TY - JOUR
T1 - The path to Z And-type outbursts
T2 - The case of V426 Sagittae (HBHA 1704-05)
AU - Skopal, A.
AU - Shugarov, S. Y.
AU - Munari, U.
AU - Masetti, N.
AU - Marchesini, E.
AU - Komzík, R. M.
AU - Kundra, E.
AU - Shagatova, N.
AU - Tarasova, T. N.
AU - Buil, C.
AU - Boussin, C.
AU - Shenavrin, V. I.
AU - Hambsch, F. J.
AU - Dallaporta, S.
AU - Frigo, A.
AU - Garde, O.
AU - Zubareva, A.
AU - Dubovský, P. A.
AU - Kroll, P.
N1 - Funding Information:
We thank the anonymous referee for constructive comments. Hee-Won Lee is thanked for a discussion on the anomalous flux ratio F(6825)=F(7082) in Sect. 3.3. Matej Sekerás, Theodor Pribulla, Zoltán Garai, Peter Sivani?c and Alisa Shchurova are thanked for their assistance in acquiring some spectra at the Skalnate Pleso and Stará Lesná observatories. Some optical spectra presented in this paper were obtained within the Astronomical Ring for Access to Spectroscopy (ARAS), an initiative promoting cooperation between professional and amateur astronomers in the field of spectroscopy, coordinated by Francois Teyssier. Here, we thank contributions by Paolo Berardi, Stephane Charbonnel, Lorenzo Franco, Tim Lester, Forrest Sims and Umberto Sollecchia. This work was supported by the Slovak Research and Development Agency under the contract No. APVV-15-0458 and by the Slovak Academy of Sciences grant VEGA No. 2/0008/17. This work was partially supported by the Program of Development of M. V. Lomonosov Moscow State University "Leading Scientific Schools", project "Physics of Stars, Relativistic Objects and Galaxies". The spectrograph used at the Astronomical Observatory on the Kolonica Saddle was purchased from the Polish NCN grant 2015/18/A/ST9/00578. NM acknowledges financial support from ASI-INAF contract No. 2017-14-H.0.
Publisher Copyright:
© ESO 2020.
PY - 2020/4/1
Y1 - 2020/4/1
N2 - Context. The star V426 Sge (HBHA 1704-05), originally classified as an emission-line object and a semi-regular variable, brightened at the beginning of August 2018, showing signatures of a symbiotic star outburst. Aims. We aim to confirm the nature of V426 Sge as a classical symbiotic star, determine the photometric ephemeris of the light minima, and suggest the path from its 1968 symbiotic nova outburst to the following 2018 Z And-type outburst. Methods. We re-constructed an historical light curve (LC) of V426 Sge from approximately the year 1900, and used original low- (R ∼ 500-1500; 330-880 nm) and high-resolution (R ∼ 11 000-34 000; 360-760 nm) spectroscopy complemented with Swift-XRT and UVOT, optical UBVRCIC and near-infrared JHKL photometry obtained during the 2018 outburst and the following quiescence. Results. The historical LC reveals no symbiotic-like activity from ∼1900 to 1967. In 1968, V426 Sge experienced a symbiotic nova outburst that ceased around 1990. From approximately 1972, a wave-like orbitally related variation with a period of 493.4 ± 0.7 days developed in the LC. This was interrupted by a Z And-type outburst from the beginning of August 2018 to the middle of February 2019. At the maximum of the 2018 outburst, the burning white dwarf (WD) increased its temperature to ? 2 × 105 K, generated a luminosity of ∼7 × 1037 (d/3.3 kpc)2 erg s-1 and blew a wind at the rate of ∼3 × 10-6 M yr-1. Our spectral energy distribution models from the current quiescent phase reveal that the donor is a normal M4-5 III giant characterised with Teff ∼ 3400 K, RG ∼ 106 (d/3.3 kpc) R and LG ∼ 1350 (d/3.3 kpc)2 L and the accretor is a low-mass ∼0.5 M WD. Conclusions. During the transition from the symbiotic nova outburst to the quiescent phase, a pronounced sinusoidal variation along the orbit develops in the LC of most symbiotic novae. The following eventual outburst is of Z And-type, when the accretion by the WD temporarily exceeds the upper limit of the stable burning. At this point the system becomes a classical symbiotic star.
AB - Context. The star V426 Sge (HBHA 1704-05), originally classified as an emission-line object and a semi-regular variable, brightened at the beginning of August 2018, showing signatures of a symbiotic star outburst. Aims. We aim to confirm the nature of V426 Sge as a classical symbiotic star, determine the photometric ephemeris of the light minima, and suggest the path from its 1968 symbiotic nova outburst to the following 2018 Z And-type outburst. Methods. We re-constructed an historical light curve (LC) of V426 Sge from approximately the year 1900, and used original low- (R ∼ 500-1500; 330-880 nm) and high-resolution (R ∼ 11 000-34 000; 360-760 nm) spectroscopy complemented with Swift-XRT and UVOT, optical UBVRCIC and near-infrared JHKL photometry obtained during the 2018 outburst and the following quiescence. Results. The historical LC reveals no symbiotic-like activity from ∼1900 to 1967. In 1968, V426 Sge experienced a symbiotic nova outburst that ceased around 1990. From approximately 1972, a wave-like orbitally related variation with a period of 493.4 ± 0.7 days developed in the LC. This was interrupted by a Z And-type outburst from the beginning of August 2018 to the middle of February 2019. At the maximum of the 2018 outburst, the burning white dwarf (WD) increased its temperature to ? 2 × 105 K, generated a luminosity of ∼7 × 1037 (d/3.3 kpc)2 erg s-1 and blew a wind at the rate of ∼3 × 10-6 M yr-1. Our spectral energy distribution models from the current quiescent phase reveal that the donor is a normal M4-5 III giant characterised with Teff ∼ 3400 K, RG ∼ 106 (d/3.3 kpc) R and LG ∼ 1350 (d/3.3 kpc)2 L and the accretor is a low-mass ∼0.5 M WD. Conclusions. During the transition from the symbiotic nova outburst to the quiescent phase, a pronounced sinusoidal variation along the orbit develops in the LC of most symbiotic novae. The following eventual outburst is of Z And-type, when the accretion by the WD temporarily exceeds the upper limit of the stable burning. At this point the system becomes a classical symbiotic star.
KW - Binaries: symbiotic
KW - Cataclysmic variables
KW - Novae
KW - Stars: individual: V426 Sagittae (HBHA 1704-05)
UR - http://www.scopus.com/inward/record.url?scp=85084107938&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/201937199
DO - 10.1051/0004-6361/201937199
M3 - Article
AN - SCOPUS:85084107938
VL - 636
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 0004-6361
M1 - 201937199
ER -