Conveners
Broadband Spectroscopy (modelling and observation)
- Nick Kylafis (Institute of Astrophysics, FORTH, Crete)
Broadband Spectroscopy (modelling and observation)
- Melania Del Santo (Istituto Nazionale di Astrofisica (INAF))
Broadband Spectroscopy (modelling and observation)
- Melania Del Santo (Istituto Nazionale di Astrofisica (INAF))
I will present an overview of broadband spectral data for microquasar systems, with a focus on black hole X-ray binaries. In particular, I will describe different broadband X-ray spectral data sets which are fitted to infer properties of the disk, corona, and/or jet, including e.g., the accretion geometry or black-hole spin. I will discuss the connection of X-ray spectra to other...
Microquasars, with their complex interplay of accretion disks, relativistic jets, and coronae, emit across the electromagnetic spectrum. This talk will review the ongoing attempts to perform broadband, radio to gamma-ray, spectral decomposition in microquasars. I will summarise the key observables that help us distinguishing between different spectral models and physical components.
4U 1630-47 is a peculiar transient X-ray binary believed to host a black hole as its compact object. Its behavior differs from that of other BH-XRBs, as it shows recurrent outbursts with a fairly regular recurrence period and lacks bright hard states. In contrast, its soft-state spectra above 10 keV are characterized by a strong power-law component extending up to 200 keV without any...
I will present the results of a unique multi-wavelength campaign focused on the recently discovered black-hole transient Swift J1727. This system exhibited the brightest X-ray source in the sky ever observed, and it was the first to be observed with the X-ray polarimeter (IXPE) throughout an entire outburst. Our observations covered simultaneously the full frequency range from X-ray to radio...
Outbursts from transient Low-Mass X-ray Binaries (LMXBs) have been historically caught by All-Sky X-ray monitors at relatively high X-ray luminosities, i.e. above ~1e36 erg/s; observations of these sources during the early rise of the outbursts, the stage where the X-ray luminosity increases by three or more orders of magnitude with respect to the quiescence regime, have been so far very...
MAXI J1348-630 is a black hole X-ray transient discovered in January 2019 that underwent a reflare and several mini-outbursts at the end of its main outburst. In this talk, we present the first multiwavelength study of the system during outburst, reflare and mini-outbursts based on the long-term optical monitoring of the system with the Las Cumbres Observatory (LCO) network. The full optical...
In recent years, spins of merging black holes have been relatively accurately measured based on their gravitational-wave signals. Their are generally low, with the estimated average effective spin parameter as low as 0.06. On the other hand, spins of many accreting black-hole binaries have been measured to be high, some close to the maximum spin parameter of 1, e.g. greater than 0.9985 at 3...
The geometry and physical conditions of black hole accretion discs are expected to change dramatically as a function of mass accretion rate and the resulting X-ray luminosity. Theoretical models predict that these changes become particularly relevant as the luminosity approaches the Eddington limit (LEdd), a regime where the standard thin-disc solution is thought to break down in...
The irradiation of the innermost accretion disk by X-rays emitted by the corona produces characteristic reflection features. Besides depending on the density and ionization of the disk itself, also the spin of the black hole and the corona itself is imprinted on the reflection spectrum due to strong relativistic effects. When fitting observational data of black hole X-ray binaries and AGN,...
The 2023/24 NICER monitoring campaign of the 7 Crab bright black hole X-ray binary Swift J1727.8-1613 covered the outburst in almost all states. High-quality data are available in the high-Eddington-fraction bright hard state, the soft intermediate state, the soft state decay, and the poorly understood back-transition into the dim hard state, making it an ideal dataset to compare the accretion...
The geometry of the accretion flow around accreting black holes is highly variable and remains highly unconstrained. In their hard states, the X-ray spectrum is dominated by a hot inflow located above or within the accretion disk. Conversely, in their soft states, the spectrum is dominated by soft emission from the geometrically thin accretion disk. The geometry of the hot inflow and its...
X-ray reflection spectroscopy is a powerful tool to study the accretion geometry near black holes and spacetime properties. The spirit of this method is to study the reprocessed corona emission by the cold accretion disk that extends close to the black hole. Previous X-ray reflection models consider a disk density of 10^-15 cm^-3, which is only appropriate for very massive black holes (> 10^7...
Bayesian analysis has begun to be more widely adopted in X-ray spectroscopy, but it has largely been constrained to relatively simple physical models due to limitations in X-ray modelling software and computation time. As a result, Bayesian analysis of numerical models with high physics complexity have remained out of reach. This is a challenge, for example when modelling the X-ray emission of...
The X-ray flux from black hole X-ray binaries in the hard state is highly variable on a broad range of timescales. On a timescale of seconds, such broadband noise is thought to arise in the turbulent accretion disk and propagated to the corona, which emits harder X-rays in the spectral shape of a powerlaw with a cut-off. The nature and geometry of the corona is subject to debate, but there is...
I will present results from a coordinated spectral study of the black hole X-ray binary GX 339–4 during its 2021 outburst, capturing its transition from the hard to soft accretion state. Using simultaneous observations from NuSTAR, NICER, and Insight–HXMT, we applied relativistic reflection models to track changes in the accretion disk, particularly the inner disk radius (𝑅𝑖𝑛). Interestingly,...
GX 339–4 is a low-mass X-ray binary often used as an archetype, showing typical source behaviors. The source undergoes a full outburst every 2-3 years, passing through all known accretion
states. The 2023-2024 outburst was monitored as part of a multiwavelength campaign, which
included X-ray observations by IXPE and NICER. We
used NICER data to analyze the spectral-timing properties of GX...
The wealth and complexity of X-ray data provided by modern observatories has seen a dramatic improvement in recent years, in part due to new facilities like NICER and IXPE. This trend will accelerate further with new techniques like polarimetry timing, as well as future missions like eXTP and Athena. On the other hand, the software modelling tools utilized by the community to model spectral...
The BHB GRS~1915+105 was bright for 26 years since its discovery and is well known for its disk instabilities, quasi-periodic oscillations, and disk wind signatures. We report a long-term spectral-timing tracing of this source from mid-2017 until the onset of the so-called obscured state based on the complete data from NICER and other potential X-ray missions. In the soft state predating 2018,...
