Variable Radio Emission from X-Ray Sources

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.

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The detection of variable radio emission from the fast rotating magnetic hot B-star HR 7355 and evidence for its X-ray aurorae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stx267 ◽

2017 ◽

Vol 467 (3) ◽

pp. 2820-2833 ◽

Cited By ~ 15

Author(s):

P. Leto ◽

C. Trigilio ◽

L. Oskinova ◽

R. Ignace ◽

C. S. Buemi ◽

...

Keyword(s):

Radio Emission ◽

X Ray ◽

Variable Radio ◽

Fast Rotating

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The variable radio counterpart of Swift J1858.6-0814

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1704 ◽

2020 ◽

Vol 496 (4) ◽

pp. 4127-4140 ◽

Cited By ~ 2

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.

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Evidence for radio and X-ray auroral emissions from the magnetic B-type star ρ Oph A

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa587 ◽

2020 ◽

Vol 493 (4) ◽

pp. 4657-4676 ◽

Cited By ~ 3

Author(s):

P Leto ◽

C Trigilio ◽

F Leone ◽

I Pillitteri ◽

C S Buemi ◽

...

Keyword(s):

Magnetic Field ◽

Radio Emission ◽

Rotation Period ◽

Field Measurements ◽

Magnetic Star ◽

Electromagnetic Spectrum ◽

X Ray ◽

Field Geometry ◽

Auroral Emissions ◽

Radio Measurements

Abstract We present new ATCA multiwavelength radio measurements (range 2.1–21.2 GHz) of the early-type magnetic star ρ Oph A, performed in 2019 March during three different observing sessions. These new ATCA observations evidence a clear rotational modulation of the stellar radio emission and the detection of coherent auroral radio emission from ρ Oph A at 2.1 GHz. We collected high-resolution optical spectra of ρ Oph A acquired by several instruments over a time span of about 10 yr. We also report new magnetic field measurements of ρ Oph A that, together with the radio light curves and the temporal variation of the equivalent width of the He i line (λ = 5015 Å), were used to constrain the rotation period and the stellar magnetic field geometry. The above results have been used to model the stellar radio emission, modelling that allowed us to constrain the physical condition of ρ Oph A’s magnetosphere. Past XMM–Newton measurements showed periodic X-ray pulses from ρ Oph A. We correlate the X-ray light curve with the magnetic field geometry of ρ Oph A. The already published XMM–Newton data have been re-analysed showing that the X-ray spectra of ρ Oph A are compatible with the presence of a non-thermal X-ray component. We discuss a scenario where the emission phenomena occurring at the extremes of the electromagnetic spectrum, radio and X-ray, are directly induced by the same plasma process. We interpret the observed X-ray and radio features of ρ Oph A as having an auroral origin.

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Radio, optical and X-ray emission from pulsars

Symposium - International Astronomical Union ◽

10.1017/s0074180900004307 ◽

1970 ◽

Vol 37 ◽

pp. 196-201

Author(s):

B. Bertotti ◽

A. Cavaliere ◽

F. Pacini

Keyword(s):

Radio Emission ◽

Correlation Length ◽

Crab Nebula ◽

Infrared Emission ◽

Appreciable Amount ◽

Electromagnetic Spectrum ◽

X Ray ◽

The Crab Nebula

We examine the electromagnetic spectrum of the Crab Nebula pulsar NP 0532. The present observations are in rough agreement with the idea that the orbit of the radiating particles involves two different radii of curvature. One of the possible models requires electrons with a typical energy of the order of 100 MeV and a density ≈ 109 cm−3. A correlation length of about 10 cm could then give the coherence of the radio emission. Slow pulsars are unlikely to emit an appreciable amount of optical or X-ray radiation but a weak infrared emission is possible.

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The Radio Pulsar J0205+6449 in the SNR 3C 58

Symposium - International Astronomical Union ◽

10.1017/s0074180900181628 ◽

2004 ◽

Vol 218 ◽

pp. 443-444

Author(s):

V. M. Malofeev ◽

I. F. Malov ◽

O. I. Malov ◽

A. P. Glushak

Keyword(s):

Radio Emission ◽

Radio Astronomy ◽

Radio Pulsar ◽

Dispersion Measure ◽

Crab Pulsar ◽

Radio Telescopes ◽

Astronomy Observatory ◽

X Ray ◽

Radio Astronomy Observatory

Pulsed radio emission has been detected from the X-ray pulsar J0205+6449 in the SNR 3C 58 at 111 and 88 MHz on radio telescopes of the Pushchino Radio Astronomy Observatory. The dispersion measure DM = 141 pc cm−3 has been confirmed. The synchrotron mechanism is proposed for the radio and X-ray emission to explain the lower X-ray and radio luminosities of this pulsar compared to the Crab pulsar.

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The Radio Outburst from GRO J1655-40

Symposium - International Astronomical Union ◽

10.1017/s0074180900055832 ◽

1996 ◽

Vol 165 ◽

pp. 369-373 ◽

Cited By ~ 6

Author(s):

R.W. Hunstead ◽

D. Campbell-Wilson ◽

T. Ye

Keyword(s):

Time Delay ◽

Radio Emission ◽

Transverse Velocity ◽

Radio Spectrum ◽

Radio Emissions ◽

X Ray ◽

Radio Outburst ◽

Main Components ◽

Variable Radio

Strong variable radio emission from the bright transient X-ray source GRO J1655-40 (X-ray Nova Scorpii 1994) has been detected at 843 MHz with the Molonglo Observatory Synthesis Telescope (MOST). As the hard X-ray intensity from the 1994 August outburst declined the radio output increased rapidly, reaching a peak of nearly 8 Jy some 12 days after the first X-ray peak. VLBI images obtained at this time showed two main components separating with an apparent transverse velocity > c. The evolution of the radio spectrum suggests that the time delay between X-ray and radio emissions is due, at least in part, to opacity effects associated with this expansion.

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