Discovery of a Bow-Shock Nebula around the Z Cam-type Cataclysmic Variable SY Cancri
We report the serendipitous discovery of a bow-shock nebula around the cataclysmic variable (CV) SY Cancri. In addition, SY Cnc lies near the edge of a faint Halpha-emitting nebula with a diameter of about 15'. The orientation of the bow shock is consistent with the direction of SY Cnc's p...
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Main Authors | , , , , , |
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Format | Journal Article |
Language | English |
Published |
10.09.2024
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Subjects | |
Online Access | Get full text |
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Summary: | We report the serendipitous discovery of a bow-shock nebula around the
cataclysmic variable (CV) SY Cancri. In addition, SY Cnc lies near the edge of
a faint Halpha-emitting nebula with a diameter of about 15'. The orientation of
the bow shock is consistent with the direction of SY Cnc's proper motion.
Nebulae are extremely rare around CVs, apart from those known to have undergone
classical-nova (CN) outbursts; bow shocks and off-center nebulae are even more
unusual. Nevertheless, the properties of SY Cnc and its nebulosity are
strikingly similar to those of V341 Ara, another CV that is also associated
with a bow shock and is likewise off-center with respect to its faint Halpha
nebula. Both stars are binaries with optically thick accretion disks, belonging
to the classes of Z Cam CVs or nova-like variables. We discuss three scenarios
to explain the properties of the nebulae. They may have resulted from chance
encounters with interstellar gas clouds, with the stars leaving in their wakes
material that is recombining after being photoionized by UV radiation from the
CVs. Alternatively, the large nebulae could be ejecta from unobserved CN
outbursts in the recent past, which have been decelerated through collisions
with the interstellar medium (ISM), while the stars continue to snowplow
through the gas. Or the faint Halpha nebulae may be ambient ISM that was
shock-ionized by a CN outburst in the past and is now recombining. |
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DOI: | 10.48550/arxiv.2409.06835 |