Related papers: J2102+6015: a potential distant multimessenger?
The extremely high redshift (z=5.3) radio source SDSS J102623.61+254259.5 (J1026+2542) is among the most distant and most luminous radio-loud active galactic nuclei (AGN) known to date. Its one-sided radio jet structure on milli-arcsecond…
We present observational evidence for three massive, accreting black holes in the $z=5.0167$ galaxy J0148-4214 from JWST/NIRSpec-IFU spectroscopy. The black holes are revealed through broad H$\alpha$ emission (FWHM = 430-2920 km/s) without…
We have selected SDSS J222032.50+002537.5 and SDSS J142048.01+120545.9 as best blazar candidates out of a complete sample of extremely radio-loud quasars at z>4, with highly massive black holes. We observed them and a third serendipitous…
The peculiar QSO J0927+2943 shows multiple sets of emission lines in its optical spectrum. This signature has been interpreted as the relative motion between a black hole, either recoiling or bound in a binary system, and its host galaxy,…
We demonstrate that very massive (>10^8\msun), cosmologically nearby (z<1) black hole binaries (MBHBs), which are primary targets for ongoing and upcoming pulsar timing arrays (PTAs), are particularly appealing multimessenger carriers.…
The X-ray transient MAXI J1659-152 was discovered by Swift/BAT and it was initially identified as a GRB. Soon its Galactic origin and binary nature were established. There exists a wealth of multi-wavelength monitoring data for this source,…
We report the discovery of peculiar features in the optical spectrum of 4C+22.25, a flat spectrum radio quasar at z=0.4183 observed in the SDSS and in a dedicated spectroscopic follow-up from the Nordic Optical Telescope. The Hbeta and…
We identify SDSS J153636.22+044127.0, a QSO discovered in the Sloan Digital Sky Survey, as a promising candidate for a binary black hole system. This QSO has two broad-line emission systems separated by 3500 km/sec. The redder system at…
We present a new type of observation relating the gravitational wave emission of supermassive black hole mergers to their electromagnetic counterparts. This dual emission involves variability of a relativistic jet arising from the…
In this paper we provide a short overview of the scope and strong future potential of a multi-messenger approach to gravitational-wave astronomy, that seeks to optimally combine gravtitational wave and electromagnetic observations. We…
We previously reported a putative detection of a radio galaxy at z=10.15, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The redshift of this source, GLEAM J0917-0012, was based upon three…
The search and study of close pairs of supermassive black holes (SMBHs) is important in the study of galaxy mergers which can possibly trigger active galactic nucleus (AGN) activity, and in the context of their evolution into the…
We present multifrequency Very Long Baseline Array (VLBA) observations of J16021+3326. These observations, along with variability data obtained from the Owens Valley Radio Observatory (OVRO) candidate gamma-ray blazar monitoring program,…
We present Hubble Space Telescope Wide Field Camera 3 photometric and grism observations of the candidate ultra-high-redshift (z>7) radio galaxy, GLEAM J0917-0012. This radio source was selected due to the curvature in its 70-230 MHz,…
Few high-redshift, radio-loud quasars are known to date. The extremely luminous, radio-bright quasar, SDSS J013127.34-032100.1 was recently discovered at a redshift of $z=5.18$. We observed the source with high resolution very long baseline…
We recently discovered the X-ray/optical outbursting source 3XMM J215022.4-055108. It was best explained as the tidal disruption of a star by an intermediate-mass black hole of mass of a few tens of thousand solar masses in a massive star…
Coalescing massive black hole binaries are powerful emitters of gravitational waves, in the LISA sensitivity range for masses M_BH ~ 10^{4-7} M_sun. According to hierarchical galaxy merger models, binary black holes should form frequently,…
Supermassive black hole binary systems (SMBHBs) are thought to emit the recently discovered nHz gravitational wave background; however, not a single individual nHz source has been confirmed to date. Long-term radio-monitoring at the Owens…
High-redshift binary quasars provide key insights into mergers and quasar activity, and are useful tools for probing the spatial kinematics and chemistry of galaxies along the line-of-sight. However, only three sub-10-kpc binaries have been…
SWIFT J1626.6-5156 is an X-ray pulsar that was discovered in December 2005 during an X-ray outburst. Although the X-ray data suggest that the system is a high-mass X-ray binary, very little information exists on the nature of the optical…