Related papers: A Supermassive Binary Black Hole Candidate in Mrk …
With evidence for a nanohertz gravitational-wave background now established by Pulsar Timing Arrays, the search focuses on identifying individual supermassive black hole binaries. We show that these binaries produce a distinct spatial…
Pulsar timing is a promising technique for detecting low frequency sources of gravitational waves. Historically the focus has been on the detection of diffuse stochastic backgrounds, such as those formed from the superposition of weak…
The Legacy Survey of Space and Time (LSST) by the Vera C. Rubin Observatory is expected to discover tens of millions of quasars. A significant fraction of these could be powered by coalescing massive black hole (MBH) binaries, since many…
The TeV BL Lac object Markarian 501 has been the subject of a 4.5 month multi-instrument campaign conducted in 2009, which provided an excellent temporal and energy coverage from radio to very high energy gamma rays (>100 GeV, VHE). During…
We investigate the time-varying electromagnetic emission of a low-mass-ratio supermassive black hole binary (SMBHB) embedded in a circumprimary disk, with a particular interest in variability of shocks driven by the binary. We perform a 2D,…
We have monitored the R and I magnitudes of the black hole candidate system A0620-00 (V616 Mon) in the years 1991-95 at the Wise Observatory. Combining our data with some additional measurements, we analyze a sparsely covered 7 years light…
A MHz gravitational wave search for harmonic sources was conducted using a 704-hr dataset obtained from the Holometer, a pair of 40-meter power recycled Michelson interferometers. Our search was designed to look for cosmic string loops and…
Recent analysis of the long term radio lightcurve of the extremely variable BL Lacertae object AO 0235+16 by Raiteri et al. (2001) have revealed the presence of recurrent outbursts in this source with a period of ~ 5.7 +/- 0.5 yr.…
Studying a centi-parsec supermassive black hole binary (SMBHB) would allow us to explore a new parameter space in active galactic nuclei, and these objects are also potential sources of gravitational waves. We report evidence that an SMBHB…
The use of a high precision pulsar timing array is a promising approach to detecting gravitational waves in the very low frequency regime ($10^{-6} -10^{-9}$ Hz) that is complementary to the ground-based efforts (e.g., LIGO, Virgo) at high…
Abridged: Supermassive black hole binaries (SMBHBs) separated by (sub)-pc scales represent one of the latest stages of hierarchical galaxy assembly. However, many of these objects are hidden behind large columns of gas and dust at the…
As gravitational wave astronomy has entered an era of routine detections, it becomes increasingly important to precisely measure the physical parameters of individual events and infer population properties. Eccentricity is a key observable,…
Gravitational waves from the inspiral and coalescence of supermassive black-hole (SMBH) binaries with masses ~10^6 Msun are likely to be among the strongest sources for the Laser Interferometer Space Antenna (LISA). We describe a…
We present the results of our power spectral analysis for the BL Lac object PKS 0735+178 utilizing the Fermi-LAT survey at high-energy $\gamma$-rays, several ground-based optical telescopes, and single-dish radio telescopes operating at GHz…
Multiwavelength monitoring observations of Sagittarius A* exhibit variability on timescales of minutes to hours, indicating emission regions localized near the event horizon. (Sub)Millimeter-wavelength VLBI is uniquely suited to probe the…
We explicitly demonstrate that current numerical relativity techniques are able to accurately evolve black hole binaries with mass ratios of the order of 1000:1. This proof of principle is relevant for future third generation (3G)…
We have observed and analysed the eclipses of the black widow pulsar J1810+1744 at low radio frequencies. Using LOw-Frequency ARray (LOFAR) and Westerbork Synthesis Radio Telescope observations between 2011--2015 we have measured variations…
It is known that massive black holes (MBHs) of $10^{5-7}\,M_\odot$ could capture small compact objects to form extreme-mass-ratio inspirals (EMRIs). Such systems emit gravitational waves (GWs) in the band of the Laser Interferometer Space…
GW190521 is the most massive merging binary black hole (BBH) system detected so far. At least one of the component BHs was measured to lie within the pair-instability supernova (PISN) mass gap ($\sim 50-135\;{\rm M}_{\odot}$), making its…
Blazar OJ287 is a unique source in which optical outbursts with double-peak structure have been observed quasi-periodically with a cycle of 12yr. It may be one of the best candidates for searching supermassive black hole binaries. We…