Discovery of a new outburst of the bipolar jet-emitter, stable H-burning WD in the symbiotic binary Hen 3-1341

ATel #3946; U. Munari, A. Milani, A. Siviero, S. Dallaporta, G. L. Righetti, P. Valisa, A. Frigo, E. Tamajo, P. Ochner (INAF Padova Astronomical Observatory; ANS Collaboration; Dept. of Physics and Astronomy of the University of Padova; Dept. of Physics of the University of Zagreb)
on 1 Mar 2012; 11:36 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)

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When a week ago we resumed the optical monitoring following its emergence from the conjunction with the Sun, we found that the symbiotic star Hen 3-1341 (V2523 Oph) is undergoing a bright outburst, the first one occurring since the last outburst that peaked in brightness in mid 1999. During the preceding quiescence, the object went down to B=14.179, V=13.353, Rc=12.053, Ic=10.861 on 2009 Sept 11.798 UT, and our last measurement before the current outburst reported it at B=13.948, V=13.231, Rc=11.798 and Ic=10.659 on 2011 July 3.909 UT. The object is still on the rise and has not yet reached maximum brightness as suggested by our latest measurements, giving respectively for Feb 23.194, Feb 27.190 and March 1.168 UT the following values: B=12.248, 12.222, 12.199; V=11.640, 11.609, 11.583; Rc=10.942, 10.900, 10.880; and Ic=10.170, 10.147, 10.128. They correspond to a brightening of 2 magnitudes in B band so far. Hen 3-1341 is a noteworthy object because during its last outburst in 1999 we discovered bipolar jets emanating form it (Tomov, Munari, Marrese A&A 354, L25; Munari et al. 2005, MNRAS 360, 1257), one of the few symbiotic stars known to show them. In 1999 we found that the bipolar jets appeared at outburst maximum and declined in intensity with outburst decline. The strength of the bipolar jets paralleled the intensity of the wind blowing from the outbursting WD. The temperature and luminosity of the WD, as derived from photoionization analysis, strongly suggested that it was in stable H-burning conditions during quiescence. Thus, the optical "outbursts" could be caused by the burning envelope of the WD to react by expanding to an increase in the mass transfer from the M giant companion, with the temperature of the corresponding black-body cooling from 10(5) to 10(4) K. The rising, current brightness of Hen 3-1341 is still about 1 mag fainter that the peak brightness it reached during the 1999 outburst. The 2012 seasonal visibility has just begun, and this offers the possibility to monitor Hen 3-1341 to study the onset and evolution of the bipolar jets, this time being better prepared about what to look. We secured on Feb 27 a 4000-8600 Ang high resolution Echelle spectrum of Hen 3-1341 with the multi-mode spectrograph attached to the 0.6m telescope at Varese Observatory, and on March 1 a low resolution, absolutely fluxed 3300-7700 Ang spectrum with the 1.22m Asiago telescope of the University of Padova, Dept. of Physics and Astronomy. The outburst spectrum has largely changed in comparison with that in quiescence. All high ionization emission lines (HeII, [NeV], [FeVII], Raman scattering of OVI< etc.) have gone, and a strong blue continuum has completely overwhelmed the TiO absorption bands of the M4 giant companion to the outbursting WD. The only significant emission lines that remain visible are the Balmer lines, neutral helium and weak [OIII]. The Balmer continuum remains in strong emission (responsible for largely negative value of the U-B photometric index). Noteworthy, the strong P-Cyg absorption components visible at maximum brightness during the 1999 outburst have not yet developed, neither have the bipolar jets that were observed on Balmer lines at projected radial velocities of +820 and -820 km/sec. We could expect them to emerge soon, as the star will be approaching maximum brightness during the current outburst.