The spectrum can be modelled by a power-law with Gamma~2.45 with additional relatively weak line emission, notably around 0.95 kev. The mean observed (absorbed) luminosity in the 0.2-10 kev band is ~2x10^38 erg/s. Conclusions. NGC 300 X-1 is a good candidate for a Wolf-Rayet/black-hole X-ray binary: its position coincides with a Wolf-Rayet candidate and the unabsorbed X-ray luminosity reached L(0.2-10 kev)~1x10^39 erg/s, suggesting the presence of a black hole.

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