Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Two cosmic bursts upset tidy association between long gamma-ray bursts and supernovae

22.12.2006
Newfound diversity in gamma-ray bursts puzzles astronomers

Two brilliant flashes of light from nearby galaxies are puzzling astronomers and could indicate that gamma-ray bursts, which signal the birth of a black hole, are more diverse than once thought.

First seen 40 years ago, gamma-ray bursts are the brightest explosions in the universe. They appear to fall into two distinct categories, short and long, depending on whether they shine for less than or more than about two seconds. Observations accumulated over the last decade led to a consensus that the long variety occurred when a massive star at the end of its life collapses to form a black hole. In addition to making a burst of gamma-rays, the explosion also produces a bright supernova. The short ones, not accompanied by a supernova, are thought to herald the merger of two neutron stars or a neutron star and a black hole, resulting in a bigger black hole.

The two new gamma-ray bursts are of the long variety but, surprisingly, did not show any evidence of supernova activity. This flies in the face of what was an emerging consensus about the origin of long bursts, according to University of California, Berkeley's Joshua Bloom, assistant professor of astronomy. To Bloom, this indicates that there are more than two ways to produce a gamma-ray flash and a black hole.

"Instead of simplicity and clarity, we're seeing a rich diversity emerge - there are more ways than we thought for producing flashes of gamma-rays," Bloom said.

Bloom and 30 colleagues from around the world report observations of two of these peculiar gamma-ray bursts, labeled GRB 060505 and GRB 060614, in the Dec. 21 issue of the British journal Nature. Three other papers in the same issue report details of GRB 060614. Both bursts were detected by NASA's Swift satellite - the first on May 5, 2006, the second on June 14, 2006.

Based solely on GRB 060614, many astronomers remained skeptical about the need to cast away the tidy connection of long bursts to supernovae. Yet, as Bloom stated, "It's easy to explain away one of these anomalous events as a fluke, but two strange events give our claim some oomph. These events are observational threats to the one-to-one association between long bursts and supernovae."

The whole story started with a non-discovery. Daniel Perley, a graduate student in astronomy at UC Berkeley, suggested that he and Bloom use the W. M. Keck Telescope in Hawaii to observe an area of sky where the long burst GRB 060505 had been seen in May. That long burst lasted four seconds and was pinpointed inside a galaxy a little over 1 billion light years away, towards the constellation Piscis Austrinus.

Had this flash been associated with the kind of supernova typically seen at sites of long gamma-ray bursts, or even a relatively weak supernova down to 250 times less powerful, Keck would have detected it, but instead Bloom and Perley observed nothing but the parent galaxy.

"We usually learn a lot about an event when new sources are detected, but in this context, it was much more exciting to detect nothing," Perley said.

At around the same time, a Danish group headed by Johan Peter Uldall Fynbo of the Neils Bohr Institute at the University of Copenhagen had had similar lack of success finding a supernova associated with GRB 060614. That burst lasted almost two minutes and was pinpointed near a galaxy 1.6 billion light years away, towards the constellation Indus. In both cases, the presence of obscuring dust was ruled out.

Fynbo gathered data from an international team, including Bloom and Perley, which argued in the Nature paper that the two supernovae together suggest a "new phenomenological type of massive stellar death."

Most astronomers have concluded that some new process must be at play: either the model of mergers creating second-long "short" bursts needs a major overhaul, or the progenitor star from this peculiar explosion is intrinsically different from the kind that make supernovae and long bursts.

"The paradigm had emerged that all long bursts were associated with the death of massive stars," said Bloom, who last year discovered evidence that convincingly linked short-lived gamma-ray bursts to the explosive merger of old, dead stars. The new observations "do not rule out a massive star origin, but does require that supernovae produced in some explosions are either very weak or non-existent."

Swift, launched in November 2004, is a NASA mission managed by NASA Goddard in partnership with the Italian Space Agency and the Particle Physics and Astronomy Research Council of the United Kingdom.

Robert Sanders | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Physics and Astronomy:

nachricht Four elements make 2-D optical platform
26.09.2017 | Rice University

nachricht The material that obscures supermassive black holes
26.09.2017 | Instituto de Astrofísica de Canarias (IAC)

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The fastest light-driven current source

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

Graphene is up to the job

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Nerves control the body’s bacterial community

26.09.2017 | Life Sciences

Four elements make 2-D optical platform

26.09.2017 | Physics and Astronomy

Goodbye, login. Hello, heart scan

26.09.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>