Optical, X-ray, and $gamma$-ray observations of the candidate transitional millisecond pulsar 4FGL J0427.8-6704. (arXiv:2003.13718v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kennedy_M/0/1/0/all/0/1">M. R. Kennedy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Breton_R/0/1/0/all/0/1">R. P. Breton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Clark_C/0/1/0/all/0/1">C. J. Clark</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dhillon_V/0/1/0/all/0/1">V. S. Dhillon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kerr_M/0/1/0/all/0/1">M. Kerr</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buckley_D/0/1/0/all/0/1">D. A. H. Buckley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Potter_S/0/1/0/all/0/1">S. B. Potter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_D/0/1/0/all/0/1">D. Mata Sánchez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stringer_J/0/1/0/all/0/1">J. G. Stringer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marsh_T/0/1/0/all/0/1">T. R. Marsh</a>
We present an optical, X-ray, and $gamma$-ray study of 1SXPS
J042749.2-670434, an eclipsing X-ray binary which has an associated
$gamma$-ray counterpart, 4FGL J0427.8-6704. This association has led to the
source being classified as a transitional millisecond pulsar (tMSP) in an
accreting state. We analyse 10.5 years of Fermi LAT data, and detect a
$gamma$-ray eclipse at the same phase as optical and X-ray eclipses at the
>5$sigma$ level, a significant improvement on the 2.8$sigma$level of the
previous detection. The confirmation of this eclipse solidifies the association
between the X-ray source and the $gamma$-ray source, strengthening the tMSP
classification. However, analysis of several optical data sets and an X-ray
observation do not reveal a change in the source’s median brightness over long
timescales or a bi-modality on short timescales. Instead, the light curve is
dominated by flickering which has a correlation time of 2.6 min alongside a
potential quasi-periodic oscillation at $sim$21 min. The mass of the primary
and secondary star are constrained to be $M_1=1.43^{+0.33}_{-0.19}$ M$_{odot}$
and $M_2=0.3^{+0.17}_{-0.12}$ M$_{odot}$ through modelling of the optical
light curve. While this is still consistent with a white dwarf primary, we
favour the transitional millisecond pulsar in a low accretion state
classification due to the significance of the $gamma$-ray eclipse detection.
We present an optical, X-ray, and $gamma$-ray study of 1SXPS
J042749.2-670434, an eclipsing X-ray binary which has an associated
$gamma$-ray counterpart, 4FGL J0427.8-6704. This association has led to the
source being classified as a transitional millisecond pulsar (tMSP) in an
accreting state. We analyse 10.5 years of Fermi LAT data, and detect a
$gamma$-ray eclipse at the same phase as optical and X-ray eclipses at the
>5$sigma$ level, a significant improvement on the 2.8$sigma$level of the
previous detection. The confirmation of this eclipse solidifies the association
between the X-ray source and the $gamma$-ray source, strengthening the tMSP
classification. However, analysis of several optical data sets and an X-ray
observation do not reveal a change in the source’s median brightness over long
timescales or a bi-modality on short timescales. Instead, the light curve is
dominated by flickering which has a correlation time of 2.6 min alongside a
potential quasi-periodic oscillation at $sim$21 min. The mass of the primary
and secondary star are constrained to be $M_1=1.43^{+0.33}_{-0.19}$ M$_{odot}$
and $M_2=0.3^{+0.17}_{-0.12}$ M$_{odot}$ through modelling of the optical
light curve. While this is still consistent with a white dwarf primary, we
favour the transitional millisecond pulsar in a low accretion state
classification due to the significance of the $gamma$-ray eclipse detection.
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