GRB 070714B—DISCOVERY OF THE HIGHEST SPECTROSCOPICALLY CONFIRMED SHORT BURST REDSHIFT
GRB 070714B—DISCOVERY OF THE HIGHEST SPECTROSCOPICALLY CONFIRMED SHORT BURST REDSHIFT
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DOI：
10.1088/0004-637x/698/2/1620
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
J. Graham;A. Fruchter;A. Levan;A. Melandri;L. Kewley;E. Levesque;M. Nysewander;N. Tanvir;T. Dahlén;D. Bersier;K. Wiersema;D. Bonfield;A. Martínez-Sansigre
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作者：
J. Graham;A. Fruchter;A. Levan;A. Melandri;L. Kewley;E. Levesque;M. Nysewander;N. Tanvir;T. Dahlén;D. Bersier;K. Wiersema;D. Bonfield;A. Martínez-Sansigre
我们观测到GRB 070714 B的光学余辉和宿主星系。我们对余辉的观测表明，在大约最初的5-25分钟内，光变曲线上有一个初始平台，然后在爆发后1 - 24小时内变陡，达到指数α = 0.86 ± 0.10的幂律衰减。这与X射线光变曲线一致，其显示初始平台，随后是类似的随后衰减。在晚些时候，我们在光学瞬变的位置检测到一个宿主星系。双子座Nod & Shuffle光谱观测主机显示一个单一的发射线在7167 <$A，根据格里兹JHK光度红移，我们得出结论是3727 <$A [O ii]线。因此，我们发现红移z = 0.923。这一红移，以及随后由另外两个小组在z = 0.904处对GRB 070429 B的光谱红移的测定，明显超过了GRB 051221之前光谱确认的最高短爆发红移z = 0.546。这大大地将我们所知道的短爆发形成的时间向后移动，并表明目前关于古老祖先种群的证据可能在观测上有偏差。
We detect the optical afterglow and host galaxy of GRB 070714B. Our observations of the afterglow show an initial plateau in the light curve for approximately the first 5–25 minutes, and then steepening to a power-law decay with index α = 0.86 ± 0.10 for the period between 1 and 24 hr postburst. This is consistent with the X-ray light curve which shows an initial plateau followed by a similar subsequent decay. At late time, we detect a host galaxy at the location of the optical transient. Gemini Nod & Shuffle spectroscopic observations of the host show a single emission line at 7167 Å which, based on a griz JHK photometric redshift, we conclude is the 3727 Å [O ii] line. We therefore find a redshift of z = 0.923. This redshift, as well as a subsequent probable spectroscopic redshift determination of GRB 070429B at z = 0.904 by two other groups significantly exceeds the previous highest spectroscopically confirmed short burst redshift of z = 0.546 for GRB 051221. This dramatically moves back the time at which we know short bursts were being formed and suggests that the present evidence for an old progenitor population may be observationally biased.