Alert Notice 470: Symbiotic variable V4018 Sgr in outburst

September 20, 2012:  The symbiotic variable V4018 Sgr is undergoing an outburst, according to observations reported to the AAVSO and confirmed by spectroscopy by Ulisse Munari et al. Prompted by an observation and comment from John Bortle (Stormville, NY) (16 June 2012, visual magnitude 12.2) about a possible outburst, Steven O'Connor (St. George's, Bermuda) obtained an observation (10 August 2012, 11.44V) that confirmed V4018 Sgr was bright. His subsequent BVRI observations in September and visual observations by Bortle and Andrew Pearce (Nedlands, Western Australia) show the system brightening and at V magnitude 11.07 as of 2012 Sep. 17.091 UT.

Ulisse Munari (INAF Astr. Obs. Padua, Italy) and colleagues Paolo Valisa and Sergio Dallaporta (ANS Collaboration), after being informed by the AAVSO of the bright state of V4018 Sgr, carried out spectroscopy. Munari writes: "A low resolution, absolutely fluxed 4000-8650 Ang spectrum of V4018 Sgr was obtained on Sept 13.90 UT with the 0.6m telescope of the Schiaparelli Observatory in Varese (Italy). It shows the spectrum of the M giant overwhelmed by a blue continuum up to 6000 Ang, and all high ionization emission lines typical of quiescence are gone, leaving only hydrogen Balmer and weak HeI lines in emission. The spectrum looks like a template one for a symbiotic star in outburst. CCD photometry was obtained on Sept 13.79 UT and provides V=11.027 ± 0.002, B-V=+0.621 ± 0.003. The B-V color is appreciably bluer and the V magnitude much brighter than typical in quiescence (on average V=13.3, B-V=+1.09; Henden and Munari 2008, Baltic Astronomy 17, 293), and support the idea V4018 Sgr is undergoing an outburst."

According to Munari, the last bright outburst of V4018 Sgr was underway in June 1990. Observations in the AAVSO International Database from Albert Jones (Nelson, New Zealand) beginning in May 1992 show the variable at visual magnitude 11.0, with fluctuations between 10.5 and 11.9 through October 1995. Numerous other observers' data show V4018 Sgr remained brighter than visual magnitude 12.0 through November 1999, and returned to its minimum magnitude ~13.7 in June 2001.

Additional spectroscopic and other information on V4018 Sgr is being submitted to The Astronomer's Telegram (ATel) and is expected to appear in an ATel communication.

BVRI photometry (one set per night) and visual observations of V4018 Sgr are requested throughout the current outburst. Spectroscopy is also encouraged.

Representative historical observations and recent observations submitted to the AAVSO International Database include:
2007 Apr. 24.5597 UT, <13.6, (Alan Plummer, Linden, NSW, Australia);
2007 Sep. 13.4771, 13.3 (Peter Williams, Heathcote, NSW, Australia);
2008 Sep. 27.4632, 13.3 (Williams);
2009 Jul. 2.5021, 13.3 (Williams);
2009 Aug. 17.4896, 13.3 (Williams);
2012 Feb. 23.521, 11.59 V+/-0.02 (Steven O'Connor, St. George's, Bermuda);
Feb. 23.7354, 11.7 PTG unfiltered DLSR green (Robert Kaufman, Bright, Victoria, Australia);
Mar. 4.521, 12.49 B+/-0.05 (O'Connor);
Mar. 4.523, 11.77 V+/-0.03 (O'Connor);
Mar. 13.497, 11.49 V+/-0.10 (O'Connor);
Apr. 18.474, 11.71 V+/-0.06 (O'Connor);
Jun. 16.1, 12.2 (John Bortle, Stormville, NY);
Jun. 18.1, 11.6 (Bortle);
Jun. 24.1000, 11.6 (Bortle);
Jun. 28.2000, 11.7 (Bortle);
Jul. 22.1000, 12.0 (Bortle);
Aug. 10.1810, 11.44 V+/-0.04 (O'Connor);
Sep. 3.1290, 11.69 B+/-0.09 (O'Connor);
Sep. 3.1310, 11.06 V+/-0.05 (O'Connor);
Sep. 12.5771, 11.0 (Andrew Pearce, Nedlands, Western Australia);
Sep. 15.1280, 11.67 B+/-0.07 (O'Connor);
Sep. 15.1300, 11.06 V+/-0.07 (O'Connor);
Sep. 15.1320, 10.50 R+/-0.07 (O'Connor);
Sep. 15.1340, 9.63 I+/-0.01 (O'Connor);
Sep. 15.5715, 11.2 (Pearce);
Sep. 16.5785, 11.0 (Pearce);
Sep. 17.0890, 11.64 B+/-0.06 (O'Connor);
Sep. 17.0910, 11.07 V+/-0.05 (O'Connor);

Coordinates: R.A. 18 25 26.84  Dec. -28 35 57.5 (2000.0)

Charts for V4018 Sgr may be created using the AAVSO Variable Star Plotter (VSP) at Photometrists should use the photometry table provided there.

Please report observations to the AAVSO International Database using the name V4018 SGR.

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

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