Related papers: The stringent upper limit on jet power in the pers…
Recent work on the engines of active galactic nuclei jets suggests their power depends strongly and perhaps counter-intuitively on black hole spin. We explore the consequences of this on the radio-loud population of active galactic nuclei…
We have obtained simultaneous optical and near infrared observations of 4U 1543-47 during its 2002 outburst. The most striking feature of the outburst light curve is the secondary maximum which appears after the object transitions into the…
Approximately 10-20% of Active Galactic Nuclei are known to eject powerful jets from the innermost regions. There is very little observational evidence if the jets are powered by spinning black holes and if the accretion disks extend to the…
We present an analysis of a short NuSTAR observation of the stellar-mass black hole and low-mass X-ray binary 4U 1630$-$472. Reflection from the inner accretion disk is clearly detected for the first time in this source, owing to the…
While the non-thermal radio through at least near-infrared emission in the hard state in X-ray binaries (XRBs) is known to originate in jets, the source of the non-thermal X-ray component is still uncertain. We introduce a new model for…
NICER observed two outbursts from the neutron star low-mass X-ray binary 4U~1730$-$22 in 2021 and 2022, which showed a similar spectral evolution in the hardness-intensity diagram. Seventeen type I X-ray bursts were identified in both…
Models of jet production in black hole systems suggest that the properties of the accretion disk - such as its mass accretion rate, inner radius, and emergent magnetic field - should drive and modulate the production of relativistic jets.…
Ser X-1 is a low mass neutron star X-ray binary and has been persistently accreting since its discovery in the 1960s. It has always been observed to be in a soft spectral state and has never showed substantial long-term X-ray variability.…
Accreting stellar-mass black holes appear to populate two branches in a radio:X-ray luminosity plane. We have investigated the X-ray variability properties of a large number of black hole low-mass X-ray binaries, with the aim of unveiling…
We present the results of the first X-ray polarimetric observation of the low-mass X-ray binary 4U 1957+115, performed with the Imaging X-ray Polarimetry Explorer in May 2023. The binary system has been in a high-soft spectral state since…
We have observed the black hole candidate X-ray binary GX 339-4 at radio wavelengths before, during and after the 1998 high/soft X-ray state transition. We find that the radio emission from the system is strongly correlated with the hard…
We discovered a periodicity at about 8.7s from the X--ray sources 4U0142+61, previously considered a possible black hole candidate on the basis of its ultrasoft spectrum. The pulsations are visible only in the 1--4 keV energy range, during…
The black hole X-ray binary MAXI J1820$+$070 began its first recorded outburst in March 2018, and remained an active radio, X-ray, and optical source for over four years. Due to the low distance to the source and its intrinsically high…
We report on X-ray and radio observations of the ultra-compact X-ray binary 4U 1543-624 taken in August 2017 during an enhanced accretion episode. We obtained NICER monitoring of the source over a $\sim10$ day period during which…
We present the analysis of six {\it Chandra} X-ray high-resolution observations of the black hole low-mass X-ray binary 4U~1630-47 taken during its 2012-2013 outburst. {\rm Fe}~{\sc XXVI} K$\alpha$, K$\beta$, {\rm Fe}~{\sc XXV} K$\alpha$,…
we propose a jet model for the low/hard state of black-hole X-ray sources which explains a) the X-ray spectra, b) the timelag spectra, c) the increase in the amplitude (QPO and high frequency) with increasing photon energy, and d) the…
Relativistic discrete ejecta launched by black hole X-ray binaries (BH XRBs) can be observed to propagate up to parsec-scales from the central object. Observing the final deceleration phase of these jets is crucial to estimate their…
4U 1630-472 is a recurrent X-ray transient classified as a black-hole candidate from its spectral and timing properties. One of the peculiarities of this source is the presence of regular outbursts with a recurrence period between 600 and…
The ultracompact X-ray binary 4U 1820-30 is well known for its ~170-d superorbital modulation in X-ray flux and spectrum, and the exclusiveness of bursting behavior to the low hard 'island' state. In May-June 2009, there was an…
Large energy-dependent X-ray polarization degree is detected by the Imaging X-ray Polarimetry Explorer ({IXPE}) in the high-soft emission state of the black hole X-ray binary 4U 1630--47. The highly significant detection (at…