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Alert Notice 631: Coverage requested for current outburst of AG Dra

April 24, 2018: Drs. Jaroslav Merc and Rudolf Gális (both of the Pavel Jozef Šafárik University (Slovakia)), on behalf of their scientific team, have requested AAVSO assistance in observing the symbiotic variable AG Dra as a follow-up to spectroscopic observations and in order to monitor the system in its current outburst, which began in early April.

In a post to the AAVSO's forum thread on AG Dra (link below) on 2018 April 23, Dr. Merc wrote: "according to photometric as well as spectroscopic observations we can confirm that the new outburst of symbiotic system AG Dra is in onset (The Astronomer’s Telegram #11559). It is the fourth hot outburst of this interesting interacting binary during the present active stage.

"The previous three outbursts of AG Dra occurred in May 2015, April 2016, and May 2017 (ATel #7582, ATel #8975, and ATel #10390). The maximal magnitudes (10.7, 9.9, and 10.7 in B filter) rank all these brightenings to the minor outbursts of the symbiotic binary. Such photometric behavior of the active stage is very unusual. More often, the activity of AG Dra starts with a major outburst, during which the brightness can reach the 8.8 and 8.4 mag in B and V band, respectively. Recent outburst activity resembles the weak activity stage 1963–66 (Hric et al. 2014, MNRAS 443, 1103).

"The smooth brightening of AG Dra was recognised at the beginning of April 2018 (JD 2458211, B = 11.01 +/- 0.03 mag and V = 9.68 +/- 0.02 mag) and the onset of new outburst of this symbiotic binary was photometrically confirmed 11 days later (JD 2458222, B = 10.93 +/- 0.03 mag and V = 9.65 +/- 0.02 mag). After next 9 days, the brightness of AG Dra increased by about 0.42 mag and 0.21 mag in B and V filters, respectively. The brightening has occurred after around 340 days after the previous outburst of AG Dra in May 2017 and is still in progress.

"The new outburst of AG Dra was confirmed also spectroscopically. The increase of the HeII/Hbeta ratio (1.16) as well as equivalent widths of the prominent emission lines (He II 37.21, Hbeta 32.20, Halpha 87.97, He I 1.94, OVI 8.72 Ang) suggest that the outburst is of the hot type (Leedjärv et al. 2016, MNRAS 456, 2558) like the previous three outbursts in the present active stage of symbiotic binary AG Dra."

Daily monitoring of AG Dra (V~7.9-10.3) in UBV(RI) filters is requested beginning at once and continuing until further notice. Visual observations are welcome and are encouraged.

The most recent observations submitted to the AAVSO International Database show AG Dra on 2018 Apr. 24.04097 UT at visual magnitude 9.5 (J. O'Neill, Topsfield, MA) and on Apr. 23.85423, 10.336 B +/-0.017 (O. Nickel, Mainz, Germany); 23.50370, 8.514 R +/-0.012 (G. Stone, Auberry, CA); 23.50296, 10.482 B +/-0.003 (Stone); 23.50221, 9.387 V +/-0.005 (Stone).

For more information on AG Dra and its recent behavior, please see AAVSO Alert Notice 572 from 2017, which asked for coverage in anticipation of an expected minor outburst (which occurred in May 2017 and was well observed by AAVSO observers).

Coordinates for AG Dra:  R.A. 16 01 41.01  Dec. +66 48 10.2   (2000.0)

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

Please submit observations to the AAVSO International Database using the name AG DRA.

This campaign is being followed on the AAVSO Campaigns and Observing Reports online forum at https://www.aavso.org/ag-dra-observing-campaign

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