Systematic study for gas-to-dust ratio of short gamma-ray burst afterglows. (arXiv:1903.05963v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yoshida_K/0/1/0/all/0/1">Kazuki Yoshida</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yonetoku_D/0/1/0/all/0/1">Daisuke Yonetoku</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arimoto_M/0/1/0/all/0/1">Makoto Arimoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sawano_T/0/1/0/all/0/1">Tatsuya Sawano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kagawa_Y/0/1/0/all/0/1">Yasuaki Kagawa</a>

Extra-galactic X-ray absorption and optical extinction are often found in
gamma-ray burst (GRB) afterglows and they could be tracers of both circumburst
and host galaxy environments. By performing spectral analyses for spectral
energy distribution of 9 short GRB (SGRB) afterglows with known redshift, we
investigated a ratio of the equivalent hydrogen column density to the dust
extinction, N^{rest}_{H}/A^{rest}_{V}, in the rest frame of each SGRB. We found
that the distribution of N^{rest}_{H}/A^{rest}_{V} is systematically smaller
than the one for long GRBs, and is roughly consistent with the gas-to-dust
ratio in the Milky Way. This result means that the measured gas-to-dust ratio
of SGRBs would originate from the interstellar medium in each host galaxy. This
scenario supports the prediction that SGRBs occur in non star-forming regions
in the host galaxies.

Extra-galactic X-ray absorption and optical extinction are often found in
gamma-ray burst (GRB) afterglows and they could be tracers of both circumburst
and host galaxy environments. By performing spectral analyses for spectral
energy distribution of 9 short GRB (SGRB) afterglows with known redshift, we
investigated a ratio of the equivalent hydrogen column density to the dust
extinction, N^{rest}_{H}/A^{rest}_{V}, in the rest frame of each SGRB. We found
that the distribution of N^{rest}_{H}/A^{rest}_{V} is systematically smaller
than the one for long GRBs, and is roughly consistent with the gas-to-dust
ratio in the Milky Way. This result means that the measured gas-to-dust ratio
of SGRBs would originate from the interstellar medium in each host galaxy. This
scenario supports the prediction that SGRBs occur in non star-forming regions
in the host galaxies.

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