Outliers from the mainstream: how a massive star can produce a gamma-ray burst

S. Campana$^1$, N. Panagia$^{2,3,4}$, D. Lazzati$^5$, A.P. Beardmore$^6$, G. Cusumano$^7$, O. Godet$^6$, G. Chincarini$^{8,1}$, S. Covino$^1$,
M. Della Valle$^{9,10,11}$, C. Guidorzi$^{8,1}$, D. Malesani$^{12}$, A. Moretti$^1$, R. Perna$^5$, P. Romano$^{8,1}$, and G. Tagliaferri$^1$

1 - INAF–Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate
(LC), Italy; sergio.campana@brera.inaf.it.
2 - Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD
3 - INAF–Osservatorio Astrofisico di Catania, via S. Sofia 78, I-95123 Catania,
4 - Supernova Ltd., Olde Yard Village 131, Northsound Road, Virgin Gorda,
British Virgin Islands.
5 - JILA, Campus Box 440, University of Colorado, Boulder, CO 80309-0440.
6 - Department of Physics and Astronomy, University of Leicester, University
Road, Leicester LE1 7RH, UK.
7 - INAF–Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo, via U.
La Malfa 153, I-90146 Palermo, Italy.
8 - Universita` degli studi di Milano Bicocca, piazza delle Scienze 3, I-20126
Milano, Italy.
9 - European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748
Garching bei Mu¨nchen, Germany.
10 - INAF–Osservatorio Astronomico di Capodimonte, salita Moiariello 16,
I-80131 Napoli, Italy.
11 - International Center for Relativistic Astrophysics Network, Piazza della
Repubblica 10, I-65122, Pescara, Italy.
12 - Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen,
Juliane Maries vej 30, DK-2100 København Ø, Denmar

It is now recognized that long-duration gamma-ray Bursts (GRBs) are linked to the collapse of massive stars, based on the association between (low redshift) GRBs and (Type Ic) core-collapse supernovae (SNe). The census of massive stars and GRBs reveals, however, that not all massive stars produce a GRB. Only ∼1% of core-collapse SNe are able to produce a highly relativistic collimated outflow, and hence a GRB. The extra crucial parameter has long been suspected to be metallicity and/or rotation. We find observational evidence strongly supporting that both ingredients are necessary in order to make a GRB out of a core-collapsing star. A detailed study of the absorption pattern in the X-ray spectrum of GRB 060218 reveals evidence of material highly enriched in low-atomic-number metals ejected before the SN/GRB explosion. We find that, within the current scenarios of stellar evolution, only a progenitor star characterized by a fast stellar rotation and subsolar initial metallicity could produce such a metal enrichment in its close surrounding.

Reference: ApJ, 683: L9–L12
Status: Manuscript has been accepted

Weblink: http://babbage.sissa.it/abs/0805.4698


Email: sergio.campana@brera.inaf.it