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Alert Notice 677: Recurrent nova V3890 Sgr in outburst

August 28, 2019

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
  -   Campaigns and Observing Reports: https://www.aavso.org/v3890-sgr-outburst-2019
  -   Novae: https://www.aavso.org/v3890-sagittarii-now-third-recorded-eruption-67-mag
  -   Spectroscopy: https://www.aavso.org/node/66176
  -   Time Sensitive Alerts: https://www.aavso.org/v3890-sagittarii-now-third-recorded-eruption-67-mag-0

The symbiotic star and recurrent nova V3890 Sgr is in outburst, its third recorded outburst. The current outburst was first reported by Alfredo Pereira (Carnaxide, Portugal, reported via vsnet-alert 23505), who observed it on 2019 August 27.870 UT at visual magnitude 6.7. Previous outbursts occurred in 1962 and 1990.

Dr. Ulisse Munari (University of Padua, Asiago Observatory) requests photometry and spectroscopy beginning immediately. He writes: "(U)BVRI filter photometry with a cadence of 1 observation every hour for each individual observer would be great. It is vital to start the observations as soon as possible because we expect a very rapid evolution, at least for the first two weeks, and a return to quiescence brightness in less than two months.

"In these first hours/days the brightness of the system is dominated by recombination within the wind of the cool giant suddenly ionized by the initial UV flash from the outbursting companion. In a few days, the wind will have recombined to neutral conditions and be replaced in keeping the nova bright by the expanding ejecta. The ejecta are fast moving and smashing against the quit wind from the giant, causing a hell of a collision and all the associated high energy phenomena (X- and gamma-rays included).

"Time-series observations are not requested, the orbital period being longer than a year. Unfiltered photometry will be of no/very modest use."

J. Strader et al. (ATel #13047) report that spectroscopic confirmation of a new nova outburst of V3890 Sgr was obtained using the Goodman spectrograph on the SOAR telescope on 2019 Aug. 27.98 UT.

Dr. Munari continues: "I'm also very interested to receive spectra from AAVSO observers. Low resolution and wide wavelength range spectra, as well as higher resolution spectra focusing on emission lines (in particular Halpha), will be great. For those performing flux calibration, I suggest to adopt the bright and nearby standards:

    HR 6698  17 59 01.59 -09 46 25.08   V=3.33
    HR 6700  17 59 47.55 -23 48 58.02   V=4.75

"The most obvious effect we may expect to find in the spectra is the sharpening of emission lines with time, as the result of the nova ejecta being decelerated by the pre-existing wind from the giant. It is important to carefully focus the spectrograph prior to any observation so to avoid being fooled by line broadening caused by out-of-focus instruments."

Dr. Stella Kafka (AAVSO) also requests spectroscopy. In a post to the AAVSO Spectroscopy forum, she writes: "All resolutions are needed! For high-res spectra, please focus on emisison lines (especially H-alpha)...Please submit your spectra to the AAVSO [spectroscopy] database at: https://www.aavso.org/apps/specdb/submit ."

V3890 Sgr is 18.4 V at minimum. Observations reported to the AAVSO include:
2019 Aug. 25.56810 UT, 15.8 (R. Stubbings, Tetoora Road, VIC, Australia);
26.54510, 15.2 (Stubbings);
27.52080, 15.2 (Stubbings);
27.870, 6.7 (A. Pereira, Carnaxide, Portugal, via vsnet-alert 23505);
28.03472, 7.4 (A. Amorim, Florianopolis, Brazil);
28.04868, 7.340 V +/-0.001 (K. Sokolovsky, Moscow, Russian Fed., selected from 1422 observations made Aug. 28);
28.04875, 7.318 V +/-0.001 (Sokolovsky);
28.04969, 7.333 V +/-0.001 (Sokolovsky);
28.05168, 7.994 B +/-0.001 (Sokolovsky);
28.08076, 7.232 V +/-0.001 (Sokolovsky);
28.08083, 7.238 V +/-0.001 (Sokolovsky);
28.10906, 7.184 V +/-0.001 (Sokolovsky);
28.15571, 7.277 V +/-0.001 (Sokolovsky);
28.17800, 7.415 V +/-0.001 (Sokolovsky);
28.382, 8.1 (P. Williams, Heathcote, NSW, Australia);
28.441, 8.03 V +/-0.02 (R. Modic, Willoughby, OH);
28.44940, 8.14 V +/-0.07 (R. Fidrich, Budapest, Hungary);
28.45347, 8.1 (A. Pearce, Nedlands, W. Australia);
28.52847, 8.1 (Pearce);
28.60347, 8.1 (Pearce);

Coordinates: R.A. 18 30 43.28  Dec. -24 01 08.9 (J2000.0)

Charts with comparison stars for V3890 Sgr may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the name V3890 SGR.

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