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Alert Notice 667: V386 Ser to be observed with HST

Updated May 24, 2019: Dr. Paula Szkody informs us that the exact time for the HST observation of V386 Ser has been scheduled for 2019 May 30 04:36-10:15 UT. This is the night of May 29/30 for US observers. Thus, the critical night will be May 28/29 (Wednesday night)  to get a measurement to HST so they can proceed to the observation. It will be essential to have positive observations from this night to satisfy the HST planners, so observers with suitable equipment are urged to obtain positive measurements of this faint star. Please switch from nightly monitoring to intensive monitoring (several times per night) on May 26/27 and continue through June 1/2, then resume nightly monitoring through June 7/8. Many thanks - Elizabeth O. Waagen, AAVSO HQ

May 20, 2019: Dr. Paula Szkody (University of Washington) has requested AAVSO assistance in monitoring the cataclysmic variable V386 Ser in support of observations scheduled with the Hubble Space Telecope for 2019 May 30 - 2019 June 1 UT.

Nightly snapshots are requested beginning immediately and continuing through June 7. Intensive monitoring is requested May 27 through June 2; this period of intensive monitoring may be adjusted when the exact time of the HST observations is known. When the exact time is known, it will be posted to the AAVSO forum thread on this campaign (see below) and this Alert Notice will be updated online. During the period of intensive observations, prompt submission of observations will be critical.

AAVSO observations are essential to know the state of the V386 Ser system in order to ensure that the system is NOT in outburst when observed with HST. AAVSO observations made 24 hours before the HST observing time will be used to make a go/no-go decision; AAVSO data will be used in the analysis of the resulting HST data.

V386 Ser (UGWZ+ZZ/GWLIB = WZ Sge type with a non-radially pulsating white dwarf) is faint at quiescence (V~19.2). It had an outburst in January 2019, and on 2019 May 18.1018 UT had declined to V=18.407 +-0.012 (B. Harris, New Smyrna Beach, FL). There is a V=17.757 star to the NW of the variable (178 in the AAVSO comparison star sequence; R.A. 16 10 33.15 Dec. -01 02 14.2); knowing whether the variable is fainter than, comparable to, or brighter than it will be very useful.

If visual observers are unable to detect V836 Ser, please report any "fainter-than" estimates using the magnitude of the faintest comparison star magnitude seen. CCD observers are asked to use filters during observations if available; V is preferred. Detection of the variable itself is not required unless you can reach V=18.4 in reasonable time, but please use sufficient exposure to detect at least the 178 comparison star with a S/N of 10 and report the observation as a "fainter-than" observation. V386 Ser may be as bright as V=10.4 in outburst.

Coordinates (J2000): R.A. 16 10 33.63  Dec. -01 02 23.2

Charts with a comparison star sequence for V386 Ser may be created using the AAVSO Variable Star Plotter (VSP).

Please report all observations to the AAVSO International Database using the name V386 SER.

AAVSO Forums: This campaign is the topic of the AAVSO Campaigns and Observation Reports forum thread https://www.aavso.org/v386-ser-campaign-2019 and the Cataclysmic Variables forum thread https://www.aavso.org/v386-ser-campaign-2019-01

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

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