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Alert Notice 691: Request for immediate photometric monitoring of the fading star ASASSN-V J060000.76-310027.83

January 8, 2020

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports:
https://www.aavso.org/asassnv-j06000076-31002783-campaign-2020

"M. Kenworthy (Leiden Observatory), Z. Way (Ohio State), K. Stanek (Ohio State), E. Gomez (LCO), J. Hambsch (ROAD), R. Bourne, D. Buckley (SAAO), G. Sacco, T.G. Tan (PEST), T. Boyajian (LSU), E. Mamajek (JPL), J. Rodriguez (CfA, Harvard), D. van Dam (Leiden Observatory), C. Bowers (Perth Observatory), A. Verveer (Meckering Observatory)" request AAVSO observers' assistance in monitoring the variable star ASASSN-V J060000.76-310027.83.

"As reported in The Astronomer's Telegram #13346 (Way et al. 2019), the ASAS-SN telescope network discovered a gradually fading star, ASASSN-V J060000.76-310027.83, which has a quiescent mean magnitude of g~14.2 (V~13.6). The star gradually faded from g~14.2 on UT 2019-10-25.35, to g~15.1 on 2019-12-11.16, and monitoring has shown the star fade by up to 0.3 magnitudes over one night.

"The star is a nearby (d~155pc) K5 dwarf star that shows no infrared excess (ATel #13361; McCollum and Laine), ruling out R Cor Bor and warm dust 'dipper star' explanations. The leading hypothesis is that the occulting object is a dust disk around an unseen secondary companion, about 0.1au in diameter and containing detailed substructure similar to that seen towards J1407, PDS 110, and Boyajian's star.

"Photometry in any broadband filter from B to I band is requested, preferably with a cadence of 4 points per hour whenever the star is visible. Our best estimate is that the eclipse will last another 10 days, but this is very uncertain."

Current observations in the AAVSO International Database show ASASSN-V J060000.76-310027.83 at 13.934 V +/-0.014 on 2020 January 8.3277 UT (J.-F. Hambsch, Mol, Belgium).

Coordinates (2000.0): R.A. 06 00 00.76  Dec. -31 00 27.8

Finder charts with comparison stars for ASASSN-V J060000.76-310027.83 may be created using the AAVSO Variable Star Plotter (VSP).

Please submit all photometry data to the AAVSO International Database via WebObs at the AAVSO site using the name ASASSN-V J060000.76-310027.83.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen from information supplied by Dr. Kenworthy.

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