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ATEL #10142

Title: A New Active Stage of the Symbiotic Star CH Cygni

Author: Takashi Iijima (INAF Astronomical Observatory of Padova, AsiagoStation)
Posted: 4 Mar 2017; 04:22 UT
Subjects:Optical, Cataclysmic Variable, Star, Variables

The spectral variation of the symbiotic star CH Cygni has been monitored at Asiago Astrophysical Observatory using the 1.22m Galileo telescope.
Recently, P Cygni type high velocity absorption components appeared on the H I Balmer lines, which were not seen in early December 2016. The blue-shifts of the absorption components from the narrow emission ones were -1890 km/s on 2017 Jan. 24.20 UT, -2040 km/s on Feb. 15.19, -2240 km/s on Feb. 26.13,
and -1930 km/s on March 3.16. The equivalent widths of those of H_beta on respective date were 0.16, 0.17, 0.32, and 0.09 nm, and their FWHMs were roughly 0.6 nm. This object has probably entered a new active stage.

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 star.

"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

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

It’s all about the  standstills, those episodes where the star gets stuck at a mid-point between maximum and minimum. If it doesn’t exhibit standstills it isn’t a Z Cam star.

AM Her stars in need of further investigation

Data from Catalina Real Time Survey 
Drake et al. 2009, ApJ, 696, 87

Northern CVs brighter than 17th magnitude here.

Southern CV's brighter than 17th magnitude here.


New outbursts and unusual activity reported in the last 72 hours

Last updated 08:46 UT March 29, 2017


V1040 Cen
KV Dra
CT Hya
CN Ori
BX Pup
RX Vol
NSV 5031

AG Aps
AH Her
IU Leo
NSV 14581

SDSS J091001.63+164820.0

# indicates a noteworthy or unusual outburst
:  indicates confirmation required
'Activity At A Glance' is gleaned from observations reported to AAVSO MyNewsFlash, BAAVSS-Alert, CVnet-Outburst, VSObs-share and VSNET-outburst. We sincerely thank all the observers who contribute timely observations and reports of activity to these email lists.


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