Discovery of the optical afterglow and host galaxy of short GRB181123B at $z =1.754$: Implications for Delay Time Distributions. (arXiv:2007.03715v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Paterson_K/0/1/0/all/0/1">K. Paterson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fong_W/0/1/0/all/0/1">W. Fong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nugent_A/0/1/0/all/0/1">A. Nugent</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Escorial_A/0/1/0/all/0/1">A. Rouco Escorial</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leja_J/0/1/0/all/0/1">J. Leja</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Laskar_T/0/1/0/all/0/1">T. Laskar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chornock_R/0/1/0/all/0/1">R. Chornock</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miller_A/0/1/0/all/0/1">A. A. Miller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scharwachter_J/0/1/0/all/0/1">J. Scharwächter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cenko_S/0/1/0/all/0/1">S. B. Cenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perley_D/0/1/0/all/0/1">D. Perley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tanvir_N/0/1/0/all/0/1">N. R. Tanvir</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Levan_A/0/1/0/all/0/1">A. Levan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cucchiara_A/0/1/0/all/0/1">A. Cucchiara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cobb_B/0/1/0/all/0/1">B. E. Cobb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+De_K/0/1/0/all/0/1">K. De</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berger_E/0/1/0/all/0/1">E. Berger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Terreran_G/0/1/0/all/0/1">G. Terreran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alexander_K/0/1/0/all/0/1">K. D. Alexander</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nicholl_M/0/1/0/all/0/1">M. Nicholl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blanchard_P/0/1/0/all/0/1">P. K. Blanchard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cornish_D/0/1/0/all/0/1">D. Cornish</a>
We present the discovery of the optical afterglow and host galaxy of the {it
Swift} short-duration gamma-ray burst, GRB,181123B. Observations with
Gemini-North starting at $approx 9.1$~hr after the burst reveal a faint
optical afterglow with $iapprox25.1$~mag, at an angular offset of 0.59 $pm$
0.16$”$ from its host galaxy. Using $grizYJHK$ observations, we measure a
photometric redshift of the host galaxy of $z = 1.77^{+0.30}_{-0.17}$. From a
combination of Gemini and Keck spectroscopy of the host galaxy spanning
4500-18000~AA , we detect a single emission line at 13390~AA, inferred as
H$beta$ at $z = 1.754 pm 0.001$ and corroborating the photometric redshift.
The host galaxy properties of GRB,181123B are typical to those of other SGRB
hosts, with an inferred stellar mass of $approx 1.7 times
10^{10},M_{odot}$, mass-weighted age of $approx 0.9$~Gyr and optical
luminosity of $approx 0.9L^{*}$. At $z=1.754$, GRB,181123B is the most
distant secure SGRB with an optical afterglow detection, and one of only three
at $z>1.5$. Motivated by a growing number of high-$z$ SGRBs, we explore the
effects of a missing $z>1.5$ SGRB population among the current {it Swift}
sample on delay time distribution models. We find that log-normal models with
mean delay times of $approx 4-6$~Gyr are consistent with the observed
distribution, but can be ruled out to $95%$ confidence with an additional
$approx1-5$~{it Swift} SGRBs recovered at $z>1.5$. In contrast, power-law
models with $propto$ $t^{-1}$ are consistent with the redshift distribution
and can accommodate up to $approx30$ SGRBs at these redshifts. Under this
model, we predict that $approx 1/3$ of the current {it Swift} population of
SGRBs is at $z>1$. The future discovery or recovery of existing high-$z$ SGRBs
will provide significant discriminating power on their delay time
distributions, and thus their formation channels.
We present the discovery of the optical afterglow and host galaxy of the {it
Swift} short-duration gamma-ray burst, GRB,181123B. Observations with
Gemini-North starting at $approx 9.1$~hr after the burst reveal a faint
optical afterglow with $iapprox25.1$~mag, at an angular offset of 0.59 $pm$
0.16$”$ from its host galaxy. Using $grizYJHK$ observations, we measure a
photometric redshift of the host galaxy of $z = 1.77^{+0.30}_{-0.17}$. From a
combination of Gemini and Keck spectroscopy of the host galaxy spanning
4500-18000~AA , we detect a single emission line at 13390~AA, inferred as
H$beta$ at $z = 1.754 pm 0.001$ and corroborating the photometric redshift.
The host galaxy properties of GRB,181123B are typical to those of other SGRB
hosts, with an inferred stellar mass of $approx 1.7 times
10^{10},M_{odot}$, mass-weighted age of $approx 0.9$~Gyr and optical
luminosity of $approx 0.9L^{*}$. At $z=1.754$, GRB,181123B is the most
distant secure SGRB with an optical afterglow detection, and one of only three
at $z>1.5$. Motivated by a growing number of high-$z$ SGRBs, we explore the
effects of a missing $z>1.5$ SGRB population among the current {it Swift}
sample on delay time distribution models. We find that log-normal models with
mean delay times of $approx 4-6$~Gyr are consistent with the observed
distribution, but can be ruled out to $95%$ confidence with an additional
$approx1-5$~{it Swift} SGRBs recovered at $z>1.5$. In contrast, power-law
models with $propto$ $t^{-1}$ are consistent with the redshift distribution
and can accommodate up to $approx30$ SGRBs at these redshifts. Under this
model, we predict that $approx 1/3$ of the current {it Swift} population of
SGRBs is at $z>1$. The future discovery or recovery of existing high-$z$ SGRBs
will provide significant discriminating power on their delay time
distributions, and thus their formation channels.
http://arxiv.org/icons/sfx.gif
