NASA Astronomy Picture of the Day Collection

GRB 980703: A Reassuring Redshift

In the old days, just over a year ago, astronomers had little idea of the true distance to gamma-ray bursts [ http://antwrp.gsfc.…]. Did these enigmatic explosions [ http://www.sciam.co…] occur in our outer Galaxy [ http://adsbit.harva…], or in the outer Universe [ http://adsbit.harva…]? Last May, a first telling distance measure was made - GRB 970508 [ http://antwrp.gsfc.…] showed an absorption line [ http://antwrp.gsfc.…http://www.bc.kern.…] with a redshift [ http://antwrp.gsfc.…] of about 0.8 - indicating that this gamma-ray burst [ http://science.msfc…] (GRB) was an enormous distance away. Skeptics [ http://www.sff.net/…], however, are not always convinced by an unrepeated measurement. Since then, though, other tantalizing coincidences have occurred: GRB 971214 [ http://antwrp.gsfc.…] occurred unusually near a galaxy with the enormous redshift of 3.4, and GRB 980425 [ http://antwrp.gsfc.…] occurred unusually near a peculiar low-redshift supernova [ http://legacy.gsfc.…]. Skeptics [ http://www.athenet.…] were intrigued. Now, the potentially definitive implications of the above-pictured [ http://astro.caltec…] optical transient might impress even the cautious. GRB 980703 [ http://gcn.gsfc.nas…]'s optical transient shows a well-measured redshift from both an absorption line " and " an emission line [ http://astro.gmu.ed…]: 0.97. The above negative highlights the uncommon transient source with the label "OT", while letters designate common comparison stars [ http://gcn.gsfc.nas…].

S. G. Djorgovski [ mailto:george@oracle .caltech.edu ], S. R. Kulkarni, (Caltech [ http://astro.caltec…]) et al., Keck Observatory [ http://www2.keck.ha…]

gamma-rays

GRB

Hawaii

Goddard Space Flight Center (GSFC)

Washington, D.C.

Marshall Space Flight Center (MSFC)

Keck Observatory

http://antwrp.gsfc.…

SPD-APOD-ap980713