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Metallicity Measurements of Gamma-Ray Burst and Supernova Explosion Sites: Lessons from HII regions in M31. (arXiv:1408.7059v2 [astro-ph.HE] UPDATED)

February 27th, 2015

Yuu Niino, Kentaro Nagamine, Bing Zhang

We examine how the small-scale ($<$\,kpc) variation of metallicity within a
galaxy, which is found in nearby galaxies, affect the observational estimates
of metallicity in the explosion sites of transient events such as core-collapse
supernovae (CC SNe) and gamma-ray bursts (GRBs). Assuming the same luminosity,
metallicity, and spatial distributions of \ion{H}{ii}\ regions (hereafter
HIIRs) as observed in M31, we compute the apparent metallicities that we would
obtain when the spectrum of a target region is blended with those of
surrounding HIIRs within the length scale of typical spatial resolution. When
the spatial resolution of spectroscopy is $\lesssim$ 0.5\,kpc, which is typical
for the existing studies of CC SN sites, we find that the apparent
metallicities reflect the metallicities of target regions, but with significant
systematic uncertainties in some cases. When the spatial resolution is
$\gtrsim$ 1.0 kpc, regardless of the target regions (which has a wide range of
metallicity that spans $\sim$ 0.6 dex for the M31 HIIRs), we always obtain the
apparent metallicities similar to the average metallicity of the M31 HIIRs.
Given that the apparent metallicities measured with $\gtrsim$\,kpc scale
resolution do not necessarily reflect the immediate environment of the stellar
explosions, the current observational estimates of high metallicities for some
of the long GRB host galaxies do {\em not} rule out the hypothesis that the
long GRBs are exclusively born in a low-metallicity environment.


http://arxiv.org/abs/1408.7059


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Search for gamma-rays from the unusually bright GRB 130427A with the HAWC Gamma-ray Observatory. (arXiv:1410.1536v2 [astro-ph.HE] UPDATED)

February 27th, 2015


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The Needle in the 100 deg2 Haystack: Uncovering Afterglows of Fermi GRBs with the Palomar Transient Factory. (arXiv:1501.00495v2 [astro-ph.HE] UPDATED)

February 27th, 2015


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Numerical Models of Blackbody-Dominated GRBs. (arXiv:1502.07134v1 [astro-ph.HE])

February 26th, 2015


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Structure of Gamma-Ray Burst jets: intrinsic versus apparent properties. (arXiv:1502.06608v2 [astro-ph.HE] UPDATED)

February 26th, 2015


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Structure of Gamma-Ray Burst jets: intrinsic versus apparent properties. (arXiv:1502.06608v1 [astro-ph.HE])

February 25th, 2015


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Selection effects in Gamma Ray Bursts correlations: consequences on the ratio between GRB and star formation rates. (arXiv:1412.3969v4 [astro-ph.HE] UPDATED)

February 24th, 2015


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Search for GeV Gamma Ray Bursts with the ARGO-YBJ Detector: Summary of Eight Years of Observations. (arXiv:1502.05622v1 [astro-ph.HE])

February 20th, 2015


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Relation between the intrinsic and observed central engine activity time: implications for ultra-long GRBs. (arXiv:1411.2650v2 [astro-ph.HE] UPDATED)

February 20th, 2015


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Temporal properties of bright BGO GRBs detected by Fermi. (arXiv:1502.04714v1 [astro-ph.HE])

February 18th, 2015


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