[Triumf-seminars] TRIUMF Seminar today at 14:00

[postmaster at admin.triumf.ca]

Date/Time: Thu 2009-08-06 at 14:00

Location:  Auditorium          

Speaker:   Rachid Ouyed (University of Calgary)

Title:     Astrophysical signatures of hadronic-to-quark-matter phase  transitions

Abstract: Supernova explosions of massive stars are generally thought to leave behind either a black hole or a neutron star. However, allowing for a quark star phase (i.e. a Quark-Nova explosion) leads to a dual-shock phenomena (the SN shock followed by the Quark-Nova, hereafter QN, shock) with interesting astrophysical implications. In particular I will focus on recent phenomena making a case for dual-shock QNe having manifested themselves as: (i) Extremely Super-luminous Supernovae (or hyper-novae). For Quark-Novae that arise days after the SNe, I will show that the collision between the QN ejecta and the SN ejecta can produce enough photons to give excellent fits to super-luminous SNe lightcurves (such as SN 2006gy); The same model is used to fit the bumps seen in X-ray flares of Gamma Ray Bursts (GRB) suggesting that these dual-shock explosions may be behind the still elusive GRB phenomenon; (ii) Re-ionization sources. Here I describe the case for QNe as possible sources for the re-ionization and early metal enrichment of the universe. Dual-shock QNe linked to the first (i.e. Population III) stars can produce enough photons to reionize hydrogen in most of the Inter-Galactic medium (IGM) by z ~ 6. Most importantly, with QNe a normal initial mass function (IMF) for the oldest stars can be reconciled with a large optical depth (determined by WMAP) as well as the mean metallicity of the early IGM post re-ionization. 

A tell-tale signature that would clearly distinguish a QN from a SN would be the detection of radioactive elements with lifetimes of order several days or few weeks. Such short-lived elements cannot realistically be detected in SN, since their decay times are too short compared to the gamma transparency of the SN ejecta. But the QN ejecta is relativistic and plows into the SN ejecta at very large speeds. If subsequent mixing effects are strong, there is the possibility that some of the short-lived heavy elements could be detected against the background of the late-time (decaying) light curve (what seems to have happened in SN2006gy). We have identified the following “signature” elements of the QN/dsQN (All of them are gamma-active with lifetimes of few days-few weeks): 143Pr, 156Eu, 161Tb, 166Dy, 169Er, 175Yb , 177Lu, 183Ta, 191Os, 193Ir, 210Bi, 223Ra , 225Ac, 233Pa.

Stimulants available 15 minutes before the talk.

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