The $textit{False Widow}$ Link Between Neutron Star X-ray Binaries and Spider Pulsars. (arXiv:2301.13864v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Knight_A/0/1/0/all/0/1">Amy H. Knight</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ingram_A/0/1/0/all/0/1">Adam Ingram</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eijnden_J/0/1/0/all/0/1">Jakob van den Eijnden</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buisson_D/0/1/0/all/0/1">Douglas J. K. Buisson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rhodes_L/0/1/0/all/0/1">Lauren Rhodes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Middleton_M/0/1/0/all/0/1">Matthew Middleton</a>
The discovery of transitional millisecond pulsars (tMSPs) provided conclusive
proof that neutron star (NS) low-mass X-ray binaries (LMXBs) comprise part of
the evolutionary pathway towards binary millisecond pulsars (MSPs). Redback and
black widow `spider’ pulsars are a sub-category of binary MSPs that `devour’
their companions through ablation – the process through which material is
lifted from the stellar surface by a pulsar wind. In addition to reducing the
companion star’s mass, ablation introduces observable characteristics like
extended, energy-dependent and asymmetric eclipse profiles in systems observed
at a sufficiently high inclination. Here, we present a detailed study and
comparison of the X-ray eclipses of two NS LMXBs; $textit{Swift}$
J1858.6$-$0814 and EXO 0748$-$676. Some of the X-ray eclipse characteristics
observed in these two LMXBs are similar to the radio eclipse characteristics of
eclipsing redback and black widow pulsars, suggesting that they may also host
ablated companion stars. X-ray irradiation or a pulsar wind could drive the
ablation. We conduct orbital phase-resolved spectroscopy for both LMXBs to map
the column density, ionization and covering fraction of the material outflow.
From this, we infer the presence of highly ionized and clumpy ablated material
around the companion star in both systems. We term LMXBs undergoing ablation,
$textit{false widows}$, and speculate that they may be the progenitors of
redback pulsars under the assumption that ablation begins in the LMXB stage.
Therefore, the false widows could provide a link between LMXBs and spider
pulsars. The detection of radio pulsations during non-accreting states can
support this hypothesis.
The discovery of transitional millisecond pulsars (tMSPs) provided conclusive
proof that neutron star (NS) low-mass X-ray binaries (LMXBs) comprise part of
the evolutionary pathway towards binary millisecond pulsars (MSPs). Redback and
black widow `spider’ pulsars are a sub-category of binary MSPs that `devour’
their companions through ablation – the process through which material is
lifted from the stellar surface by a pulsar wind. In addition to reducing the
companion star’s mass, ablation introduces observable characteristics like
extended, energy-dependent and asymmetric eclipse profiles in systems observed
at a sufficiently high inclination. Here, we present a detailed study and
comparison of the X-ray eclipses of two NS LMXBs; $textit{Swift}$
J1858.6$-$0814 and EXO 0748$-$676. Some of the X-ray eclipse characteristics
observed in these two LMXBs are similar to the radio eclipse characteristics of
eclipsing redback and black widow pulsars, suggesting that they may also host
ablated companion stars. X-ray irradiation or a pulsar wind could drive the
ablation. We conduct orbital phase-resolved spectroscopy for both LMXBs to map
the column density, ionization and covering fraction of the material outflow.
From this, we infer the presence of highly ionized and clumpy ablated material
around the companion star in both systems. We term LMXBs undergoing ablation,
$textit{false widows}$, and speculate that they may be the progenitors of
redback pulsars under the assumption that ablation begins in the LMXB stage.
Therefore, the false widows could provide a link between LMXBs and spider
pulsars. The detection of radio pulsations during non-accreting states can
support this hypothesis.
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