Electromagnetic Follow-ups of LIGO/Virgo Triggers

1. Electromagnetic Follow-upsof LIGO/Virgo Triggers Brennan Hughey* MIT Postdoc Symposium March 12th 2010 * reporting on the work of many people, including Erik Katsavounidis, Jeroen Hoeman and Joel Fridriksson at MIT

2. Gravitational Wave Physics(extremely abridged version) • Gravitational waves are distortions in space itself which are predicted by General Relativity • Their amplitude is measured in strain: h = L/L • They have 2 polarizations at 45 angles • They have not been directly observed • but indirect evidence exists: PSR1913+16 • Gravitational wave interferometers • use interference patterns of lasers • shot down perpendiculars arms • to attempt to measure miniscule • strain from passing gravitational • waves

3. GEO600 The Worldwide Network of Gravitational Wave Interferometers LIGO Hanford TAMA, CLIO 600 m 4 km2 km 300 m100 m 3 km 4 km LIGO Livingston VIRGO

4. Selected Results from LIGO’s 5thScience Run and Virgo’s First Science Run No detections, upper limits only Crab pulsar: limit GW radiation to 2% or less of available spin down power (factor of 7 in GW strain below spin down limit) GRB070201: GW emission constrained to not be binary merger in M31 Stochastic: energy density of stochastic GW background 0 < 6.9 × 10–6 around 100 Hz: places constraints on cosmic superstring models, models of early universe evolution and beats Indirect Big Bang nucleosynthesis limits All groups continue to improve upper limits for a variety of systems and scenarios Full S5/VSR1 upper limits for burst all sky analysis shown on right

5. Where we are now Work is well underway on 2nd generation instruments Advanced LIGO/Advanced Virgo coming in 2014 or 2015: sensitivity improved by order of magnitude in strain Currently we are in the S6/VSR2 science run July 2009 to ~July 2010 with some commissioning breaks LIGO sensitivity is comparable to S5, Virgo sensitivity improved Prototyping some components for Advanced LIGO and trying some new approaches to analysis……

6. Online Rapid Analysis Major effort amongst burst group and others in LIGO to produce rapid results in S6. • Interferometers produce • strain data with • preliminary calibration • Data transferred to • central site and • coherent burst • analysis is performed • Online data quality • standards cuts • generated and applied • Background estimated • with timeslides on cluster • First pass at data in ~10 minutes rather than months to years

7. Motivation • Assist detector characterization efforts • Expedite offline analysis • Work towards making LIGO/Virgo an integral part of the astronomical community • Quicker follow-up of events from other observatories • Produce event candidates for follow-up at other astronomical observatories NASA

8. Electromagnetic follow-ups Gravitational wave and electromagnetic emission from same source is not guaranteed, but many candidates exist (GRBs, SN, SGR….) and science payout could be huge: • Gravitational Wave Signal • Bulk motion dynamics • Luminosity distance • Progenitor mass • Light curve and spectrum • Host galaxy • Gas environment • Red shift distance • Confirm GW detection Multi-messenger astrophysics!! Measure Hubble constant Full picture of progenitor physics

9. Partner Instruments TAROT Chile & France Swift Satellite QUEST camera onESO Schmidt Telescope • UV/optical telescope: 0.4x0.4 sq. deg. FOV • X-ray telescope: 0.3x0.3 sq. deg. FOV • 4.1 x 4.6 deg FOV • Survey telescope for supernovas, etc. • 1.85 x 1.85 deg. FOV • History of GRB follow-ups

10. Events for Follow-up • Automated event processing takes 5-10 minutes: • Events which meet False Alarm Rate criteria • (one per day* for QUEST / Tarot, one per month* for Swift) • and pass automated cuts trigger e-mails and text messages • Human component takes additional 20-35 minutes: • Designated human on-shift leaps into action, performing • sanity checks and talking to all 3 control rooms to vet event • Events which pass are then submitted for follow-up, and • observed as target of opportunity when able * Note that we’re not talking about gravitational wave detections here, just more interesting than average triggers

11. Position reconstruction • Formal study over a broad range of simulated signals added on S5/VSR1 and S6/VSR2 instrument data • Performance varies significantly with signal-to-noise ratio (SNR), morphology, analysis parameters • Several degree error regions (“ears” not “eyes”) Position error areas hide the fact that they may be broken down to many disjoint patches

12. Position Reconstruction Known mass sourcein local universe X Regions consistent with GW datamay be many disjoint regions Chosen telescope pointing based on mass distribution and GW data

13. December – January Run • After test period, program went live from • Dec 20th 2009 through Jan 8th 2010 • (ended by Virgo commissioning) • 8 events sent for follow-ups, 3 followed up by QUEST • and 1 by TAROT • 1 “Engineering run” Swift observation • Series of collected images currently being studied: • hands on study will help us understand challenges of • linking GW and EM observations

14. Future Prospects • 2nd observation period (hopefully) coming this summer • - criteria for follow-ups and mass targeting being refined • - will attempt to increase automation • Compact Binary Coalescence group working towards • inclusion in EM follow-ups program as well • Discussions ongoing with other experiments • - Pi of the Sky: improved sky coverage • - Radio telescopes • Successful program paves the way for Advanced detector era