Bibcode
Tetarenko, A. J.; Bahramian, A.; Sivakoff, G. R.; Tremou, E.; Linares, M.; Tudor, V.; Miller-Jones, J. C. A.; Heinke, C. O.; Chomiuk, L.; Strader, J.; Altamirano, D.; Degenaar, N.; Maccarone, T.; Patruno, A.; Sanna, A.; Wijnands, R.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 460, Issue 1, p.345-355
Fecha de publicación:
7
2016
Número de citas
32
Número de citas referidas
30
Descripción
We present the results of Very Large Array, Australia Telescope Compact
Array, and Swift X-ray Telescope observations of the 2015 outburst of
the transient neutron star X-ray binary (NSXB), EXO 1745-248, located in
the globular cluster Terzan 5. Combining (near-) simultaneous radio and
X-ray measurements, we measure a correlation between the radio and X-ray
luminosities of L_R∝ L_X^β with β =1.68^{+0.10}_{-0.09},
linking the accretion flow (probed by X-ray luminosity) and the compact
jet (probed by radio luminosity). While such a relationship has been
studied in multiple black hole X-ray binaries (BHXBs), this work marks
only the third NSXB with such a measurement. Constraints on this
relationship in NSXBs are strongly needed, as comparing this correlation
between different classes of XB systems is key in understanding the
properties that affect the jet production process in accreting objects.
Our best-fitting disc-jet coupling index for EXO 1745-248 is consistent
with the measured correlation in NSXB 4U 1728-34 (β = 1.5 ±
0.2) but inconsistent with the correlation we fit using the most recent
measurements from the literature of NSXB Aql X-1 (β
=0.76^{+0.14}_{-0.15}). While a similar disc-jet coupling index appears
to hold across multiple BHXBs in the hard accretion state, this does not
appear to be the case with the three NSXBs measured so far.
Additionally, the normalization of the EXO 1745-248 correlation is lower
than the other two NSXBs, making it one of the most radio faint XBs ever
detected in the hard state. We also report the detection of a type-I
X-ray burst during this outburst, where the decay time-scale is
consistent with hydrogen burning.