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AAVSO Alert Notice 580
May 24, 2017: 

ASASSN-17fp, discovered on 2017 April 28 and classified as a helium dwarf nova, was observed to be in outburst again on May 16 after fading 2.5 magnitudes from its original outburst. Dr. Tom Marsh (University of Warwick) and Dr. Elme Breedt (University of Cambridge) requested immediate time-series coverage.

Dr. Breedt wrote: "The transient was identified as a helium dwarf nova (also known as an AMCVn star) from a spectrum taken by the PESSTO survey and reported in ATel #10334. Since then, we have been observing the target using the New Technology Telescope on La Silla in Chile. We measured a photometric period of 51 minutes in the first few nights during which the object was bright at g=16.03 (Marsh et al., ATel #10354), and then it faded to about g~18. However last night [ May 16] it brightened back to g~16 again, apparently starting a second outburst.

"Time series observations during this bright state would be very valuable to determine whether the 51 min period we saw in earlier data returns, and whether it is the orbital period of the binary or related to the distortion of the accretion disc in outburst (superhumps). If the 51 min signal is the orbital period or close to it, this would be the helium dwarf nova with the longest orbital period known. Multiple successive outbursts are not uncommon in binaries like this..."

Dr. Breedt also requested that observers continue to monitor ASASSN-17fp with nightly snapshots for two weeks after it fades, in case it rebrightens again. It appears to have faded, according to an observation in the AAVSO International Database by F.-J. Hambsch (HMB, Mol, Belgium), who observed it remotely from Chile on 2017 May 24.2252 UT at magnitude 19.944 CV +/- 0.595.

Please continue nightly snapshots through June 6 at least, and if it brightens again, resume time series.
     
Coordinates (2000.0): R.A. 18 08 51.11  Dec. -73 04 04.2

Finder charts with a comparison star sequence for ASASSN-17fp may be created using the AAVSO Variable Star Plotter (VSP). To see the sequence, choose an 'e', 'f', or 'g' scale chart.

Observations should be submitted to the AAVSO International Database using the name ASASSN-17fp.

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



ATEL #10142

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

Author: Takashi Iijima (INAF Astronomical Observatory of Padova, AsiagoStation)
Queries: takashi.iijima@oapd.inaf.it
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.




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.



ACTIVITY AT A GLANCE

New outbursts and unusual activity reported in the last 72 hours

Last updated 12:10 UT May 25, 2017

YYYYMMDD

20170525
NSV 14581




# 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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