Details

Autor(en) / Beteiligte

• Russell, T D
• Degenaar, N
• den Eijnden, J van
• Del Santo, M
• Segreto, A
• Altamirano, D
• Beri, A
• Díaz Trigo, M
• Miller-Jones, J C A

Titel

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

Ist Teil von

• Monthly notices of the Royal Astronomical Society. Letters, 2021-11, Vol.508 (1), p.L6-L11

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2021

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• 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 $L_{\rm X (3-10\, keV)} \sim 3.5 \times 10^{37} (D/\rm {7.6\, kpc})^{2}$ 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.