Search for gravitational waves in coincidence with radio transients from pulsar surveys

1. Search for gravitational waves in coincidence with radio transients from pulsar surveys Brennan Hughey for the LIGO and Virgo Collaborations Amaldi 9 at Cardiff, Wales July 14th, 2011 LIGO DCC-G1100608

2. Joint Radio/Gravitational Wave Search • Looking for gravitational waves (GWs) in coincidence with • identified radio transients of unknown origin • Gravitational wave search externally triggered by EM • rather than initiating EM follow-up as in last few talks • Science goals are similar – increase GW detection • confidence and learn more about astrophysical system • than by a single messenger alone • Radio is specifically interesting for a number of reasons: • Scenarios where optical emission is much more • strongly beamed than radio or GW emission, • Dispersion measure plus direction provide a built-in • distance estimate • Several radio/GW collaborative efforts in progress, • We focus on GWs in coincidence with short duration • radio transients identified in pulsar surveys GW Radio

3. Joint Radio/Gravitational Wave Search • Looking for gravitational waves (GWs) in coincidence with • identified radio transients of unknown origin • Gravitational wave search externally triggered by EM • rather than initiating EM follow-up as in last few talks • Science goals are similar – increase GW detection • confidence and learn more about astrophysical system • than by a single messenger alone • Radio is specifically interesting for a number of reasons: • Scenarios where optical emission is much more • strongly beamed than radio or GW emission, • Dispersion measure plus direction provide a built-in • distance estimate • Several radio/GW collaborative efforts in progress, • We focus on GWs in coincidence with short duration • radio transients identified in pulsar surveys GW Radio

4. Radio Pulsar Surveys We are negotiating MoUs with 3 pulsar survey groups at 2 observatories • Robert C. Byrd Green Bank Telescope: • 100 X 110 meter fully steerable scope • at NRAO site in West Virginia • Green Bank Drift-scan survey: • Summer 2007, telescope fixed as Earth rotates • Green Bank survey of northern celestial cap: • 2009-2012. will cover sky north of 38 declination • Both GBT surveys have 350 MHz central frequency • Arecibo Observatory: • 305 meter diameter, located in Puerto Rico • Arecibo L-band Feed Array (ALFA) is a • 7-beam receiver operating at 20 cm • P-ALFA: March 2005 – present • 1.4 GHz central frequency, • 300 MHz bandwidth

5. Radio Propagation Time Delay Dispersion measure (electron density integrated over distance to source) used to calculate frequency dependent time delay of radio signal with respect to GW (or light in vacuum). Propagation delays at most extreme dispersion measure and lowest frequency for this analysis are not more than 46 seconds. Each of 7 ALFA beams SNR determines Best DM 124 different trial DM channels radio pulse From “An Arecibo Search for Pulsars and Transient Sources in M33” by N.D.R. Bhat et al., APJ 732 (2011) 14

6. Sources of Joint Emission Binary neutron star coalescence: Radio emission from magnetospheric interactions (e.g. astro-ph/0003218), Rapidly rotating post-merger object (arXiv:1004.5115), Plasma excitation via relativistic MHD followed by inverse compton scattering (gr-qc/0503074) Single neutron star (pulsar, RRAT): starquakes etc. Transient GW emission would in many cases be accompanied by a “glitch” in a steady state signal (e.g. James Clark’s talk) but beaming or other mechanisms could cause radio signal to manifest as a transient Cosmic strings: Cusps in cosmic strings could nearly simultaneously emit GWs and radio pulses (arXiv:0802.0711) NASA Ken Olum NASA

7. Other sources Some other scenarios for joint GW-radio emission are interesting but probably less relevant for this specific search. For example: GRB or SN afterglow: shortest radio afterglow scenario peaks ~20 minutes after coalescence in short GRB scenario (astro-ph/0701748v2), still too broad in duration for our radio pulses Prompt radio emission from GRBs: As discussed in astro-ph/0002278, simply too low frequency for our radio partners Primordial black hole dissipation, massive black hole tidal disruption or coalescence : Not promising as LIGO sources University of Warwick/Mark Galick Dana Berry, SkyWorks Digital

8. Analysis Design (I) Search for gravitational waves will be conducted with X-pipeline (arXiv:0908.3665), which was used to conduct many previous externally triggered GW analyses Resembles GRB searches (see Michal Was’s plenary talk tomorrow), with a factor of O(2) sensitivity improvement expected relative to an all-sky search Sample X-pipeline output from S5 GRB search: Background Sensitivity curve Efficiency for an injection Amplitude (Hz-1/2) fraction above loudest event frequency significance hrss amplitude Hz-1/2

9. Analysis Design (II) • Several parameters will be adjusted with respect to S6 GRB search: • Shorten time window • Change cut method to not require circular polarization • Expand frequency range • Add to set of injection types used • Analysis tuned on “Straw Man” data set of 5 hypothetical transients during S6/VSR2 • Will analyze real triggers once cuts are finalized and radio events are available…. • In summary: • Radio/GW observations are a promising avenue for multimessenger astronomy • We are developing an analysis to search for GWs in coincidence with radio • pulses of unknown origin in the few hundred MHz to GHz frequency range • Collaborative efforts between the radio and GW communities should pave the • way for further collaboration in the Advanced Detector era