ALMA Observations of PSR B1259-63/LS 2883 in an Inactive Period: Variable Circumstellar Disk?. (arXiv:2005.00017v3 [astro-ph.HE] UPDATED)

ALMA Observations of PSR B1259-63/LS 2883 in an Inactive Period: Variable Circumstellar Disk?. (arXiv:2005.00017v3 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Fujita_Y/0/1/0/all/0/1">Yutaka Fujita</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Akahori_H/0/1/0/all/0/1">Hiroshi Nagai. Takuya Akahori</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawachi_A/0/1/0/all/0/1">Akiko Kawachi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Okazaki_A/0/1/0/all/0/1">Atsuo T. Okazaki</a>

We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the gamma-ray binary system containing the pulsar PSR B1259-63 orbiting around
a massive star LS 2883 in an inactive period between the 2017 and 2021
periastron passages. We detected radio continuum emission from the binary
system at 97 GHz (Band 3) and 343 GHz (Band 7). Compared with our previous ALMA
observations performed soon after the 2017 periastron passage, the fluxes have
decreased by an factor of six at 97 GHz and two at 343 GHz. The flux at 343 GHz
is large relative to that at 97 GHz and appears to be thermal emission from the
circumstellar disk around LS 2883. The decrease of the 343 GHz flux may
indicate that the disk has expanded and become partially optically-thin since
the disk is no longer affected by pulsar winds. The flux at 97 GHz is
consistent with that expected from the pulsed emission from the pulsar, which
indicates that the unpulsed emission that had been produced through pulsar-disk
or pulsar-stellar wind interaction has disappeared. The image of the system is
consistent with a point source and shows no sign of ejecta.

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