Abstract
Over the past decade, observations of relativistic outflows from outbursting X-ray binaries in the Galactic field have grown significantly. In this work, we present the first detection of ...moving and decelerating radio-emitting outflows from an X-ray binary in a globular cluster. MAXI J1848−015 is a recently discovered transient X-ray binary in the direction of the globular cluster GLIMPSE-C01. Using observations from the Karl G. Jansky Very Large Array, and a monitoring campaign with the MeerKAT observatory for 500 days, we model the motion of the outflows. This represents some of the most intensive, long-term coverage of relativistically moving X-ray binary outflows to date. We use the proper motions of the outflows from MAXI J1848−015 to constrain the component of the intrinsic jet speed along the line of sight,
β
int
cos
θ
ejection
, to be =0.19 ± 0.02. Assuming it is located in GLIMPSE-C01, at 3.4 kpc, we determine the intrinsic jet speed,
β
int
= 0.79 ± 0.07, and the inclination angle to the line of sight,
θ
ejection
= 76° ± 2°. This makes the outflows from MAXI J1848−015 somewhat slower than those seen from many other known X-ray binaries. We also constrain the maximum distance to MAXI J1848−015 to be 4.3 kpc. Finally, we discuss the implications of our findings for the nature of the compact object in this system, finding that a black hole primary is a viable (but as-of-yet unconfirmed) explanation for the observed properties of MAXI J1848−015. If future data and/or analysis provide more conclusive evidence that MAXI J1848−015 indeed hosts a black hole, it would be the first black hole X-ray binary in outburst identified in a Galactic globular cluster.
We present the results of an intensive multi-epoch radio frequency campaign on the energetic and nearby GRB 171010A with the Karl G. Janksy Very Large Array and Arcminute Microkelvin Imager Large ...Array. We began observing GRB 171010A a day after its initial detection, and were able to monitor the temporal and spectral evolution of the source over the following weeks. The spectra and their evolution are compared to the canonical theories for broad-band GRB afterglows, with which we find a general agreement. There are, however, a number of features that are challenging to explain with a simple forward shock model, and we discuss possible reasons for these discrepancies. This includes the consideration of the existence of a reverse shock component, potential microphysical parameter evolution, and the effect of scintillation.
The adhesion ability of bacteria to abiotic surfaces has important implications in food industries, because these organisms can survive for long periods through the biofilm formation. They can be ...transferred from one place to another in the industry causing contamination of the food processing environment. In this study, the antibacterial and antibiofilm activities of the antimicrobial peptide P34, characterized as a bacteriocin-like substance (BLS P34) were tested against planktonic and sessile cells of Staphylococcus aureus and Enterococcus faecalis isolated from foods. The BLS P34 showed inhibitory effect against all planktonic cells of E. faecalis. The inhibition of biofilm formation and the eradication of pre-formed biofilm were evaluated with the crystal violet assay and with the reduction of 3-bromide 4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium. The BLS P34 promoted a reduction of percentage of adhered microbial cells on the surface, not being able to perform the complete elimination of biofilm formation. The metabolic activity of S. aureus biofilms decreased considerably between 41-95%. However, E. faecalis cells showed up metabolically stimulated. The BLS P34 has the potential antibiofilm for the species S. aureus. Studies suggest more detailed approaches to a better understanding of the interactions between the antimicrobial and bacterial cells within the biofilm structure.
ABSTRACT The radio–X-ray correlation that characterizes accreting black holes at all mass scales – from stellar mass black holes in binary systems to supermassive black holes powering active galactic ...nuclei – is one of the most important pieces of observational evidence supporting the existence of a connection between the accretion process and the generation of collimated outflows – or jets – in accreting systems. Although recent studies suggest that the correlation extends down to low luminosities, only a handful of stellar mass black holes have been clearly detected, and in general only upper limits (especially at radio wavelengths) can be obtained during quiescence. We recently obtained detections of the black hole X-ray binary (XRB) GX 339–4 in quiescence using the Meer Karoo Array Telescope (MeerKAT) radio telescope and Swift X-ray Telescope instrument on board the Neil Gehrels Swift Observatory, probing the lower end of the radio–X-ray correlation. We present the properties of accretion and of the connected generation of jets in the poorly studied low-accretion rate regime for this canonical black hole XRB system.
ABSTRACT
Black hole (BH) low mass X-ray binaries in their hard spectral state are found to display two different correlations between the radio emission from the compact jets and the X-ray emission ...from the inner accretion flow. Here, we present a large data set of quasi-simultaneous radio and X-ray observations of the recently discovered accreting BH MAXI J1348–630 during its 2019/2020 outburst. Our results span almost six orders of magnitude in X-ray luminosity, allowing us to probe the accretion–ejection coupling from the brightest to the faintest phases of the outburst. We find that MAXI J1348–630 belongs to the growing population of outliers at the highest observed luminosities. Interestingly, MAXI J1348–630 deviates from the outlier track at LX ≲ 7 × 1035(D/2.2 kpc)2 erg s−1 and ultimately rejoins the standard track at LX ≃ 1033(D/2.2 kpc)2 erg s−1, displaying a hybrid radio/X-ray correlation, observed only in a handful of sources. However, for MAXI J1348–630 these transitions happen at luminosities much lower than what observed for similar sources (at least an order of magnitude). We discuss the behaviour of MAXI J1348–630 in light of the currently proposed scenarios and highlight the importance of future deep monitorings of hybrid correlation sources, especially close to the transitions and in the low luminosity regime.
ABSTRACT In recent years, the black hole candidate X-ray binary system H1743−322 has undergone outbursts and it has been observed with X-ray and radio telescopes. We present 1.3 GHz MeerKAT radio ...data from the ThunderKAT Large Survey Project on radio transients for the 2018 outburst of H1743−322. We obtain seven detections from a weekly monitoring programme and use publicly available Swift X-ray Telescope and Monitor of All-sky X-ray Image data to investigate the radio/X-ray correlation of H1743−322 for this outburst. We compare the 2018 outburst with those reported in the literature for this system and find that the X-ray outburst reported is similar to previously reported ‘hard-only’ outbursts. As in previous outbursts, H1743−322 follows the ‘radio-quiet’ correlation in the radio/X-ray plane for black hole X-ray binaries, and the radio spectral index throughout the outburst is consistent with the ‘radio-quiet’ population.
Context.
X-ray binaries in outburst typically show two canonical X-ray spectral states (i.e., hard and soft states), as well as different intermediate states, in which the physical properties of the ...accretion flow are known to change. However, the truncation of the optically thick disk and the geometry of the optically thin accretion flow (corona) in the hard state are still debated. Recently, the JED-SAD paradigm has been proposed for black hole X-ray binaries, aimed at addressing the topic of accretion and ejection and their interplay in these systems. According to this model, the accretion flow is composed of an outer standard Shakura-Sunyaev disk (SAD) and an inner hot jet emitting disk (JED). The JED produces both hard X-ray emission, effectively playing the role of the hot corona, and radio jets. The disruption of the JED at the transition to the soft state coincides with the quenching of the jet.
Aims.
In this paper we use the JED-SAD model to describe the evolution of the accretion flow in the black hole transient MAXI J1820+070 during its hard and hard-intermediate states. Unlike the previous applications of this model, the Compton reflection component has been taken into account.
Methods.
We use eight broadband X-ray spectra, including
NuSTAR
, NICER, and the
Neil Gehrels Swift
Observatory data, providing a total spectral coverage of 0.8–190 keV. The data were directly fitted with the JED-SAD model. We performed the procedure twice, considering two different values for the innermost stable circular orbit (ISCO): 4
R
G
(
a
*
= 0.55) and 2
R
G
(
a
*
= 0.95).
Results.
Our results suggest that the optically thick disk (the SAD) does not extend down to the ISCO in any of the considered epochs. In particular, assuming
R
ISCO
= 4
R
G
, as the system evolves toward the transitional hard-intermediate state, we find an inner radius within a range of ∼60
R
G
in the first observation down to ∼30
R
G
in the last one. The decrease of the inner edge of the SAD is accompanied by an increase in the mass-accretion rate. However, when we assume
R
ISCO
= 2 we find that the mass accretion rate remains constant and the evolution of the accretion flow is driven by the decrease in the sonic Mach number
m
S
, which is unexpected. In all hard–intermediate state observations, two reflection components, characterized by different values of ionization, are required to adequately explain the data. These components likely originate from different regions of the SAD.
Conclusions.
The analysis performed provides a coherent physical evolution of the accretion flow in the hard and hard-intermediate states and supports a truncated disk scenario. We show that a flared outer disk could, in principle, explain the double reflection component. The odd results obtained for
R
ISCO
= 2
R
G
can also be considered as further evidence that MAXI J1820+070 harbors a moderately spinning black hole, as suggested in other works.
ABSTRACT
We present the results of a weekly monitoring of the new black hole candidate X-ray binary MAXI J1631-472 carried out with the MeerKAT radio interferometer, the Neil Gehrels Swift ...Observatory, and the Monitor of All-sky X-ray Image (MAXI) instrument, during its 2018–2019 outburst. The source exhibits a number of X-ray states, in particular both high- and low-luminosity hard states bracketed by extended soft states. Radio flaring is observed shortly after a transition from hard/intermediate states to the soft state. This is broadly in agreement with existing empirical models, but its extended duration hints at multiple unresolved flares and/or jet–ISM interactions. In the hard state radio:X-ray plane, the source is revealed to be ‘radio quiet’ at high luminosities, but to rejoin the ‘standard’ track at lower luminosities, an increasingly common observed pattern of behaviour.
ABSTRACT
The black hole transient GRS 1716−249 was monitored from the radio to the γ-ray band during its 2016–2017 outburst. This paper focuses on the spectral energy distribution (SED) obtained in ...2017 February–March, when GRS 1716−249 was in a bright hard spectral state. The soft γ-ray data collected with the INTEGRAL/SPI telescope show the presence of a spectral component that is in excess of the thermal Comptonization emission. This component is usually interpreted as inverse Compton emission from a tiny fraction of non-thermal electrons in the X-ray corona. We find that hybrid thermal/non-thermal Comptonization models provide a good fit to the X-/γ-ray spectrum of GRS 1716−249. The best-fitting parameters are typical of the bright hard state spectra observed in other black hole X-ray binaries. Moreover, the magnetized hybrid Comptonization model belm provides an upper limit on the intensity of the coronal magnetic field of about 106 G. Alternatively, this soft γ-ray emission could originate from synchrotron emission in the radio jet. In order to test this hypothesis, we fit the SED with the irradiated disc plus Comptonization model combined with the jet internal shock emission model ishem. We found that a jet with an electron distribution of p ≃ 2.1 can reproduce the soft γ-ray emission of GRS 1716−249. However, if we introduce the expected cooling break around 10 keV, the jet model can no longer explain the observed soft γ-ray emission, unless the index of the electron energy distribution is significantly harder (p < 2).
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