European Pulsar Timing Array limits on continuous gravitational waves from individual supermassive black hole binaries

Abstract

We have searched for continuous gravitational wave (CGW) signals produced by individually resolvable, circular supermassive black hole binaries (SMBHBs) in the latest EPTA dataset, which consists of ultra-precise timing data on 41 millisecond pulsars. We develop frequentist and Bayesian detection algorithms to search both for monochromatic and frequencyevolving systems. None of the adopted algorithms show evidence for the presence of such a CGW signal, indicating that the data are best described by pulsar and radiometer noise only. Depending on the adopted detection algorithm, the 95% upper limit on the sky-averaged strain amplitude lies in the range 6 × 10 −15 < A < 1.5 × 10 −14 at 5nHz < f < 7nHz. This limit varies by a factor of five, depending on the assumed source position, and the most constraining limit is achieved towards the positions of the most sensitive pulsars in the timing array. The most robust upper limit -obtained via a full Bayesian analysis searching simultaneously over the signal and pulsar noise on the subset of ours six best pulsars -is A ≈ 10 −14 . These limits, the most stringent to date at f < 10nHz, exclude the presence of sub-centiparsec binaries with chirp mass M c > 10 9 M out to a distance of about 25Mpc, and with M c > 10 10 M out to a distance of about 1Gpc (z ≈ 0.2). We show that state-of-the-art SMBHB population models predict < 1% probability of detecting a CGW with the current EPTA dataset, consistent with the reported non-detection. We stress, however, that PTA limits on individual CGW have improved by almost an order of magnitude in the last five years. The continuing advances in pulsar timing data acquisition and analysis techniques will allow for strong astrophysical constraints on the population of nearby SMBHBs in the coming years.

The puzzling case of the radio-loud QSO 3C 186: a gravitational wave recoiling black hole in a young radio source?

“…GWs from ∼30 M merging BHs were recently detected by LIGO (Abbott et al 2016) and pulsar timing experiments (EPTA, PPTA, and SKA in the future) will in the future be able to detect GWs of the frequency expected from mergers of BHs with masses similar to that of 3C 186 (Moore et al 2015;Babak et al 2016;Madison et al 2016). …”

Limits on Anisotropy in the Nanohertz Stochastic Gravitational Wave Background

“…Sesana and Vecchio [43] find that the angular resolution of a PTA for a resolvable GW source is ΔΩ ∝ 50ð50=N psr Þ 1=2 ð10=SNRÞ 2 deg 2 , and this resolution sets an upper bound on l via l ¼ 180=θ, where θ ¼ ffiffiffiffiffiffiffi ffi ΔΩ p [29]. We analyze a subset of the six best pulsars in the EPTA [19] that encapsulate ∼95% of the full-array SNR in simulated continuous GW searches [44]: PSRs J0613 − 0200, J1012 þ 5307, J1600 − 3053, J1713 þ 0747, J1744 − 1134, J1909 − 3744, where T max ¼ 17.7 years and the GW frequencies with which we characterize red-noise components are ∈ ½1=T max ¼ 1.79; 50=T max ¼ 89.7 nHz . Hence, in our array subset l max ≲ 4.…”

Hypermassive Black Hole Shines in the Childhood Universe

“…To form more massive BHs by merging smaller BHs, the key issue is the merging frequency in the Universe. The results of several Pulsar Timing Array (PTA) experiments so far do not support this frequent merging hypothesis [14,15,16,17].…”

“…There is evidence for likely BH mergers but they are not that frequent as constrained by several up-todate PTA results [14,15,16,17]. The initial spatial distribution of angular momentum within host halos and/or reservoirs can have various conceivable forms.…”