Monitoring 1SWASP J162117.36+441254.2 for HST observations

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Monitoring 1SWASP J162117.36+441254.2 for HST observations

文章 PTS » 週四 16 2月, 2017 09:03

AAVSO Alert Notice 569

February 15, 2017

Monitoring 1SWASP J162117.36+441254.2 for HST observations

Dr. Elme Breedt (University of Warwick) has requested AAVSO
observers' assistance in monitoring the eclipsing cataclysmic
variable 1SWASP J162117.36+441254.2 (= CSS_J162117.4+441254)
beginning now in support of observations scheduled with the Hubble
Space Telescope for late February - early March.

Dr. Breedt writes: "1SWASP J162117.36+441254.2 (=CSS1621+4412) is
an eclipsing binary star with an orbital period of P = 0.207852 d
= 5 h. It was long thought to be a contact binary from the
double-hump profile of its optical light curve and broad primary
and secondary eclipses, but to our surprise, it went into outburst
in June 2016 (Drake et al. 2016 ATEL#9112). Follow-up observations
by AAVSO observers and others revealed that the object was actually
a cataclysmic variable (Scaringi et al. 2016 ATEL#9114; Thorstensen
et al. 2016 ATEL#9141) with a donor star that is unusually hot for
its orbital period.

"We have now been awarded time on the Hubble Space Telescope, with
which we hope to measure the temperature of the white dwarf in this
binary and to look for signs of nuclear evolution of the hot donor

"During outburst, this CV becomes bright enough that it could
damage the HST detectors, so the AAVSO observations will help to
ensure the safety of the instrument. We would like to monitor the
brightness of the target in the run-up to the HST observations to
ensure that the target is not in outburst and that the HST
observations can be executed safely.

"Please monitor 1SWASP J162117.36+441254.2 once per night (V band
or clear fliter) from the middle of February, increasing to twice
per night in the week before the observations. (At the moment the
HST observations are scheduled for sometime between 27 February -
15 March, but an exact date will be assigned and communicated after
16 February). Please report immediately if the target reaches V=14.5
or brighter, as this would indicate that the target is on the rise
to outburst.

"Time series observations during the HST observation window would
be very welcome as well, if possible. Suggested cadence: 2-3 min."

Observers are requested to begin monitoring this star now and
continue until the end of March 2017. Visual observations are also
welcome. 1SWASP J162117.36+441254.2 is V~15.6 at minimum and can be
as bright as V~13.1 at maximum.

An AAVSO Special Notice will be issued once the exact date of the
HST observations is known. Please be sure you have subscribed both
to the Alert Notices and the Special Notices.

Coordinates for 1SWASP J162117.36+441254.2:
R.A. 16 21 17.36 Dec. +44 12 54.1 (2000.0)

Charts: Charts with a comparison star sequence for
1SWASP J162117.36+441254.2 may be created using the AAVSO Variable
Star Plotter (VSP) at

Please submit observations to the AAVSO International Database
using the name 1SWASP J162117.36+441254.2. Report observations as
soon after making them as possible, and immediately if the star is
seen going into outburst.

This campaign is being monitored on the AAVSO Observing Campaigns
webpage at and is being
followed on the Campaigns and Observation Reports Forum at ... g-campaign.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.


Information on submitting observations to the AAVSO may be found at:


An Alert Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL: ... ertnotices



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