Targets of Opportunity

Swift is primarily a GRB mission intended to detect afterglows and conduct follow-up observations. However, Swift's rapid response capabilities make it an ideal observatory for a variety of astrophysical observations. Members of the astrophysics community may request Target of Opportunity observations with Swift. Requests for ToOs must be made using the Target of Opportunity Request Form.

Requests for ToO observations may involve any of Swift's instruments. The BAT and XRT select observing modes autonomously. The UVOT uses pre-defined observing sequences. Specific filters and modes may be requested subject to an instrumental safety check. Alternately, the selection of filters and modes may be left to the discretion of the Science Operations Team. Special filter requests should be made in the text box entitled ``Scientific Justification''. Unless otherwise specified and justified UVOT observations will usually be taken using the Filter of the Day.

After a ToO request has been submitted an automated response will be sent to the proposer within a few minutes. The ToO will be evaluated and the proposer will be notified of the decision within one business day. For time-critical observations notification may happen faster.

ToO requests are evaluated for visibility by Swift's instruments, utilization of Swift's unique capabilities, and potential impact on autonomous and pre-scheduled observations.

ToO requests are evaluated and approved/rejected by the mission's Principal Investigator. The following criteria will be applied to ToO requests.

• Does not impair Swift's capability for GRB detection and follow-up observations.
• Requires fast turn-around observations.
• Produces high impact science.
• Makes good use of Swift data. Swift data are a major component of the scientific results.
• Requires unique Swift capabilities.
• The Swift spacecraft can point anywhere in the sky except within 46 degrees of the Sun, 21 degrees of the Moon, and 6 degrees of the orbit pole, which precesses slowly. However, ToO requests at high hour angle to the Sun are more likely to be approved. Most desirable are those at $> 9$ hours from the Sun. The purpose of the anti-Sun restriction for ToOs is to keep the observatory pointing as much as possible toward the night sky to optimize follow-up observations of GRBs.
• ToO targets at more than 9 hours in RA from the Sun are more likely to be accepted and are observed at high priority when accepted unless they conflict with GRBs or other urgent targets. ToO targets at less than 9 hours may be accepted for scientifically compelling reasons, but are scheduled for limited exposure times of typically $< 4$ ks per day (with 2 ks per day being a standard value).

These criteria are a guide and may be relaxed or tightened in exceptional circumstances.

Requests may be made for follow-up observations of GRBs that have been detected by other satellites. Up-to-date information about the Swift ToO program can be found the Target of Opportunity Web Page.