scholarly journals The variable radio counterpart of Swift J1858.6-0814

2020 ◽  
Vol 496 (4) ◽  
pp. 4127-4140 ◽  
Author(s):  
J van den Eijnden ◽  
N Degenaar ◽  
T D Russell ◽  
D J K Buisson ◽  
D Altamirano ◽  
...  
Keyword(s):  
Time Scales ◽  
Radio Spectrum ◽  
Electromagnetic Spectrum ◽  
Very Large Array ◽  
X Ray ◽  
Geometric Origin ◽  
Optical Wavelengths ◽  
X Ray Binaries ◽  
Variable Radio

ABSTRACT Swift J1858.6-0814 is a transient neutron star X-ray binary discovered in 2018 October. Multiwavelength follow-up observations across the electromagnetic spectrum revealed many interesting properties, such as erratic flaring on minute time-scales and evidence for wind outflows at both X-ray and optical wavelengths, strong and variable local absorption, and an anomalously hard X-ray spectrum. Here, we report on a detailed radio observing campaign consisting of one observation at 5.5/9 GHz with the Australia Telescope Compact Array, and nine observations at 4.5/7.5 GHz with the Karl G. Jansky Very Large Array. A radio counterpart with a flat to inverted radio spectrum is detected in all observations, consistent with a compact jet being launched from the system. Swift J1858.6-0814 is highly variable at radio wavelengths in most observations, showing significant variability when imaged on 3-to-5-min time-scales and changing up to factors of 8 within 20 min. The periods of brightest radio emission are not associated with steep radio spectra, implying they do not originate from the launching of discrete ejecta. We find that the radio variability is similarly unlikely to have a geometric origin, be due to scintillation, or be causally related to the observed X-ray flaring. Instead, we find that it is consistent with being driven by variations in the accretion flow propagating down the compact jet. We compare the radio properties of SwiftJ1858.6-0814 with those of Eddington-limited X-ray binaries with similar X-ray and optical characteristics, but fail to find a match in radio variability, spectrum, and luminosity.

scholarly journals Variable Radio Emission from X-Ray Sources

1971 ◽  
Vol 15 ◽  
pp. 173-175 ◽  
Author(s):  
L. L. E. Braes ◽  
G. K. Miley
Keyword(s):  
Radio Emission ◽  
Aperture Synthesis ◽  
Electromagnetic Spectrum ◽  
Radio Telescopes ◽  
Low Resolution ◽  
X Ray ◽  
Synthesis Technique ◽  
Variable Radio

Dr. KELLOGG has just described some exciting new observations of X-ray sources made with the UHURU satellite. We shall now move some nine orders of magnitude in wavelength to the opposite end of the electromagnetic spectrum and report measurements of weak radio emission from some of the objects he mentioned. For the detection of weak sources most radio telescopes are not noise limited, but are confusion limited by their low resolution. The aperture synthesis technique minimizes this problem because it enables one to pinpoint the position of weak sources to the order of one second of arc.

scholarly journals Unveiling the Nature of INTEGRAL Objects: a Review

2014 ◽  
Vol 1 (1) ◽  
pp. 240-245
Author(s):  
Pietro Parisi
Keyword(s):  
Ir Spectroscopy ◽  
Energy Range ◽  
Southern Hemisphere ◽  
Cross Correlation ◽  
Active Galaxies ◽  
X Ray ◽  
The Real ◽  
Real Nature ◽  
X Ray Binaries

Since its launch in October 2002, the <em>INTEGRAL</em> observatory has improved our knowledge of the hard X-ray sky above 20 keV, carrying out more than ten years of observations in the energy range from 5 keV to 8 MeV. The most recently published <em>INTEGRAL</em>/IBIS surveys listed more than seven hundred sources in the 20-100 keV band. Most of these objects are either Active Galaxies (AGNs) or X-ray binaries; a fraction of both classes is made of highly absorbed sources, often associated with dim optical counterparts. Despite the big eort in the identication process, a large part of these IBIS objects (~25% of them) still remains unclassied. Cross-correlation with archival catalogues and/or multiwaveband follow-up observations are of invaluable help to identify and properly classify this unknown objects, but only optical or IR spectroscopy with ground based telescopes in the Northern and Southern Hemisphere can reveal the real nature of these objects. In this work we report on source types that we nd among the unidentied objects in the most recent <em>INTEGRAL</em> surveys.

scholarly journals Quasi-simultaneous Radio/X-Ray Observations of the Candidate Transitional Millisecond Pulsar 3FGL J1544.6−1125 during its Low-luminosity Accretion-disk State

2021 ◽  
Vol 923 (1) ◽  
pp. 3
Author(s):  
Amruta D. Jaodand ◽  
Adam T. Deller ◽  
Nina Gusinskaia ◽  
Jason W. T. Hessels ◽  
James C. A. Miller-Jones ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Array ◽  
Millisecond Pulsar ◽  
Very Large Array ◽  
X Ray ◽  
Upper Limit ◽  
5 Ghz ◽  
Variable Radio

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

scholarly journals Modeling He-Rich Disks in AM CVn Binaries

2004 ◽  
Vol 194 ◽  
pp. 228-228
Author(s):  
T. Nagel ◽  
S. Dreizler ◽  
T. Rauch ◽  
K. Werner
Keyword(s):  
Accretion Disk ◽  
Time Scales ◽  
Accretion Disks ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
X Ray ◽  
Synthetic Spectra ◽  
Pure Helium ◽  
Low Mass ◽  
X Ray Binaries

We have developed a new code for the calculation of synthetic spectra and vertical structures of accretion disks in cataclysmic variables and compact X-ray binaries. Here we present results for the CV system AM CVn.AM CVn stars are a special type of cataclysmic variables, also called helium cataclysmics. They are systems of interacting binary white dwarfs, consisting of a degenerate C-O white dwarf primary and a low mass semi-degenerate secondary. The secondary loses mass, almost, pure helium, to the primary, forming an accretion disk. They have all in common a helium-rich composition, analoguous to the hydrogen-rich cataclysmic variables. They show photometric variabilities on time scales of ~ 1000s, the prototype of the class, AM CVn, e.g. exhibits a variability of ~ 18 min (Nelemans et al. 2001).

scholarly journals Quasi-simultaneous radio and X-ray observations of Aql X-1 : probing low luminosities

2019 ◽  
Vol 492 (2) ◽  
pp. 2858-2871 ◽  
Author(s):  
N V Gusinskaia ◽  
J W T Hessels ◽  
N Degenaar ◽  
A T Deller ◽  
J C A Miller-Jones ◽  
...  
Keyword(s):  
Neutron Star ◽  
Large Array ◽  
Very Large Array ◽  
X Ray ◽  
Upper Limits ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Low X ◽  
Power Law Index ◽  
X Ray Binaries

ABSTRACT Aql X-1 is one of the best-studied neutron star low-mass X-ray binaries. It was previously targeted using quasi-simultaneous radio and X-ray observations during at least seven different accretion outbursts. Such observations allow us to probe the interplay between accretion inflow (X-ray) and jet outflow (radio). Thus far, these combined observations have only covered one order of magnitude in radio and X-ray luminosity range; this means that any potential radio–X-ray luminosity correlation, LR ∝ LXβ, is not well constrained (β ≈ 0.4–0.9, based on various studies) or understood. Here we present quasi-simultaneous Very Large Array and Swift-XRT observations of Aql X-1’s 2016 outburst, with which we probe one order of magnitude fainter in radio and X-ray luminosity compared to previous studies (6 × 1034 erg s−1 &lt; LX &lt;3 × 1035 erg s−1, i.e. the intermediate to low-luminosity regime between outburst peak and quiescence). The resulting radio non-detections indicate that Aql X-1’s radio emission decays more rapidly at low X-ray luminosities than previously assumed – at least during the 2016 outburst. Assuming similar behaviour between outbursts, and combining all available data in the hard X-ray state, this can be modelled as a steep β =$1.17^{+0.30}_{-0.21}$ power-law index or as a sharp radio cut-off at LX ≲ 5 × 1035 erg s−1 (given our deep radio upper limits at X-ray luminosities below this value). We discuss these results in the context of other similar studies.

scholarly journals The Uses of a VLT for Complementing Observations with Radio and Space Telescopes

1984 ◽  
Vol 79 ◽  
pp. 723-724
Author(s):  
Donald N.B. Hall
Keyword(s):  
Electromagnetic Spectrum ◽  
Large Array ◽  
Space Telescopes ◽  
Very Large Array ◽  
X Ray ◽  
International Ultraviolet Explorer ◽  
Infrared Astronomical Satellite ◽  
Astronomical Satellite

It is now evident that major advances in observational sensitivity in other regions of the electromagnetic spectrum invariably lead to heavy demand for complementary observations with existing large (3- to 5-meter) optical/infrared (O/IR) telescopes, and that such observations are often essential to the interpretation and understanding of phenomena revealed by the former. The Einstein X-ray mission, the International Ultraviolet Explorer (IUE), the Very Large Array (VLA) and the recent Infrared Astronomical Satellite (IRAS) are all clear demonstrations of this effect.

scholarly journals Formation time-scales for high-mass X-ray binaries in M33

2018 ◽  
Vol 479 (3) ◽  
pp. 3526-3544 ◽  
Author(s):  
Kristen Garofali ◽  
Benjamin F Williams ◽  
Tristan Hillis ◽  
Karoline M Gilbert ◽  
Andrew E Dolphin ◽  
...  
Keyword(s):  
Time Scales ◽  
Formation Time ◽  
High Mass ◽  
X Ray ◽  
X Ray Binaries

scholarly journals A New PG 1159-Type Central Star Discovered in the ROSAT XRT All Sky Survey: Non-LTE Analysis of X-Ray and Optical Spectra

1993 ◽  
Vol 155 ◽  
pp. 496-496
Author(s):  
K. Werner ◽  
C. Motch ◽  
M. Pakull
Keyword(s):  
Surface Brightness ◽  
Central Star ◽  
Model Atmosphere ◽  
Complete Agreement ◽  
Atmospheric Parameters ◽  
Low Gravity ◽  
X Ray ◽  
Sky Survey ◽  
Optical Wavelengths

We report on the discovery of a new PG 1159 star in the ROSAT XRT all sky survey and give results of a model atmosphere analysis. The X-ray source RX J2117.1+3412 is relatively faint (0.33 cnts−1) and extremely soft. Ground based optical follow-up spectroscopy (OHP, France) proofs its PG 1159 nature: It belongs to the “low gravity emission” spectral subtype. Optically, it is the second brightest PG1159 star. CCD [O III] imagery reveals that the star is surrounded by an old arc-shaped planetary nebula of faint surface brightness. The spectral analysis of the central star was performed with non-LTE line blanketed model atmospheres (Werner 1992). We find a complete agreement between the atmospheric parameters determined at optical wavelengths and in the ROSAT PSPC energy range.

scholarly journals Variable radio AGN at high redshift identified in the VLA Sky Survey

2020 ◽  
Vol 15 (S359) ◽  
pp. 27-32
Author(s):  
Kristina Nyland ◽  
Dillon Dong ◽  
Pallavi Patil ◽  
Mark Lacy ◽  
Amy Kimball ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Very Large Array ◽  
The Past ◽  
Sky Survey ◽  
Upper Limits ◽  
Radio Transients ◽  
Variable Radio

AbstractAs part of an on-going study of radio transients in Epoch 1 (2017–2019) of the Very Large Array Sky Survey (VLASS), we have discovered a sample of 0.2 < z < 3.2 active galactic nuclei (AGN) selected in the optical/infrared that have recently brightened dramatically in the radio. These sources would have previously been classified as radio-quiet based on upper limits from the Faint Images of the Radio Sky at Twenty-centimeters (FIRST; 1993-2011) survey; however, they are now consistent with radio-loud quasars. We present a quasi-simultaneous, multi-band (1–18 GHz) VLA follow-up campaign of our sample of AGN with extreme radio variability. We conclude that the radio properties are most consistent with AGN that have recently launched jets within the past few decades, potentially making them among the youngest radio AGN known.

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