Alert Notice 670: KIC 2856960 time series coverage needed now

July 9, 2019

AAVSO Forums: This campaign is the topic of the AAVSO Campaigns and Observation Reports forum thread

Dr. Thomas Marsh (University of Warwick) is requesting times series observations of KIC 2856960 beginning immediately.

Dr. Marsh writes: "I wanted to draw attention to the puzzling triple star KIC 2856960 discovered in Kepler data. A few years back [see AAVSO Alert Notice 525] a group of us tried but failed to understand this system in which a compact 6-hour binary passes in front of a third companion once every 204 days producing a series of dips over a 1.5 day period. It should have been straightforward but it was not.

"[I want] to alert people to the imminent occurrence of the next such passage which I predict to happen over the period 9-11 July, although there are indications from the last such observation in August 2015 that they might start somewhat early [perhaps 8/9 July].

"If you or someone you know can spare some time to carry out time series photometry over the next few days to see whether these events are still occurring and whether they have evolved (quite likely), I would be very grateful. This is the best placed set of events observing-wise since the end of the Kepler mission.

"I have set up a web page with more information:

Quoting from the above web page: "Exposure times from 20 to 600 seconds according to the equipment in use should be fine, but obviously the exposures should be short enough to avoid image trailing and/or saturation, and long enough to avoid too much deadtime between exposures. If possible a colour filter should be used to reduce the effect of colour difference between stars. R is best I think; I or V good alternatives, but filterless ("clear") data are better than none: just the detection of an event is useful. I suggest not cycling through filters. I think intensive observations in a single band are best as they will allow us to build up S-to-N best."

Observations in the AAVSO International Database show KIC 2856960 to be ~ V=15.7-16.1.

Coordinates (J2000): R.A. 19 29 31.52   Dec. +38 04 35.9

Charts with comparison stars for KIC 2856960 may be created using the AAVSO Variable Star Plotter (VSP).

Please report all observations to the AAVSO International Database using the name KIC 2856960.

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


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