Guidelines for the GRB Target-of-Opportunity Program for Carnegie/CfA Observers
The Time Assignment
Committees for the Carnegie Observatories and the Harvard-Smithsonian
for Astrophysics (CfA) have allocated interrupt time on the Magellan
Telescopes in the 2008B semester to support Edo Berger's study of the
properties of Gamma Ray Bursts (GRB). Given the importance of the
program and the need to collect as complete a sample of objects as
possible with minimum interruption to observers, this note describes
the guidelines for these observations to clarify the roles of Carnegie
and CfA observers and to encourage their continued collaboration with
Edo in this work. We have an opportunity with the excellent instruments
on the Magellan telescopes to support Edo's research and to have a major
impact on the study of GRB's.
The science goals of the CfA/Carnegie gamma-ray burst follow-up program
focus on the rapid identification and spectroscopy of GRB afterglows,
with particular attention given to short-duration and high redshift
GRBs. Because of the unpredictable nature of GRBs and their timing, as
well as changing conditions at the telescope, unusual situations beyond
the scope of these basic guidelines may arise. As a result, an open
exchange of information between the observer and Edo is encouraged and
Carnegie and CfA observers are strongly encouraged to participate in the
GRB follow-up program outlined in this document.
GRB observations should be executed as soon as possible following a request,
subject to conditions at the telescope. This is designed to increase the
scientific returns of the observation and, given the usual rapid decline
in the brightnesses of the GRB afterglows, to save time for the observer.
The decision to immediately terminate any long exposure is left to the
observer. It is Edo's responsibility to supply information on the urgency
of the request and any relevant scientific details. Setup and observing
time will be counted in the total of allocated observing hours.
The observer should send a brief account of the total time used (on source
and overhead) from the time the observations were initiated to the time the
normal program was resumed to Ian Thompson and to Scott Kenyon for each
interrupt observation, and to include this information in the usual nightly
Carnegie and CfA observers are encouraged to observe GRB targets for Edo
before responding to requests from individuals outside of the Carnegie/CfA
GRB program. It is recognized that many observers have ongoing collaborations
with non-Carnegie and non-CfA observers who have an interest in GRB's. The
success of Edo's program relies on the cooperation of his colleagues, and
observers should take this into consideration before responding to other
requests for GRB data.
An override observation shall not exceed 1.5 hours, unless agreed to by the
observer. A typical request is expected to be about 1 hour (on-source) for
spectroscopy, and about 0.5-1 hour for imaging (e.g., search for a short GRB).
Multiple overrides during an individual observing run are possible, for timely
followup observations can sometimes significantly increase the value of a set
of data on a GRB.
A change of instrument for the purpose of a GRB observation is indicated
in the most extreme circumstances (e.g., a very bright high redshift GRB).
It is Edo's responsibility to explain the scientific reasons for such a
change. The extra time required to switch back and forth will be charged
to the GRB program. Such a change can only occur if the second instruments
is ready for observations and the scheduled observer is skilled in its use.
Wendy Freedman & Charles Alcock
Directors, Carnegie Observatories & Harvard-Smithsonian Center for