We are intensively monitoring the current outburst on BF Cyg, both spectroscopically (high and low resolution modes) and photometrically (so far 450 BVRCRIC measurements have been collected). The outburst is photometrically reminiscent of the major event BF Cyg experienced in 1890 when it rose by 4 mag in the blue. In this contribution we present the data and describe the plans to investigate this object

Lutz, J.

Siviero, A.

Tamajo, E.

Wallerstein, G.

English

Repositorium für Naturwissenschaften und Technik  (TIB Hannover)

Baltic Astronomy, vol. 21, 188–192, 2012BF CYG DURING ITS CURRENT OUTBURSTA. Siviero1,2, E. Tamajo3,5, J. Lutz4, G. Wallerstein4 and ANS Collaboration61 Department of Astronomy, University of Padova, Asiago, Italy2 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482Potsdam, Germany3 Department of Physics, University of Zagreb, Croatia4 Astronomy Department, University of Washington, Box 351580, Seattle, WA98195, U.S.A.5 INAF Astronomical Observatory of Padova at Asiago, Italy6 ANS Collaboration, c/o Astronomical Observatory, Asiago, ItalyReceived: 2011 September 2; accepted: 2011 October 10Abstract. We are intensively monitoring the current outburst on BF Cyg,both spectroscopically (high and low resolution modes) and photometrically (sofar 450 BV RCIC measurements have been collected). The outburst is photo-metrically reminiscent of the major event BF Cyg experienced in 1890 when itrose by 4 mag in the blue. In this contribution we present the data and describethe plans to investigate this object.Key words: stars: symbiotic binaries – individual (BF Cyg)1. INTRODUCTIONBF Cyg is a S-type symbiotic star and one of the most studied objects of itsclass. The system consists of a M5 III late-type cool component (Belczyński et al.2000) and a hot luminous white dwarf, revolving with an orbital period of 757.2d (Fekel et al. 2001). The system underwent a major outburst in 1890 (Leibowitz& Formiggini 2006, hereafter LF06), that required almost a century to decline toquiescence, and a second one occurred in 2006, with BF Cyg still at maximumbrightness after 5 years. On top of this remarkable light-curve, different typesof variability and recurrence scales have been observed (Figure 1). BF Cyg hasbeen the subject of many intensive investigations over the years. In particularFekel et al. (2001) obtained a spectroscopic orbit from IR data. Yudin et al.(2005) discovered that the cool component fills its Roche lobe causing the infraredlight-curve being modulated by ellipticity variability. LF06 detected a periodicrecurrence of the enhanced luminosity of 6376 d (which they ascribed to somemagnetic activity driven by a magnetic dynamo taking place on the external layerof the giant component, similar to the ∼ 22 year solar magnetic cycle). In theirtime-series analysis, LF06 found also the presence in the light-curve of a furtherperiod of 798.8 d, that they ascribed to the rotation period of the cool star. Inaddition, Formiggini & Leibowitz (2009) reported the discovery of a ≃ 7 mmagamplitude variation in the B passband that they interpreted as the spin period ofBF Cyg during its current outburst 189Fig. 1. Historical light curve of BF Cyg. Data prior to 2006 are from Jacchia 1941,Skopal et al. 1995 and AAVSO. The vertical dashed lines mark the 6376 d periodic vari-ability found by Leibowitz & Formiggini (2006). Blue open circles are ANS Collaborationdata.the WD. Finally, a complete census of the emission and absorption lines visible inhigh resolution spectra (R∼ 35 000) of BF Cyg obtained at the beginning of thecurrent outburst has been presented by McKeever et al. (2011).2. THE 2006 OUTBURSTIn July 2006, Munari et al. (2006) discovered BF Cyg beginning a majoroutburst, so far evolving as a close replica of the 1890 event, when the star rose by4 mag in a couple of years and remained at maximum brightness an additional ∼ 30years, fully qualifying BF Cyg as a member of the very exclusive club of symbioticnovae, whose outbursts last for decades to centuries. A catalog and discussion ofthe symbiotic novae has been presented by Munari (1997), who lists less than 30known symbiotic novae, half of them still close to maximum brightness after ≥ 50years since their discovery. At the time of the 2006 outburst discovery, BF Cygwas under intensive monitoring by the ANS Collaboration (Munari et al. 2012)because an increase in brightness was predicted in 2007 by LF06 following the∼ 6400 d periodicity. The 2006 outburst was enormously brighter and occurreda whole year earlier than the predicted 2007 maximum (Figure 2), indicating thetwo as unrelated events.3. THE PHOTOMETRIC AND SPECTROSCOPIC OBSERVING CAMPAIGNANS Collaboration has so far collected 450 BV RCIC measurements of theBF Cyg outburst (Figure 2), and a tight spectroscopic monitoring program isunderway with the following telescopes: (i) the 1.82 m telescope operated in Asiagoby INAF – Astronomical Observatory of Padova and equipped with a multi-modeAFOSC spectrograph/imager and a high resolution Echelle spectrograph; (ii) the1.22 m telescope operated in Asiago by the Departement of Astronomy of theUniversity of Padova and equipped with a B&C long-slit spectrograph; and (iii) 0.6190 A. Siviero, E. Tamajo, J. Lutz et al.Fig. 2. The ANS Collaboration photometric observing campaign of BF Cyg. Dashedline marks the date of the 6376 d periodicity. Dotted lines mark the orbital periodicityaccording to the JDmin = 2415065 + 757.3×E given by Pučinskas (1970). The asteriskson the top panel mark the time when the spectra displayed in Figure 3 were obtained.m telescope of the Schiaparelli Observatory in Varese equipped with a multi-modespectrograph providing both low resolution and Echelle high resolution spectra. Asample of the low resolution spectra we have collected is presented in Figure 3 tohighlight the spectral evolution of the current outburst.BF Cyg during its current outburst 191Fig. 3. Spectroscopic monitoring in low resolution of BF Cyg since the onset ofthe outburst. Spectra are continuum normalized and plotted on a logarithm flux scale.Principal emission lines are identified.4. CONCLUSIONThe aim of this poster was to present the large and densely mapped set ofphotometric and spectroscopic data the ANS Collaboration project carried outon BF Cyg during its current outburst. The regularity and frequency of themonitoring make the data perfectly suitable for a detailed study (for the firsttime in such objects) of the outburst evolution in terms of physical conditionsof the outbursting component, like Teff of the expanded photosphere, radius andluminosity, and nebular parameters like electronic temperature and density, radiusand chemical composition of the emission region.ACKNOWLEDGMENTS. We thank the AAVSO for the visual magnitudesincorporated in Figure 1.REFERENCESBelczyński K., Mikolajewska J., Munari U. et al. 2000, A&AS, 146, 407Fekel F. C., Hinkle K. H., Joyce R. R., Skrutskie M. F. 2001, AJ, 121, 2219Formiggini L., Leibowitz E. M. 2009, MNRAS, 396, 1512Jacchia L. 1941, Bull. Harv. Coll. Obs., 915, 17Leibowitz E. M., Formiggini L. 2006, MNRAS, 366, 675192 A. Siviero, E. Tamajo, J. Lutz et al.McKeever J., Lutz J., Wallerstein G., Munari U., Siviero A. 2011, PASP, 123, 1062Munari U. 2007, in Physical Processes in Symbiotic Binaries and Related Systems,ed. J. Miko lajewska, Copernicus Fundation for Polish Astronomy, p. 37Munari U., Siviero A., Moretti S. et al. 2006, CBET, 596, 1Munari U. Bacci S., Baldinelli L. et al. 2012, Baltic Astronomy, 21, 13 (this issue)Osterbrock D. E. 1989, Astrophysics of Gaseous Nebulae and Active Galactic Nu-clei, Univ. Sci. Books, California, 422 pagesPučinskas A. 1970, Bull. Vilnius Obs., No. 27, 24Skopal A., Hric L., Chochol D. et al., 1995, Contr. Obs. Skalnaté Pleso, No. 25,53Yudin B. F., Shenavrin V. I., Kolotilov E. A. et al. 2005, Astr. Reports, 49, 232

BF Cyg during ITS current outburst

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BF Cyg during ITS current outburst

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