Title: GRB 130603B: No Compelling Evidence For Neutron Star Merger Author: Shlomo Dado, Arnon Dar
Near infrared (NIR) flare/rebrightening in the afterglow of the short hard gamma ray burst (SHB) 130603B measured with the Hubble Space Telescope (HST) and an alleged late-time X-ray excess were interpreted as possible evidence of a neutron-star merger origin of this SHB. However, the X-ray afterglow that was measured with the Swift-XRT and Newton XMM have the canonical behaviour of a synchrotron afterglow produced by a highly relativistic jet. The H-band flux observed with HST 9.41 days after burst is that expected from the measured late-time X-ray afterglow. A late-time flare/re-brightening of a NIR-Optical afterglow of SHB can be produced by jet collision with an interstellar density bump, or by a kilonova, but jet plus kilonova can be produced also by the collapse of compact stars (neutron star, strange star, or quark star) to a more compact object due to cooling, loss of angular momentum, or mass accretion.
Ever since U.S. Air Force satellites serendipitously discovered gamma-ray bursts in the 1960s, astronomers have been searching for the triggering mechanism. Gamma-ray bursts are mysterious flashes of intense high-energy radiation that appear from random directions in space. These titanic explosions unleash as much energy in less than a second as the Sun does in 1 million years. Now, astronomers are using NASA's Hubble Space Telescope to gather key evidence on what powers short-duration gamma-ray bursts, which last up to two seconds. Probing the location of a recent short-duration burst in near-infrared light, Hubble found the fading fireball produced in the aftermath of the blast. The afterglow reveals for the first time a new kind of stellar blast called a kilonova, an explosion predicted to accompany a short-duration gamma-ray burst. The kilonova is the "smoking gun" evidence that short-duration bursts are sparked by the merger of two small, super-dense stellar objects, such as a pair of neutron stars or a neutron star and a black hole. Read more