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drhex
2007-Oct-19, 11:40 AM
A recent entry by the Bad Astronomer,
http://www.badastronomy.com/bablog/2007/10/14/amateur/
speaks of an "amateur" astronomer looking at the afterglow of a GRB and how cool that is. He was apparently sent an email with the coordinates of the burst shortly after it was discovered by Swift or some other orbiting telescope.

So my question is, if the orbiting telescopes can detect the GBR and provide its coordinates and examining the afterglow quickly is important and interesting, why didn't the orbiting telescope study the afterglow itself immediately?

StupendousMan
2007-Oct-19, 12:54 PM
So my question is, if the orbiting telescopes can detect the GBR and provide its coordinates and examining the afterglow quickly is important and interesting, why didn't the orbiting telescope study the afterglow itself immediately?

A good place to go for information about gamma-ray bursts is the GRBlog:

http://grad40.as.utexas.edu/grblog.php

A few moments of searching brings up the announcement of this burst: it was detected by the SWIFT spacecraft -- which does have optical and UV cameras on board -- but as the announcement (GCN 6871 (http://grad40.as.utexas.edu/grblog.php?&get=GCN6871)) states:



At 20:45:47 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 071010B (trigger=293795). The BAT on-board calculated location is RA, Dec 150.530, +45.731 which is

RA(J2000) = 10h 02m 07s
Dec(J2000) = +45d 43' 53"

with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single FRED pulse with a duration of about 20 sec. The peak count rate was ~12,000 counts/sec (15-350 keV), at ~2 sec after the trigger.

Because Swift is in the process of returning to normal operations, automatic slewing to GRBs is currently disabled outside of business hours (US EDT). Therefore, there are no prompt XRT or UVOT observations of this burst.

So, the reason that SWIFT could not make its own followup observations is that it was unable to slew to the field. The gamma-ray burst instrument can detect radiation over very wide angles, but the optical and UV telescopes have small fields of view: the spacecraft must orient itself so that it points the telescopes in the proper direction.