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Alert Notice 672: Monitoring needed of KIC 8462852 (Tabby's Star)

July 19, 2019

AAVSO Campaigns Forum thread (scroll to the bottom of the thread for latest posts): https://www.aavso.org/campaign-kic-8462852

Dr. T. Boyajian (Louisiana State University) has requested time-series observations of the dipper rotating variable KIC 8462852 (Tabby's Star) beginning immediately and continuing through at least the end of September 2019. These observations are requested in support of monitoring by the Transiting Exoplanet Survey Satellite (TESS) underway from now to mid-September.

Dr. Boyajian writes: "From mid-July to mid-September, the TESS satellite will collect nearly continuous, 2 minute cadence photometry of the star (along with missions of others!). TESS data are downlinked ~monthly, and will be critical for investigating any short term, small scale, variability. The coincident, ground based time series collected though this AAVSO alert are highly complementary and not redundant to the TESS observations in two significant ways if a dip is detected: 1) the multi band observations are needed to help interpret the nature of the transiting material, and 2) the near-real time analysis will enable us to trigger more sensitive observations."

Dr. Boyajian continues that observations are also needed to help test a potential ~2 year periodicity, and high quality, multi-band time series can reveal more about the cause of the dips (if detected).

KIC 8462852 (V=11.88 out of dip) has been the topic of AAVSO Alert Notices 532, 542, and 579. It is subject to random, unexplained fading events (dips), first discovered in data from the Kepler mission, and later confirmed from the ground in 2017.

Continuous photometric monitoring (multiband, preferably BVR, or similar) is requested. Please cadence time-series to obtain SNR>75, and use AAVSO comparison stars.

Particularly when observing dips, Dr. Dennis Conti, AAVSO Exoplanet Section chair, recommends the following procedure: "Start your observation when you can after twilight and continue taking images at an exposure that won't saturate your CCD camera (considering that it will brighten as it rises and dims as it falls from your local meridian). Use whatever filter...[as requested by the investigator] and exposure time that gives the best SNR...Be sure to keep your original calibration and image files."

General information about KIC 8462852 and relevant links may be found at: http://www.wherestheflux.com/. Individual fading events (dips) have lasted for several days each, but show complex structure on very short timescales. The star itself is also rotating, and shows rotational variation at the millimagnitude level with a period of 0.8797 day.

Coordinates for KIC 8462852 (J2000): RA 20 06 15.45, Dec +44 27 24.8

Finder charts with comparison stars for KIC 8462852 may be created using the AAVSO Variable Star Plotter (VSP).

Observations should be submitted to the AAVSO International Database using the name KIC 8462852.

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

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