Abstract
We report the first plausible optical electromagnetic counterpart to a (candidate) binary black hole merger. Detected by the Zwicky Transient Facility, the electromagnetic flare is consistent with expectations for a kicked binary black hole merger in the accretion disk of an active galactic nucleus [B. McKernan, K. E. S. Ford, I. Bartos, Astrophys. J. Lett. 884, L50 (2019)AJLEEY2041-821310.3847/2041-8213/ab4886] and is unlikely [<O(0.01%))] due to intrinsic variability of this source. The lack of color evolution implies that it is not a supernova and instead is strongly suggestive of a constant temperature shock. Other false-positive events, such as microlensing or a tidal disruption event, are ruled out or constrained to be <O(0.1%). If the flare is associated with S190521g, we find plausible values of total mass MBBH∼100 MM, kick velocity vk∼200 km s-1 at θ∼60° in a disk with aspect ratio H/a∼0.01 (i.e., disk height H at radius a) and gas density ρ∼10-10 g cm-3. The merger could have occurred at a disk migration trap (a∼700rg; rgGMSMBH/c2, where MSMBH is the mass of the active galactic nucleus supermassive black hole). The combination of parameters implies a significant spin for at least one of the black holes in S190521g. The timing of our spectroscopy prevents useful constraints on broad-line asymmetry due to an off-center flare. We predict a repeat flare in this source due to a reencountering with the disk in ∼1.6 yr(MSMBH/108 MM)(a/103rg)3/2.
| Original language | English |
|---|---|
| Article number | 251102 |
| Journal | Physical Review Letters |
| Volume | 124 |
| Issue number | 25 |
| DOIs | |
| State | Published - 26 Jun 2020 |
| Externally published | Yes |
Bibliographical note
Publisher Copyright:© 2020 American Physical Society.
Funding
We thank the referees for useful, timely comments that have improved this manuscript. M. J. G. is supported by NSF Grants No. AST-1518308 and AST-1815034, and NASA Grant No. 16-ADAP16-0232. K. E. S. F. and B. M. are supported by NSF Grant No. AST-1831415 and Simons Foundation Grant No. 533845. K. E. S. F. and B. M. acknowledge extremely useful conversations with Mordecai-Mark MacLow and Pierre Marchand. The work of D. S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. M. M. K. acknowledges the GROWTH project funded by the National Science Foundation under Grant No. 1545949. M. C. is supported by NSF Grant No. PHY-2010970. Based on observations obtained with the Samuel Oschin 48-inch telescope and the 60-inch telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Z. T. F. is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by Caltech Optical Observatories, IPAC, and University of Washington. The ZTF forced-photometry service was funded under the Heising–Simons Foundation Grant No. 12540303 (PI: Graham). N. P. R. acknowledges support from the STFC and the Ernest Rutherford Fellowship scheme.
| Funders | Funder number |
|---|---|
| Deutsches Elektronen-Synchrotron and Humboldt University | |
| Heising-Simons Foundation | 12540303 |
| IPAC | |
| Weizmann Institute for Science | |
| National Science Foundation | PHY-2010970, AST-1518308, AST-1440341, AST-1815034, 1545949 |
| National Aeronautics and Space Administration | 16-ADAP16-0232, AST-1831415 |
| Simons Foundation | 533845 |
| Lawrence Berkeley National Laboratory | |
| University of Wisconsin-Milwaukee | |
| California Institute of Technology | |
| University of Washington | |
| University of Maryland | |
| Los Alamos National Laboratory | |
| Science and Technology Facilities Council |