Change search
ReferencesLink to record
Permanent link

Direct link
Evidence for a photospheric component in the prompt emission of the short grb 120323a and its effects on the grb hardness-luminosity relation
Show others and affiliations
2013 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 770, no 1, 32- p.Article in journal (Refereed) Published
Abstract [en]

The short GRB 120323A had the highest flux ever detected with the Gamma-Ray Burst Monitor on board the Fermi Gamma-Ray Space Telescope. Here we study its remarkable spectral properties and their evolution using two spectral models: (1) a single emission component scenario, where the spectrum is modeled by the empirical Band function (a broken power law), and (2) a two-component scenario, where thermal (a Planck-like function) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the E peak of the event is unusually soft for a short gamma-ray burst (GRB; 70 keV compared to an average of 300 keV), while adding a thermal component leads to more typical short GRB values (E peak 300 keV). Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A based on (1) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (2) the appearance in the data of a significant hardness-intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, observed for the first time in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness-luminosity relation in the source frame using a larger set of GRBs (), which could be used as a possible redshift estimator for cosmology.

Place, publisher, year, edition, pages
2013. Vol. 770, no 1, 32- p.
Keyword [en]
acceleration of particles, cosmology: miscellaneous, gamma rays: stars, gamma-ray burst: individual (GRB 120323A), radiation mechanisms: non-thermal, radiation mechanisms: thermal
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-134255DOI: 10.1088/0004-637X/770/1/32ISI: 000319986400032ScopusID: 2-s2.0-84878274451OAI: diva2:665964

QC 20131121

Available from: 2013-11-21 Created: 2013-11-20 Last updated: 2013-12-10Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Ryde, Felix
By organisation
Particle and Astroparticle Physics
In the same journal
Astrophysical Journal
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 22 hits
ReferencesLink to record
Permanent link

Direct link