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The AAVSO requests time-series observations of theeclipsing binary system KIC 02856960 beginning immediately, with intensivecoverage urgently requested during the window of 2015 August 8.0 through August12.0. Observations are requested onbehalf of an international campaign coordinated by Dr. Thomas Marsh (Universityof Warwick) who is attempting to explain the enigmatic behavior of thispossible triple system. CCD observersaround the world are encouraged to participate, since the observing programrequires as complete temporal coverage as can possibly be obtained. Observers in continental Asia and the Pacificare especially encouraged to participate.
The object is located at the following (J2000)coordinates:
RA:19 29 31.52 , Dec: +38 04 35.9
The star has an approximate V magnitude of around 16.0(B-V ~ 0.85). The short-period component of the system has regulareclipses with a period of 0.2585082 days, and an eclipse depth of less than0.015 magnitudes in V. This campaign isfocused on the longer-period eclipses which occur approximately every 204 days,with a depth of about 0.07 magnitudes. The properties of this system have not been successfully modeled, andobservations of this eclipse are strongly desired to provide additionalconstraints for the modeling efforts. This is a challenging campaign due to the small amplitudes involved(less than 0.1 magnitude) and the relative faintness of the target(V=16.0), but our calculations suggest that the required precision should beachievable by many AAVSO observers using CCD cameras and typical telescopes of20cm and larger.
Observers are asked to obtain photometry at the level of1-2 percent (0.01 to 0.02 magnitudes) or better, using net exposuretimes less than 600 seconds (10 minutes) total. For observers with larger apertures, the useof filters is encouraged if the net exposure time per measurement can be keptbelow 600 seconds, with the Ic and V filters preferred in that order. Only onefilter is needed, and observers may take clear or unfiltered data if needed toreach the required S/N in sufficient time. Exposures of 60 seconds are ideal, however, *please note the following*:if you would otherwise combine multiple exposures to create a stacked imagewith the requisite S/N within 600 seconds, the researchers have asked that yousubmit measurements from the individual frames instead. This will give the researchers additionalflexibility in averaging your observations together, even though your S/N permeasure might be lower than ideal.
Marsh and collaborators request as intense coverage aspossible between 2015 August 8.0 (JD 2457242.5) and 2015 August 11.0(2457245.5); the eclipse event is currently predicted to begin around 2015August 9.5 (JD 2457244.0) and to end around 2015 August 10.4(2457244.9), and the researchers would like at least a day's intensive coverageon either side to better determine each observer's out-of-eclipse meanmagnitude. If possible, we strongly encourage additional time-seriesoutside this window, beginning as early as August 1, and continuing to at leastAugust 14 to provide additional information about the background variations andmean light.
Charts for this object are available via AAVSO VSP:
The AAVSO Sequence Team has assigned a subset of Dr.Marsh's suggested near-field comparison stars for this target that provide areasonable match to the variable's (g-r) color. Observers should use these comparisons if at all possible; please clearlyidentify any and all comparisons used in your report.
Observers are asked to promptly process their photometryand submit their observations as normal via the WebObs feature on the AAVSOwebsite; please clearly indicate which comparison(s) were used and the filter(s) used for the observation. Please use the name "KIC 02856960" when submitting observations, including the leading zero("0") in the KIC identifier.
For more information and scientific background on thiscampaign, please refer to the researchers' website at the following URL:
This AAVSO Alert Notice was prepared by M. Templeton.
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ALERT NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION
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Subscribing and Unsubscribing may be done at thefollowing URL: https://www.aavso.org/observation-notification#alertnotices
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發表於 2015-8-1 09:09:02