Search for ultralight bosons in Cygnus X-1 with Advanced LIGO
Ultralight scalars, if they exist as theorized, could form clouds around rapidly rotating black holes. Such clouds are expected to emit continuous, quasimonochromatic gravitational waves that could be detected by LIGO and Virgo. Here we present results of a directed search for such signals from the Cygnus X-1 binary, using data from Advanced LIGO's second observing run. We find no evidence of gravitational waves in the 250–750 Hz band. Without incorporating existing measurements of the Cygnus X-1 black hole spin, our results disfavor boson masses in the range 5.8 ≤ μ/(10⁻¹³ eV) ≤ 8.6, assuming that the black hole was born 5×10⁶ years ago with a nearly extremal spin. We then focus on a string axiverse scenario, in which self-interactions enable a cloud for high black-hole spins consistent with measurements for Cygnus X-1. In that model, we constrain the boson masses in the range 9.6≤μ/(10⁻¹³ eV) ≤ 15.5 for a decay constant f_a∼10¹⁵ GeV. Future applications of our methods to other sources will yield improved constraints.
© 2020 American Physical Society. Received 25 September 2019; accepted 2 March 2020; published 17 March 2020. We are grateful to Marianne Heida and Riley M. Connors for discussions and suggestions about the source parameters, and the LIGO and Virgo Continuous Wave Working Group for discussions and comments. This search uses LIGO data from the Gravitational Wave Open Science Center (https://www.gw-openscience.org). The authors are grateful for computational resources provided by the LIGO Laboratory. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation, and operates under cooperative agreement PHY–0757058. Advanced LIGO was built under award PHY–0823459. Support for this work was provided by NASA through the NASA Hubble Fellowship Grant No. HST–HF2–51410.001–A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under Contract No. NAS5–26555. R. B. acknowledges financial support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant agreement No. 792862. This work was written in part at the Aspen Center for Physics, which is supported by National Science Foundation Grant No. PHY–1607611. This paper carries LIGO Document No. LIGO–P1900274. M. I. is a NHFP Einstein fellow.
Published - PhysRevD.101.063020.pdf
Submitted - 1909.11267.pdf
Erratum - PhysRevD.102.089902.pdf