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The evolving radio jet from the neutron star X-ray binary 4U 1820-30

The evolving radio jet from the neutron star X-ray binary 4U 1820-30
The evolving radio jet from the neutron star X-ray binary 4U 1820-30
The persistently bright ultracompact neutron star low-mass X-ray binary 4U 1820−30 displays an ∼170 d accretion cycle, evolving between phases of high and low X-ray modes, where the 3–10 keV X-ray flux changes by a factor of up to ≈8. The source is generally in a soft X-ray spectral state, but may transition to a harder state in the low X-ray mode. Here, we present new and archival radio observations of 4U 1820−30 during its high and low X-ray modes. For radio observations taken within a low mode, we observed a flat radio spectrum consistent with 4U 1820−30 launching a compact radio jet. However, during the high X-ray modes the compact jet was quenched and the radio spectrum was steep, consistent with optically thin synchrotron emission. The jet emission appeared to transition at an X-ray luminosity of LX(3−10keV)∼3.5×1037(D/7.6kpc)2 erg s−1. We also find that the low-state radio spectrum appeared consistent regardless of X-ray hardness, implying a connection between jet quenching and mass accretion rate in 4U 1820−30, possibly related to the properties of the inner accretion disc or boundary layer.
X-rays: binaries, accretion, accretion discs, radio continuum: transients, stars: neutron
1745-3925
L6-L11
Russell, T.D.
8a000d46-d303-4c7d-82f3-8ccaaa96de5c
Degenaar, Nathalie
347a2379-6b78-482e-976c-52f08a96114d
van den Eijnden, J.
abb08069-7f5c-430a-a68f-6ff0bb0d920a
Del Santo, M.
b192413a-dcb9-4bd4-b3ba-1c689b75cb93
Segreto, A.
250c89f1-8923-4599-8cd6-f320c780c78a
Altamirano, Diego
d5ccdb09-0b71-4303-9538-05b467be075b
Beri, Aru
69ed346a-f02a-4243-83f9-ad5ab4c4008c
Trigo, M. Díaz
4d19116f-45a5-46fe-af82-20f321f4adf0
Miller-Jones, J.C.A.
de372f09-251a-4a6c-93d9-a30ec089473f
Russell, T.D.
8a000d46-d303-4c7d-82f3-8ccaaa96de5c
Degenaar, Nathalie
347a2379-6b78-482e-976c-52f08a96114d
van den Eijnden, J.
abb08069-7f5c-430a-a68f-6ff0bb0d920a
Del Santo, M.
b192413a-dcb9-4bd4-b3ba-1c689b75cb93
Segreto, A.
250c89f1-8923-4599-8cd6-f320c780c78a
Altamirano, Diego
d5ccdb09-0b71-4303-9538-05b467be075b
Beri, Aru
69ed346a-f02a-4243-83f9-ad5ab4c4008c
Trigo, M. Díaz
4d19116f-45a5-46fe-af82-20f321f4adf0
Miller-Jones, J.C.A.
de372f09-251a-4a6c-93d9-a30ec089473f

Russell, T.D., Degenaar, Nathalie, van den Eijnden, J., Del Santo, M., Segreto, A., Altamirano, Diego, Beri, Aru, Trigo, M. Díaz and Miller-Jones, J.C.A. (2021) The evolving radio jet from the neutron star X-ray binary 4U 1820-30. Monthly Notices of the Royal Astronomical Society: Letters, 508 (1), L6-L11. (doi:10.1093/mnrasl/slab087).

Record type: Article

Abstract

The persistently bright ultracompact neutron star low-mass X-ray binary 4U 1820−30 displays an ∼170 d accretion cycle, evolving between phases of high and low X-ray modes, where the 3–10 keV X-ray flux changes by a factor of up to ≈8. The source is generally in a soft X-ray spectral state, but may transition to a harder state in the low X-ray mode. Here, we present new and archival radio observations of 4U 1820−30 during its high and low X-ray modes. For radio observations taken within a low mode, we observed a flat radio spectrum consistent with 4U 1820−30 launching a compact radio jet. However, during the high X-ray modes the compact jet was quenched and the radio spectrum was steep, consistent with optically thin synchrotron emission. The jet emission appeared to transition at an X-ray luminosity of LX(3−10keV)∼3.5×1037(D/7.6kpc)2 erg s−1. We also find that the low-state radio spectrum appeared consistent regardless of X-ray hardness, implying a connection between jet quenching and mass accretion rate in 4U 1820−30, possibly related to the properties of the inner accretion disc or boundary layer.

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4U1820-30_letter_v2 - Accepted Manuscript
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Accepted/In Press date: 22 July 2021
Published date: 30 July 2021
Keywords: X-rays: binaries, accretion, accretion discs, radio continuum: transients, stars: neutron

Identifiers

Local EPrints ID: 452634
URI: http://eprints.soton.ac.uk/id/eprint/452634
ISSN: 1745-3925
PURE UUID: 5e6bbb0e-65da-4613-9451-75d915b5cda0
ORCID for Diego Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

Catalogue record

Date deposited: 11 Dec 2021 11:29
Last modified: 25 Jun 2022 01:46

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Contributors

Author: T.D. Russell
Author: Nathalie Degenaar
Author: J. van den Eijnden
Author: M. Del Santo
Author: A. Segreto
Author: Aru Beri
Author: M. Díaz Trigo
Author: J.C.A. Miller-Jones

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