Monday, Feb. 11, 2013

I think we should look at the "Very Massive Stars" discussion. It’s very long, but they are going over the recent claim of 300M_sun stars in the local universe, how to diagnose their properties if they exist.

Variable dust formation by the colliding-wind Wolf-Rayet system HD 36402 in the Large Magellanic Cloud P. M. Williams (1), Y.-H. Chu (2), R. A. Gruendl (2), M. A. Guerrero (3) ((1) Institute for Astronomy, Royal Observatory, Edinburgh, (2) Department of Astronomy, University of Illinois at Urbana-Champaign, (3) Instituto de Astrofisica de Andalucia, Granada) (Submitted on 8 Feb 2013)

Infrared photometry of the probable triple WC4(+O?)+O8I: Wolf-Rayet system HD 36402 (= BAT99-38) in the Large Magellanic Cloud (LMC) shows emission characteristic of heated dust. The dust emission is variable on a time-scale of years, with a period near 4.7 yr, possibly associated with orbital motion of the O8 supergiant and the inner P ~ 3.03-d WC4+O binary. The phase of maximum dust emission is close to that of the X-ray minimum, consistent with both processes being tied to colliding wind effects in an elliptical binary orbit. It is evident that Wolf-Rayet dust formation occurs also in metal-poor environments.

Comments: 8 pages, 4 figures, to be published in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1302.2002 [astro-ph.SR]
(or arXiv:1302.2002v1 [astro-ph.SR] for this version)

Very Massive Stars (VMS) in the Local Universe Jorick S. Vink, Alexander Heger, Mark R. Krumholz, Joachim Puls (and the participants of Joint Discussion 2 IAU-GA) (Submitted on 8 Feb 2013)

Recent studies have claimed the existence of very massive stars (VMS) up to 300 solar masses in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 Msun, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.

Comments: 29 pages, 7 figures, Proceedings Joint Discussion 2. To be published in Hightlights of Astronomy, ed. T. Montmerle
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:1302.2021 [astro-ph.SR]
(or arXiv:1302.2021v1 [astro-ph.SR] for this version)

AGN and star formation activity in local luminous and ultraluminous infrared galaxies Almudena Alonso-Herrero (Submitted on 8 Feb 2013)

The enormous amounts of infrared (IR) radiation emitted by luminous infrared galaxies (LIRGs, L_IR=10^11-10^12Lsun) and ultraluminous infrared galaxies (ULIRGs, L_IR>10^12Lsun) are produced by dust heated by intense star formation (SF) activity and/or an active galactic nucleus (AGN). The elevated star formation rates and high AGN incidence in (U)LIRGs make them ideal candidates to study the interplay between SF and AGN activity in the local universe. In this paper I review recent results on the physical extent of the SF activity, the AGN detection rate (including buried AGN), the AGN bolometric contribution to the luminosity of the systems, as well as the evolution of local LIRGs and ULIRGs. The main emphasis of this review is on recent results from IR observations.

Comments: Invited review at "Nuclei of Seyfert galaxies and QSOs – Central engine & conditions of star formation" to appear in Proceedings of Science
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1302.2033 [astro-ph.CO]
(or arXiv:1302.2033v1 [astro-ph.CO] for this version)
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