Swift as a Rapid Wide Field Follow-up Instrument

John Nousek & Jamie KenneaPenn State University

Phil EvansUniversity of Leicester

International Workshop on Astronomical X-ray OpticsPrague, Czech Republic

8 December 2015

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¨ GRBs· >1000 GRBs with arcsec positions· Primary GRB mission into the future

¨ Non-GRBs· >1400 TOOs per year· AGN, SNe, novae, CVs, LMXBs, stars, comets, ...· First sensitive hard X-ray all sky survey

¨ GI program· > 4 oversubscription, $1.2M, 5Ms time per year

Swift – The World's GRB FactoryBAT

XRT

UVOT

Swift as an E-M counterpart finder

¨ Swift’s unique capabilities: · Performing rapid Target of Opportunity (TOO) observations

¾TDRSS and Groundstation uploads with low latency.· Rapid slewing allows for high efficiency/low overhead observing

¾Swift average slew rate ~0.6 deg/second. · Ability to see a large area of the sky over a short period (96 min

orbit) vs ground based observatories waiting for night-time, and latitude limited viewing areas.

How do we cover large regions?

¨ In-built tiling can cover hexagonal regions· 4, 7 point tiling utilized frequently by Swift· 19, 37 point tiling recently approved for use and tested (not yet

available to community)¾ 37-point tiling still only covers 1 degree radius error circle!

· Can cover larger regions by uploading multiple TOOs over multiple passes (e.g. IPN error regions).

¾ Inefficient and slow, plus large strain on SOT/FOT!

37-POINT TILING

1 orbit 37 point tiling test

Galaxy targeted search for GW

¨ EM GW search using galaxy targeting, i.e. implementing Phil Evans’ plan:

· First 48 hours, observe every targeted galaxy, selected by convolving GW error region with Galaxy Catalog initially, in descending order of probability, for 60s per field.

· Followed by covering as many galaxies as we can for 500s exposure each in following 4 days to search for afterglows of off-axis sGRBs.

¾ Expect to cover 300 Galaxies, observed in order of probability.

¨ Not previously possible with Swift, but two methods developed to do this:

· Upload lists of RA/Dec to cover non-circular error boxes. BAT FSW in development…

· “PPST Jamming” concept, requires alteration in ground operations, but not FSW.

¾PPST = Pre-Planned Science Timeline

Performing a PPST Jam

¨ Using Phil’s Galaxy Targeting software to generate a list of targets to observe.

¨ Merge this with existing PPST gaps in observations are filled with normal Swift targets

¨ Perform extensive validation of PPST product

¨ Upload to spacecraft for immediate execution at next ground station pass (adds latency - TDRSS can’t be used for this)

¨ Minimum exposure time is 60s per field (hard limit)

¨ Observations of a maximum of 450 targets in 24 hour period (set by onboard buffer size)

¨ So maximum amount of time spent doing this: ~25ks per day, about ~40-50% of available time (overheads are higher due to more slews).

SWIFT SLEW FREQUENCY

• Note previous maximum number of slews in one day is 174! With 450 Swift goes from being 6 observatories to 16 (thanks Rick Edelson!).

Pros and cons

¨ Pros

· Only way to cover large number of sources / sky area

· Can be done without FSW change - FSW change only allows us to get on target quicker.

· Testing appears to show that it’s not going to break Swift. More testing planned.

¨ Cons

· Will knock out a lot of targets when we’re concentrating on GW follow-up!

· BAT triggering severely impacted by short dwell time on tiles.

New Observing mode - new projects

¨ Ability to perform observations of many, short exposures opens up a new mode of operation for Swift!

¨ Large area surveys:

· Can survey whole of the SMC in ~24ks, down to a sensitivity of ~5% LEDD. SMC is packed full of HMXBs, Be/X-ray binaries and we tend to only see them go into outburst when INTEGRAL scans SMC.

· Regular Galactic Bulge survey? M31? LMC?

¨ GRB localization:

· Better coverage of IPN error boxes

· Localization of select GBM GRBs?

¨ Others?

STATUS

¨ 19 and 37 point tiling has been tested and approved for use.

· Importantly shows that many short (45-60s) exposures can be performed by Swift without harming spacecraft.

¨ Software to generate PPSTs from LIGO error regions has been written and tested.

¨ On-board testing to being very soon

· ALIGO is online, so we may get a trigger any day to follow!

· Expect mode to be fully commissioned before end of the year.

¨ Proposal submitted to Swift GI program to support this effort.