Swift gamma-ray bursts—a 3D step toward standard candles

Swift gamma-ray bursts—a 3D step toward standard candles
A typical long (> 2 s) duration Gamma-Ray Burst that shows the peak luminosity, the plateau luminosity and the time at plateau end. The combination of these three parameters were found to work the best as distance indicators. Credit: NASA

A new way to use the most powerful explosions in the Universe to calibrate its expansion has been developed by a team of researchers (Sergey Postnikov, Xavier Hernandez from Institute of Astronomy , UNAM, and Michal Ostrowski from the Astronomical Observatory of Jagiellonian University) led by Marie Curie Outgoing Fellow at Stanford University, Maria Dainotti. Dainotti recently presented the results of her team's work at a press conference at the 228th meeting of the American Astronomical Society. Dainotti's three-dimensional analysis shows that a specific population of gamma-ray bursts can be used to provide an independent measurement of the cosmic distance scale. Since gamma-ray bursts are even brighter than supernovae, this new technique has the potential to extend the cosmic ruler to greater distances than are currently possible.

Astronomers refer to these cosmic rulers as "standard candles" - objects with a known intrinsic luminosity. Once the absolute luminosity is known, the distance to that object can be calculated based on its measured brightness. For example, a 100 Watt lightbulb will appear four times dimmer when it is twice as far away.

"This 3D correlation, since it is the tightest among the prompt-afterglow ones so far in the literature, will offer the opportunity to estimate the cosmological parameters and then allows a direct investigation of the cosmological evolution of the Universe up to epoch of reionization", said Dr. Dainotti.

Although supernova explosions are very bright, the useful range over which they can be used as standard candles extends out only to distances of around 11 billion light years (redshifts up to 2.4). In contrast, GRBs can be studied out to distances of 13.2 billion light years (redshifts as great as 9.4). Studying the very early Universe is critical to understanding the details of cosmological evolution; e.g., the characteristics of dark energy from the epoch of reionization to the present.

Swift gamma-ray bursts—a 3D step toward standard candles
The three-dimensional correlation between peak luminosity (Lpeak), plateau luminosity (La) and time the plateau ends (Ta) demonstrating the tight correlation obtained using the combination of these three parameters. The observed luminosities have been converted into absolute luminosities using distances derived from redshift measurements of the afterglow emission. Credit: NASA

Many previous studies have attempted to use different features of the light emitted by GRBs to define standard candles. However, even when all the GRBs are observed in a uniform manner with, e.g., NASA's Swift satellite, these features are seen to vary widely over orders of magnitude. This applies not only to the prompt emission (the main event in the gamma rays), but also to the extended afterglow phase (which follows the prompt emission and is seen over a range of wavelengths as the embers from the explosion cool). To complicate matters further, no single clear explanation as to the physical nature of GRBs exists. Possible causes range from the collapse of massive stars, to magnetars in the process of spinning down, to the collapse of supernovae, to binary mergers.

Over the past decade, many efforts have been made to find correlations between characteristic parameters that can be measured using GRBs. Previous efforts looked for relationships among pairs of parameters. Dainotti's idea was to introduce a third parameter to tighten the correlation and increase the utility of GRBs as . This proved to reduce the scatter in the data points within the group of long GRBs (duration greater than 2 s). The parameters that Dainotti found worked the best to provide accurate distance indicators were the observed luminosity at the GRB peak, the time that the afterglow plateau end and the luminosity during the afterglow. These results were verified by using Monte Carlo simulations to prove that the 3D correlation was not a random effect due to the GRBs that were used in the analysis.


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More information: The paper 'A fundamental plane for gamma-ray bursts with X-ray plateaus' by Dainotti, M. G., Postnikov, S., Hernandez, X., & Ostrowski, M. has been accepted for publication in the Astrophysical Journal, Letters. The preprint can be downloaded from: arxiv.org/abs/1604.06840
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Citation: Swift gamma-ray bursts—a 3D step toward standard candles (2016, June 21) retrieved 20 June 2019 from https://phys.org/news/2016-06-swift-gamma-ray-burstsa-3d-standard.html
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Jun 21, 2016
Dainotti's idea was to introduce a third parameter to tighten the correlation and increase the utility of GRBs as standard candles. This proved to reduce the scatter in the data points within the group of long GRBs (duration greater than 2 s).
Very good idea. So in addition to the "end time of the plateau, T_a, and its corresponding x-ray luminosity, L_a," parameters, the introduced third parameter is the "peak luminosity in the prompt emission, L_peak."

It looks like it was also helpful to restrict the sample of GRBs by "excluding GRBs with associated Supernovae (SNe), X-ray flashes and short GRBs with extended emission," (thereby defining a unique class of GRBs).

It worked out quite well – can't wait to discover the source of this class, am guessing the merger of a stellar-mass black hole with a neutron star is a pretty good candidate. The paper mentions it's possibly the birth of a rapidly spinning millisecond pulsar, or accretion onto a black hole.

Jun 22, 2016
Sub: Necessity-Search Origins-cosmology Vedas Interlinks
1.Since gamma-ray bursts are even brighter than supernovae
2.supernovae 11 billion light years (redshifts up to 2.4). GRBs studied out to distances of 13.2 B LY
comments: search Cosmic function of the Universe, cosmological structures, cosmic Pot Energy of the universe-expect 240 Cosmic pots
think Tanks-cosmic Function of the Universe
The Concept of Big-Bang needs revision and Paradigm shift.
The Origins- Cause effect define Cosmic Pot Energy of the Universe- research paper presented by me at STSCI-May 2003 symposium.see Cosmology Structures new Modelling-Carnegie 2003
www [dot]scribd [dot]com-doc-21526401-Cosmic-Pot-Universe-2003
cosmology vedas interlinks- 15 Books available at LULU

Jun 22, 2016
Hi Protoplasmix. :)

Glad to see you are noticing astronomical discoveries of late, vindicating my longstanding cautions re both 'standard candle' and 'distance ladder' assumptions, techniques and interpretations; which mainstream cosmologists have treated/offered as 'observational support' for past claims re Big Bang, Distance-Expansion-Rate etc theory/hypothesis/model etc.

See now? There is HUGE range/variety in luminous radiation events, determined by 'local' conditions, materials, dynamics. Any one of the large numbers of distant 'E-M burst' events could have 'mimicked' a 'standard candle' model candidate in Saul Perlmutters' survey.

We now realize we CANNOT AS YET KNOW EXACTLY WHAT a distant 'burst' is representing LOCALLY; so we cannot still assume naively that we can tell from HERE whether observed 'E-M burst event' is a 'standard candle' model example or a MIMIC of such; hence we cannot depend on naive distance/redshift/luminosity techniques/associations/claims. :)

Jun 26, 2016
See now?
I see what the scientists are saying, most of the time, as they are good at communicating their point in a logical, straightforward manner with well defined terms and well referenced formulations. And after some extra effort at teasing meaning from vague mumbo-jumbo, I see your point too. Hopefully it makes sense to you that it's easy to see which points are hard to dismiss without more data from additional observations, and which points are easily dismissed as anti-science ill-informed hand waving.

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