Related papers: A Supermassive Binary Black Hole Candidate in Mrk …

Beyond LISA, proposed space-based gravitational wave (GW) missions aim to explore the sub-millihertz to microhertz frequency band, with one key objective being the detection of massive binary black hole (MBBH) mergers across cosmic…

We model the electromagnetic emission signatures of massive black hole binaries (MBHBs) with an associated gas component. The method comprises numerical simulations of relativistic binaries and gas coupled with calculations of the physical…

We present new spectroscopic observations that are part of our continuing monitoring campaign of 88 quasars at z<0.7 whose broad H$\beta$ lines are offset from their systemic redshifts by a few thousand km/s. These quasars have been…

Variable active galactic nuclei showing periodic light curves have been proposed as massive black hole binary (MBHB) candidates. In such scenarios the periodicity can be due to relativistic Doppler-boosting of the emitted light. This…

We present a complete pipeline for detecting and characterizing gravitational waves (GWs) produced by the inspiral of stellar-mass binary black holes in data from the Laser Interferometer Space Antenna (LISA). The analysis framework relies…

We have assembled the historical light curves of the BL Lac Object 3FGL J0449.4-4350 at optical and gamma-ray bands, the time spanning about 10 years, analyzed the periodic variability of the light curves by using four different methods…

In order to search for the evidence of quasi-periodic oscillation (QPO) in blazar, multicolor optical observations of the BL Lacertae object S5 0716+714 were performed from 2005 to 2012. For $I$ band on March 19 2010 with low variability…

We have monitored the BL Lac object Mrk 501 in optical $V$, $R$ and $I$ bands from 2010 to 2015. For Mrk 501, the presence of strong host galaxy component can affect the results of photometry. After subtracting the host galaxy…

Blazars present highly variable $\gamma$-ray emission. This variability, which can range from a few minutes to several years, is also observed at other wavelengths across the entire electromagnetic spectrum. We make use of the first 12…

We have searched quasi-periodic oscillations (QPOs) for BL Lac PKS J2134-0153 in the 15 GHz radio light curve announced by the Owens Valley Radio Observatory 40-m telescope during the period from 2008-01-05 to 2019-05-18, utilizing the…

Hierarchical assembly models predict a population of supermassive black hole (SMBH) binaries. These are not resolvable by direct imaging but may be detectable via periodic variability (or nanohertz frequency gravitational waves). Following…

Massive black hole binary systems, with masses in the range ~10^4-10^10 \msun, are among the primary sources of gravitational waves in the frequency window ~10^-9 Hz - 0.1 Hz. Pulsar Timing Arrays (PTAs) and the Laser Interferometer Space…

In this work, we have searched quasi-periodic oscillations (QPOs) in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory (OVRO) 40 m telescope during the period from January 9,2008 to May…

On $2024$ October $5$, BL Lacertae ($2200+420$) experienced one of its brightest gamma-ray flares. We conducted simultaneous follow-up observations in the $u$, $v$, $g$, $r$, $i$, and $z$ bands from $2024$ October $17$ to November $21$…

We report a candidate centi-parsec supermassive black hole binary (SMBHB) in the radio-quiet quasar SDSS J0159+0105 at z=0.217. With a modified lomb-scargle code GLSdeDRW and the auto-correlation analysis ACF, we detect two significant (at…

Supermassive binary black holes (BBHs) are unavoidable products of galaxy mergers and are expected to exist in the cores of many quasars. Great effort has been made during the past several decades to search for BBHs among quasars; however,…

Gravitational lensing of gravitational waves (GWs) is a powerful probe of the matter distribution in the universe. Here we revisit the wave-optics effects induced by dark matter (DM) halos on the GW signals of merging massive black hole…

The bright gamma-ray blazar S5 1044+71 has been identified as showing very significant quasi-periodic oscillations in the Fermi-LAT data in recent studies, with a periodicity of about 3 years. With the completion of a new gamma-ray cycle,…

We propose a machine learning-based approach for parameter estimation of Massive Black Hole Binaries (MBHBs), leveraging normalizing flows to approximate the likelihood function. By training these flows on simulated data, we can generate…

While there has been an increase in interest in the possibility of quasi-periodic oscillations (QPOs) in blazars, the search has hitherto been restricted to sources with well-sampled light curves. Objects with light curves that include gaps…