28 research outputs found
Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane
Motivated by the large body of literature around the phenomenological
properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in
the radio:X-ray luminosity plane, we carry out a comparative regression
analysis on 36 BHs and 41 NSs in hard X-ray states, with data over 7 dex in
X-ray luminosity for both. The BHs follow a radio to X-ray (logarithmic)
luminosity relation with slope , consistent with the NSs'
slope () within 2.5. The best-fitting
intercept for the BHs significantly exceeds that for the NSs, cementing BHs as
more radio loud, by a factor 22. \This discrepancy can not be fully
accounted for by the mass or bolometric correction gap, nor by the NS boundary
layer contribution to the X-rays, and is likely to reflect physical differences
in the accretion flow efficiency, or the jet powering mechanism. Once
importance sampling is implemented to account for the different luminosity
distributions, the slopes of the non-pulsating and pulsating NS subsamples are
formally inconsistent (), unless the transitional millisecond pulsars
(whose incoherent radio emission mechanism is not firmly established) are
excluded from the analysis. We confirm the lack of a robust partitioning of the
BH data set into separate luminosity tracks.Comment: Accepted by MNRAS as a Lette
Expectations for Fast Radio Bursts in Neutron Star-Massive Star binaries
Recent observations of a small sample of repeating Fast Radio Bursts (FRBs)
have revealed a periodicity in their bursting activity that may be suggestive
of a binary origin for the modulation. We set out to explore the scenario where
a subset of repeating FRBs originates in binary systems hosting a highly
energetic neutron star and a massive companion star, akin to -ray
binaries and young High-Mass X-ray Binaries. Firstly, we specifically focus on
the host galaxy properties and binary formation rates. Subsequently, we
investigate the expected evolution of the rotation and dispersion measure in
this scenario, the predicted birth-site offsets, and the origin of the
persistent radio emission observed in a subset of these systems. The host
galaxies for repeating FRBs favour the formation of neutron star-massive star
binary systems but any conclusive evidence will require future discoveries and
localizations of FRBs. The birth rate of high-mass X-ray binaries, used as a
proxy for all considered binaries, significantly exceeds the estimated rate of
FRBs, which can be explained if only a small subset of these systems produce
FRBs. We show that under simple assumptions, we can reproduce the DM and RM
evolution that is seen in a subset of repeating FRBs. We also discuss the
possibility of detecting a persistent radio source associated with the FRB due
to an intra-binary shock between companion star wind and either the pulsar wind
or giant magnetar flares. The observed long-term luminosity stability of the
Persistent Radio Sources is most consistent with a giant flare-powered
scenario. However, this explanation is highly dependent on the magnetic field
properties of the neutron star. With these explorations, we have aimed to
provide a framework to discuss future FRB observations in the context of
neutron star-massive star binary scenarios.Comment: 15 pages, 7 figures, 2 appendices, accepted for publication in A&A.
Abstract truncated to fit the word limit on arXi
A systematic study of the phase difference between QPO harmonics in black hole X-ray binaries
We perform a systematic study of the evolution of the waveform of black hole
X-ray binary low-frequency QPOs, by measuring the phase difference between
their fundamental and harmonic features. This phase difference has been studied
previously for small number of QPO frequencies in individual sources. Here, we
present a sample study spanning fourteen sources and a wide range of QPO
frequencies. With an automated pipeline, we systematically fit power spectra
and calculate phase differences from archival Rossi X-ray Timing Explorer
(RXTE) observations. We measure well-defined phase differences over a large
range of QPO frequencies for most sources, demonstrating that a QPO for a given
source and frequency has a persistent underlying waveform. This confirms the
validity of recently developed spectral-timing methods performing phase
resolved spectroscopy of the QPO. Furthermore, we evaluate the phase difference
as a function of QPO frequency. For Type-B QPOs, we find that the phase
difference stays constant with frequency for most sources. We propose a simple
jet precession model to explain these constant Type-B QPO phase differences.
The phase difference of the Type-C QPO is not constant but systematically
evolves with QPO frequency, with the resulting relation being similar for a
number of high inclination sources, but more variable for low-inclination
sources. We discuss how the evolving phase difference can naturally arise in
the framework of precession models for the Type-C QPO, by considering the
contributions of a direct and reflected component to the QPO waveform
The Link Between Neutron Star X-ray Binaries and Spider Pulsars
The discovery of transitional millisecond pulsars (tMSPs) provided conclusive
proof that neutron star (NS) low-mass X-ray binaries (LMXBs) comprise part of
the evolutionary pathway towards binary millisecond pulsars (MSPs). Redback and
black widow `spider' pulsars are a sub-category of binary MSPs that `devour'
their companions through ablation - the process through which material is
lifted from the stellar surface by a pulsar wind. In addition to reducing the
companion star's mass, ablation introduces observable characteristics like
extended, energy-dependent and asymmetric eclipse profiles in systems observed
at a sufficiently high inclination. Here, we present a detailed study and
comparison of the X-ray eclipses of two NS LMXBs;
J1858.60814 and EXO 0748676. Some of the X-ray eclipse characteristics
observed in these two LMXBs are similar to the radio eclipse characteristics of
eclipsing redback and black widow pulsars, suggesting that they may also host
ablated companion stars. X-ray irradiation or a pulsar wind could drive the
ablation. We conduct orbital phase-resolved spectroscopy for both LMXBs to map
the column density, ionization and covering fraction of the material outflow.
From this, we infer the presence of highly ionized and clumpy ablated material
around the companion star in both systems. We term LMXBs undergoing ablation,
, and speculate that they may be the progenitors of
redback pulsars under the assumption that ablation begins in the LMXB stage.
Therefore, the false widows could provide a link between LMXBs and spider
pulsars. The detection of radio pulsations during non-accreting states can
support this hypothesis.Comment: 21 pages, 15 figures. Accepted for publication in MNRAS. The full
version of Table 1 is available as online supplementary material from the
MNRAS websit
Accretion spin-up and a strong magnetic field in the slow-spinning Be X-ray binary MAXI J0655-013
We present MAXI and NuSTAR observations of the Be X-ray binary, MAXI
J0655-013, in outburst. NuSTAR observed the source once early in the outburst,
when spectral analysis yields a bolometric (0.1--100 keV), unabsorbed source
luminosity of , and a
second time 54 days later, by which time the luminosity dropped to
after first undergoing
a dramatic increase. Timing analysis of the NuSTAR data reveals a neutron star
spin period of s during the first observation, which decreased
to s by the time of the second observation, indicating spin-up due
to accretion throughout the outburst. Furthermore, during the first NuSTAR
observation, we observed quasiperiodic oscillations with centroid frequency
mHz, which exhibited a second harmonic feature. By combining the
MAXI and NuSTAR data with pulse period measurements reported by Fermi/GBM, we
are able to show that apparent flaring behavior in the MAXI light-curve is an
artifact introduced by uneven sampling of the pulse profile, which has a large
pulsed fraction. Finally, we estimate the magnetic field strength at the
neutron star surface via three independent methods, invoking a tentative
cyclotron resonance scattering feature at keV, QPO production at the inner
edge of the accretion disk, and spin-up via interaction of the neutron star
magnetic field with accreting material. Each of these result in a significantly
different value. We discuss the strengths and weaknesses of each method and
infer that MAXI J0655-013 is likely to have a high surface magnetic field
strength, G.Comment: 19 pages, 10 figure, 4 tables; submitted to ApJ on May 24, 202
A shared accretion instability for black holes and neutron stars
Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales2. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole3,4,5. Although there are hints of these cycles in a few isolated cases6,7,8,9,10, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle11. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrumâfrom radio to X-rayâof both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.The authors thank the referees for the constructive comments which improved the manuscript. The interpretation of the FV thank R. Arcodia, P. Casella, G. Marcel, G. Mastroserio, N. Scepi and L. Stella for insightful discussions. The interpretation of the results benefited from discussions held during the meeting âLooking at the disc-jet coupling from different anglesâ held at the International Space Science Institute in Bern, Switzerland. FV was supported by the NASA awards 80NSSC19K1456, 80NSSC21K0526 and from grant FJC2020-043334-I financed by MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR. JN acknowledges support by the SAO award GO1-22036X. AJT acknowledges support for this work was provided by NASA through the NASA Hubble Fellowship grant #HSTâHF2â51494.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5â26555. D.A. and N.C.S. acknowledges support from the Science and Technology Facilities Council (STFC) grant ST/V001000/1. FV, MAP and VC acknowledge support from the Spanish Ministry of Science and Innovation research project PID2020-120323GB-I00. MAP acknowledges support from the ConsejerĂa de EconomĂa, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2021010132 ACCISI/FEDER, UE. TMB acknowledges financial contribution from the agreement ASI-INAF n.2017- 14-H.0 and from PRIN-INAF 2019 N.15. TMD acknowledges support from the Spanish Ministry of Science and Innovation project PID2021-124879NB-I00, and the Europa Excelencia grant (EUR2021-122010). TDR acknowledge financial contribution from the agreement ASIINAF n.2017-14-H.0.Peer ReviewedPostprint (author's final draft
Evidence for a dynamic corona in the short-term time lags of black hole X-ray binary MAXI J1820+070
In X-ray observations of hard state black hole X-ray binaries, rapid
variations in accretion disc and coronal power-law emission are correlated and
show Fourier-frequency-dependent time lags. On short (~0.1 s) time-scales,
these lags are thought to be due to reverberation and therefore may depend
strongly on the geometry of the corona. Low-frequency quasi-periodic
oscillations (QPOs) are variations in X-ray flux that have been suggested to
arise because of geometric changes in the corona, possibly due to General
Relativistic Lense-Thirring precession. Therefore one might expect the
short-term time lags to vary on the QPO time-scale. We performed novel
spectral-timing analyses on NICER observations of the black hole X-ray binary
MAXI J1820+070 during the hard state of its outburst in 2018 to investigate how
the short-term time lags between a disc-dominated and a coronal
power-law-dominated energy band vary on different time-scales. Our method can
distinguish between variability due to the QPO and broadband noise, and we find
a linear correlation between the power-law flux and lag amplitude that is
strongest at the QPO frequency. We also introduce a new method to resolve the
QPO signal and determine the QPO-phase-dependence of the flux and lag
variations, finding that both are very similar. Our results are consistent with
a geometric origin of QPOs, but also provide evidence for a dynamic corona with
a geometry varying in a similar way over a broad range of time-scales, not just
the QPO time-scale.Comment: 19 pages, 14 figures, 3 tables, accepted for publication in MNRA
X-Ray and Radio Monitoring of the Neutron Star Low-mass X-Ray Binary 1A 1744-361: Quasiperiodic Oscillations, Transient Ejections, and a Disk Atmosphere
We report on X-ray (NICER/NuSTAR/MAXI/Swift) and radio (MeerKAT) timing and spectroscopic analysis from a 3 month monitoring campaign in 2022 of a high-intensity outburst of the dipping neutron star low-mass X-ray binary 1A 1744â361. The 0.5â6.8 keV NICER X-ray hardnessâintensity and colorâcolor diagrams of the observations throughout the outburst suggest that 1A 1744â361 spent most of its outburst in an atoll-state, but we show that the source exhibited Z-state-like properties at the peak of the outburst, similar to a small sample of other atoll-state sources. A timing analysis with NICER data revealed several instances of an â8 Hz quasiperiodic oscillation (QPO; fractional rms amplitudes of âŒ5%) around the peak of the outburst, the first from this source, which we connect to the normal branch QPOs seen in the Z-state. Our observations of 1A 1744â361 are fully consistent with the idea of the mass accretion rate being the main distinguishing parameter between atoll- and Z-states. Radio monitoring data by MeerKAT suggests that the source was at its radio-brightest during the outburst peak, and that the source transitioned from the âislandâ spectral state to the âbananaâ state within âŒ3 days of the outburst onset, launching transient jet ejecta. The observations present the strongest evidence for radio flaring, including jet ejecta, during the island-to-banana spectral state transition at low accretion rates (atoll-state). The source also exhibited Fe xxv, Fe xxvi Kα, and KÎČ X-ray absorption lines, whose origins likely lie in an accretion disk atmosphere
First detection of X-ray polarization from the accreting neutron star 4U 1820-303
This paper reports the first detection of polarization in the X-rays for
atoll-source 4U 1820-303, obtained with the Imaging X-ray Polarimetry Explorer
(IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements
were also performed in the radio with the Australia Telescope Compact Array
(ATCA). The IXPE observations of 4U 1820-303 were coordinated with Swift-XRT,
NICER, and NuSTAR aiming to obtain an accurate X-ray spectral model covering a
broad energy interval. The source shows a significant polarization above 4 keV,
with a polarization degree of 2.0(0.5)% and a polarization angle of -55(7) deg
in the 4-7 keV energy range, and a polarization degree of 10(2)% and a
polarization angle of -67(7) deg in the 7-8 keV energy bin. This polarization
also shows a clear energy trend with polarization degree increasing with energy
and a hint for a position-angle change of about 90 deg at 96% CL around 4 keV.
The spectro-polarimetric fit indicates that the accretion disk is polarized
orthogonally to the hard spectral component, which is presumably produced in
the boundary/spreading layer. We do not detect linear polarization from the
radio counterpart, with a 99.97% upper limit of 50% at 7.25 GHz
jvandeneijnden/LSV44_17_RepPackage: Published version
Reproduction Package for "VLA monitoring of LS V +44 17 reveals scatter in the X-ray -- radio correlation of Be/X-ray binaries