The accretion disks of active galactic nuclei (AGNs) are promising locations for the merger of compact objects detected by gravitational wave (GW) observatories. Embedded within a baryon-rich, high-density environment, mergers within AGNs are the only GW channel where an electromagnetic (EM) counterpart must occur (whether detectable or not). Considering AGNs with unusual flaring activity observed by the Zwicky Transient Facility (ZTF), we describe a search for candidate EM counterparts to binary black hole (BBH) mergers detected by LIGO/Virgo in O3. After removing probable false positives, we find nine candidate counterparts to BBH mergers during O3 (seven in O3a, two in O3b) with a
- NSF-PAR ID:
- 10493996
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 963
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 98
- Size(s):
- ["Article No. 98"]
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract p -value of 0.0019. Based on ZTF sky coverage, AGN geometry, and merger geometry, we expect ≈3(N BBH/83)(f AGN/0.5) potentially detectable EM counterparts from O3, whereN BBHis the total number of observed BBH mergers andf AGNis the fraction originating in AGNs. Further modeling of breakout and flaring phenomena in AGN disks is required to reduce our false-positive rate. Two of the events are also associated with mergers with total masses >100M ⊙, which is the expected rate for O3 if hierarchical (large-mass) mergers occur in the AGN channel. Candidate EM counterparts in future GW observing runs can be better constrained by coverage of the Southern sky as well as spectral monitoring of unusual AGN flaring events in LIGO/Virgo alert volumes. A future set of reliable AGN EM counterparts to BBH mergers will yield an independent means of measuring cosmic expansion (H 0) as a function of redshift. -
more » « less
ABSTRACT The detection of an intermediate-mass black hole population (102–106 M⊙) will provide clues to their formation environments (e.g. discs of active galactic nuclei, globular clusters) and illuminate a potential pathway to produce supermassive black holes. Ground-based gravitational-wave detectors are sensitive to mergers that can form intermediate-mass black holes weighing up to ∼450 M⊙. However, ground-based detector data contain numerous incoherent short duration noise transients that can mimic the gravitational-wave signals from merging intermediate-mass black holes, limiting the sensitivity of searches. Here, we follow-up on binary black hole merger candidates using a ranking statistic that measures the coherence or incoherence of triggers in multiple-detector data. We use this statistic to rank candidate events, initially identified by all-sky search pipelines, with lab-frame total masses ≳ 55 M⊙ using data from LIGO’s second observing run. Our analysis does not yield evidence for new intermediate-mass black holes. However, we find support for eight stellar-mass binary black holes not reported in the first LIGO–Virgo gravitational wave transient catalogue GWTC-1, seven of which have been previously reported by other catalogues.
-
more » « less
Abstract Electromagnetic follow-up of gravitational-wave detections is very resource intensive, taking up hours of limited observation time on dozens of telescopes. Creating more efficient schedules for follow-up will lead to a commensurate increase in counterpart location efficiency without using more telescope time. Widely used in operations research and telescope scheduling, mixed-integer linear programming is a strong candidate to produce these higher-efficiency schedules, as it can make use of powerful commercial solvers that find globally optimal solutions to provided problems. We detail a new target-of-opportunity scheduling algorithm designed with Zwicky Transient Facility in mind that uses mixed-integer linear programming. We compare its performance to
gwemopt , the tuned heuristic scheduler used by the Zwicky Transient Facility and other facilities during the third LIGO–Virgo gravitational-wave observing run. This new algorithm uses variable-length observing blocks to enforce cadence requirements and to ensure field observability, along with having a secondary optimization step to minimize slew time. We show that by employing a hybrid method utilizing both this scheduler andgwemopt , the previous scheduler used, in concert, we can achieve an average improvement in detection efficiency of 3%–11% overgwemopt alone for a simulated binary neutron star merger data set consistent with LIGO–Virgo’s third observing run, highlighting the potential of mixed-integer target of opportunity schedulers for future multimessenger follow-up surveys. -
Abstract The detection of a neutron star merger by the Advanced Laser Interferometer Gravitational-Wave Observatory and Advanced Virgo gravitational wave detectors, and the subsequent detection of an electromagnetic counterpart have opened a new era of transient astronomy. With upgrades to the Advanced Laser Interferometer Gravitational-Wave Observatory and Advanced Virgo detectors and new detectors coming online in Japan and India, neutron star mergers will be detected at a higher rate in the future, starting with the O3 observing run which will begin in early 2019. The detection of electromagnetic emission from these mergers provides vital information about merger parameters and allows independent measurement of the Hubble constant. The Australian Square Kilometre Array Pathfinder is expected to become fully operational in early 2019, and its 30 deg 2 field of view will enable us to rapidly survey large areas of sky. In this work we explore prospects for detecting both prompt and long-term radio emission from neutron star mergers with Australian Square Kilometre Array Pathfinder and determine an observing strategy that optimises the use of telescope time. We investigate different strategies to tile the sky with telescope pointings in order to detect radio counterparts with limited observing time, using 475 simulated gravitational wave events. Our results show a significant improvement in observing efficiency when compared with a naïve strategy of covering the entire localisation above some confidence threshold, even when achieving the same total probability covered.more » « less
-
more » « less
Abstract In 2017, the LIGO and Virgo gravitational-wave (GW) detectors, in conjunction with electromagnetic (EM) astronomers, observed the first GW multimessenger astrophysical event, the binary neutron star (BNS) merger GW170817. This marked the beginning of a new era in multimessenger astrophysics. To discover further GW multimessenger events, we explore the synergies between the Transiting Exoplanet Survey Satellite (TESS) and GW observations triggered by the LIGO–Virgo–KAGRA Collaboration (LVK) detector network. TESS's extremely wide field of view (∼2300 deg2) means that it could overlap with large swaths of GW localizations, which often span hundreds of square degrees or more. In this work, we use a recently developed transient detection pipeline to search TESS data collected during the LVK’s third observing run, O3, for any EM counterparts. We find no obvious counterparts brighter than about 17th magnitude in the TESS bandpass. Additionally, we present end-to-end simulations of BNS mergers, including their detection in GWs and simulations of light curves, to identify TESS's kilonova discovery potential for the LVK's next observing run (O4). In the most optimistic case, TESS will observe up to one GW-found BNS merger counterpart per year. However, TESS may also find up to five kilonovae that did not trigger the LVK network, emphasizing that EM-triggered GW searches may play a key role in future kilonova detections. We also discuss how TESS can help place limits on EM emission from binary black hole mergers and rapidly exclude large sky areas for poorly localized GW events.
