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The AAVSO is requesting observations of the symbioticnova candidate ASAS J174600-2321.3 during the predicted upcoming eclipse ofthis system. Observers are asked to begin observing immediately (2015March 5), and continue observations through the end of July 2015. Both visual and instrumental observations areencouraged; the object was at V=12.28 on 2015 February 6.764 (OCN; S. O'Connor, Bermuda). Filtered, transformed photometry in B, V, andIc are especially encouraged, with several observations per night requiredduring the ingress and egress phases. The project is being organized by S. Otero, P. Tisserand,K. Bernhard, and S. Hummerich, and is an extension of the research programdiscussed in Hummerich et al. (2015,eJAAVSO #295, in press).
The researchers have provided the following discussion ofthe project:
"The deeply eclipsing system and likely symbioticnova ASAS J174600-2321.3
RA:17 46 00.18 , Dec: -23 21 16.4 (J2000.0)
is going to enter an eclipse in mid-March according tothe published elements HJD = 2456142 + 1011.5 × E. The eclipse duration isapproximately 115 days.
The system has shown a conspicuous brightening of ~4magnitudes (V) that started in 1999 and has been in outburst since then. Recentphotometry shows the system fluctuating around 12.2 mag (V) as recently as 2014November 07 (JD 2456969.49068; HMB, J. Hambsch, Mol, Belgium, remotely fromChile). It will go fainter than 16.9 mag (V) at mid-eclipse when the red giantpasses in front of the outbursting white dwarf. We might also be seeingsemi-regular pulsations from the red giant during eclipse.
As no observations around mid-eclipse exist after theconsiderable brightening of the primary star, the exact shape of eclipse isopen to conjecture. Thus, no times of second or third contact are given below,although there was a pronounced time of totality during the eclipse that hasbeen covered before the onset of activity in the system (compare Fig. 4, JAAVSO#295).
We encourage visual and CCD observations during theeclipse, preferably multicolour photometry to record the colour changes as thered star starts to dominate the total flux of the system. Observations in V, Band Ic would be very valuable (note, though, that the object will be very faintin B during eclipse). During the ingress and egress phases, severalobservations per night are advisable. During the remainder of the eclipse, oneset of observations per night will be adequate due to the long period of thesystem. Stacking might be advisable to reach the faint magnitudes during theeclipse.
Observations should start as soon as possible to check onthe brightness of the object before the eclipse sets in. Once the event isover, continued photometry with a cadence of one observation per week isencouraged to detect the start of the fading phase of this very slow nova.
Spectroscopic observations near mid-eclipse would be verydesirable, too.
These are the dates observers should keep in mind:
1st contact: 2015 March 14 (JD 2457096) Mid-eclipse: 2015 May 11 (JD 2457153.5) 4th contact: 2015 July 07 (JD 2457211)
The start and end of the eclipse may vary so please bepatient if the eclipse doesn’t start at the predicted date!"
This AAVSO Alert Notice was prepared by S. Hummerich and collaborators,with assistance from M. Templeton.
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發表於 2015-3-6 09:25:06