TITLE: GCN CIRCULAR NUMBER: 26243 SUBJECT: LIGO/Virgo S191110af: Potential pulsar counterparts DATE: 19/11/13 19:39:30 GMT FROM: David Kaplan at UW-Milwaukee David Kaplan and John Friedman (University of Wisconsin-Milwaukee), and Jocelyn Read (CSU Fullerton, Caltech) report on behalf of the GROWTH collaboration: The unmodelled GW burst S191110af (LVC, GCN 26222) consisted of a narrow-band signal near 1781.72 Hz with duration 0.1 s. This frequency is consistent with the frequency of the fundamental quadrupole mode of a star with mass in the range of 1.2 to 1.45 Msun and radii within current estimates. We use Andersson & Kokkotas (1998, MNRAS, 299, 10591068) Eqs. (1), (5) and (8) for the frequency, damping time, and effective amplitude of the quadrupole f mode. In particular, for a neutron star with mass 1.25 Msun, a frequency of 1782 Hz corresponds to radius 13.3 km, and the damping time is then 0.2 s, consistent with observations. Similarly, the range of EOS considered in Chirenti et al. (2015, Phys. Rev. D 91, 044034) generate f-modes along a band in frequency and decay time that seems compatible with this candidate. While we do not know the strain amplitude associated with this burst, we can estimate a minimum detectable strain based on the observed frequency, duration, and the LIGO noise properties. At the observed frequency we estimate a noise level of 1.5e-23 Hz**-0.5 (https://www.gw-openscience.org/detector_status/day/20191110/). Following Eqs. (3) and (4) of Kokkotas et al. (2001, MNRAS, 320, 307) we estimate that a signal with f=1782Hz and duration 0.15s will have amplitude 5e-22, and SNR~10 in a detector with noise 1.5e-23 Hz**-0.5, for a source at 1kpc emitting 2.5e-9 Msun c**2 of energy in gravitational waves. Comparably, in a physical model where similar oscillations come from a pulsar triggered by a significant glitch, Keer & Jones (2015, MNRAS, 446, 865) estimate a stain of 3e-22 at a distance of 1 kpc. Motivated by this, we searched for potential counterparts among known pulsars (note that if such a signal originates with a neutron star it need not be visible as a pulsar). Based on the amplitude estimates referenced above, we restrict our search to Galactic pulsars and do not consider significantly more distant objects. We looked at the latest version (1.61) of the ATNF pulsar catalog (Manchester et al. 2005, AJ, 129, 1993; http://www.atnf.csiro.au/research/pulsar/psrcat) and computed the probability of the GW sky map at the position of each pulsar. The top 3 pulsars ranked by probability are: PSR J0045-7042 1.6e-3 PSR J0101-6422 2.4e-4 PSR B2045-16 4.9e-5 All other pulsars have probabilities <3e-5, and do not stand out from the rest of the population, with 394 other sources at probabilities >1e-6. For these three pulsars: PSR J0045-7042 is a slow (0.6s period) pulsar in the Small Magellanic Cloud, and would not appear to be sufficiently energetic or close enough to give rise to a significant GW signal. PSR J0101-6422 is a nearby (~1 kpc), energetic (rotational energy loss 1.2e34 erg/s) millisecond pulsar in a 1.8d orbit, which is also a Fermi gamma-ray source (Kerr et al. 2012, ApJ, 748, 2; Nolan et al. 2012, ApJS, 199, 31). PSR J2045-16 is a nearby (~0.8 kpc) slow (2.0s period) pulsar, which does not appear otherwise notable. Unfortunately, PSRs J0045-7042 and B2045-16 do not have sufficient timing data to search for a recent glitch. PSR J0101-6422 is timed regularly with the Fermi Large Area Telescope, but detecting a putative glitch will take weeks to months, depending on the magnitude of the glitch (M. Kerr and P.S. Ray, private communication). As mentioned above, any or none of these sources could be the origin of the possible gravitational wave emission, or the candidate could be terrestrial in origin. It also may be worth searching for short GW bursts associated with known glitches, especially those from the Vela pulsar (as in Abadie et al. 2011, PRD 83, 042001). We thank Joe Swiggum, Sinead Walsh, Nils Andersson, and Cecilia Chirenti for helpful conversations. GROWTH is a worldwide collaboration comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU USA and USyd, Australia. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.