Supernova Observations

Swift is engaged in a long-term project to study SNe. Observers are encouraged to submit SN targets using the ToO process. In order for SNe to be considered for observation by Swift the following criteria must be met. These criteria are guidelines and may be relaxed or tightened in exceptional circumstances. The final decision to observe a SN will be made by the mission's Principal Investigator.

Nearby

Nearby SNe (i.e., those with $z < 0.01$, or within approximately 50 Mpc, or $v \le 3000$ km/s) are better detected by UVOT and more likely to be detected by the XRT. Since SNe Ia are brighter, and young SNe II are blue, we can observe SNe at greater distances, but 50 Mpc is usually the most distant that good detections are possible in all six UVOT filters in a 2000 s exposure for SNe within a week of maximum light.

Young (pre-maximum)

For both X-ray detection, and good sampling of the UV/optical peak, the SNe needs to be young. This can be determined through evidence for a rising light curve, a recent non-detection, or some sort of photometric or spectroscopic typing. The UV peaks a few days before the optical, so SNe should be several days before maximum light in the optical to be considered.

Good Location

To maximize the science return from the observations the SN should be well-suited for observations by the UVOT. This depends on the location of the SN within its host galaxy, but typically means that the SN should be at least 8 arcsec from the nucleus or any other bright source.

Low Extinction

Extinction in the Milky Way or in the host affects the UV more strongly than the optical, so a small amount of extinction can make it impossible to observe a SN in the UV. SNe should have extinctions of less than $A_V = 1$ mag, which corresponds to 2.3 mag in uvw1 and 2.8 mag in uvw2. The uvm2 filter is located on the interstellar extinction bump, which can make detection of a SN in that filter difficult.

Low GRB Impact

Swift is primarily a GRB mission, so observations of SNe must not interfere with GRB observations. To limit the impact of SNe observations on GRB studies an SN should be at least 60 degrees of RA from any GRB that is in Swift's observing schedule. In addition SNe should be at least 90 degrees from the Sun.