(cba:news) AAVSO Alert Notice 580: ASASSN-17fp rebrightening event and ongoing monitoring

Joe Patterson jop at astro.columbia.edu
Thu May 25 05:37:41 EDT 2017 

Just saw this one.  Indeed as important as Tom and Elme say, and right 
up our alley too.  While we have been observing it all along at a decent 
clip, it's time to pick up the pace.  For southern observers, this is 
the star-of-the-moment; but I hope northerners can start up on HP Lib.

joe


-------- Forwarded Message --------
Subject: 	[baavss-alert] Fwd: AAVSO Alert Notice 580: ASASSN-17fp 
rebrightening event and ongoing monitoring
Date: 	Thu, 25 May 2017 10:20:09 +0100
From: 	Gary Poyner garypoyner at gmail.com [baavss-alert] 
<baavss-alert at yahoogroups.com>
Reply-To: 	baavss-alert at yahoogroups.com
To: 	Baavss Alert <baavss-alert at yahoogroups.com>




__


   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/ 
<http://aavso.us10.list-manage.com/track/click?u=3ad9dedd265a0351968ebddee&id=8879d732c7&e=d20f381cbb>), 
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) 
<http://aavso.us10.list-manage1.com/track/click?u=3ad9dedd265a0351968ebddee&id=5b2ede628a&e=d20f381cbb>. 
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.

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