Alert Notice 719: Light curves for symbiotic star ASAS J190559-2109.4

August 26, 2020

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Adrian Lucy (Columbia University) requests AAVSO assistance in obtaining photometry to create light curves "of the newly-discovered symbiotic binary ASAS J190559-2109.4, which shows 5-20% B band flux variations on timescales of minutes to hours in Las Cumbres Observatory observations.

"The primary goal of this call for observations is to test the capability of AAVSO observers' equipment to detect low-to-moderate-amplitude accretion disk flickering in red giant + white dwarf binaries at B~14-15 mag, since that is a flux regime in which our group expects to find more symbiotic candidates in the SkyMapper survey. The results will help inform the interpretation of any apparent variability observed in symbiotic candidates without observations by professional astronomers, guide future coordinated observations for this project, and provide more information on the flickering in this object."

Observing requirements

- B band slightly preferred; V band is still very useful

- SNR~100 per measurement preferred; >= 30 is still useful

- Cadence of 20 minutes or faster (ideally <=5 minutes), for at least
2 or 3 hours, ideally ~5 hours, at airmass <= 2

- Simultaneous observations by geographically-separated observers are encouraged (but not necessary).

The campaign will continue until enough data have been submitted to create light curves that are sufficient for Lucy's needs. The end of the campaign will be announced in the AAVSO forum thread given above; please be sure to subscribe to be kept informed.

Observations in the AAVSO International Database indicate that ASAS J190559-2109.4 was at magnitude 14.663 B +/- 0.01 on 2020 June 29.77762 UT and 13.269 V +/-0.005 on June 29.77925 UT (G. Myers, Hillsborough, CA). ASAS J190559-2109.4 has a V range of 12.4-13.3.

Coordinates (J2000): R.A. 19 05 59.12  Dec. -21 09 25.1  (from VSX entry for ASAS J190559-2109.4)

Charts with comparison stars for ASAS J190559-2109.4 may be created using the AAVSO Variable Star Plotter (VSP).

Please report all observations to the AAVSO International Database using the name ASAS J190559-2109.4.

This AAVSO Alert Notice was prepared by Elizabeth O. Waagen using material supplied by Adrian Lucy.


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