MN Draconis: a peculiar, active dwarf nova in the period gap⋆
1 Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716, Warszawa Poland
2 Comets and Meteors Workshop, ul. Bartycka 18, 00-716 Warszawa, Poland
3 Centre for Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland
4 Lajatico Astronomical Centre, Loc i Fornelli No. 9, Orciatico Lajatico, Pisa, Italy
5 Mt. Suhora Observatory, Pedagogical University, ul. Podchorążych 2, 30-084 Kraków, Poland
6 Center for Backyard Astrophysics, Antelope Hills Observatory, 980 Antelope Drive West, Bennett, CO 80102, USA
7 Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
8 Institute of Physics, Astrophysics Division, Jan Kochanowski University, Świętokrzyska 15, 25-406 Kielce, Poland
Received: 30 December 2016
Accepted: 19 March 2017
Context. We present results of an extensive world-wide observing campaign of MN Draconis.
Aims. MN Draconis is a poorly known active dwarf nova in the period gap and is one of only two known cases of period-gap SU UMa objects showing negative superhumps. The photometric behaviour of MN Draconis poses a challenge for existing models of the superhump and superoutburst mechanisms. Therefore, a thorough investigation of peculiar systems like MN Draconis is crucial for our understanding of the evolution of close binary stars.
Methods. To measure the fundamental parameters of the system, we collected photometric data in October 2009, June–September 2013, and June–December 2015. We analysed the light curves, O−C diagrams, and power spectra.
Results. During our three observational seasons we detected four superoutburts and several normal outbursts. Based on the two consecutive superoutbursts detected in 2015, the supercycle length was derived as Psc = 74 ± 0.5 days, and it has been increasing with a rate of ˙P = 3.3 × 10-3 during the past twelve years. Based on the positive and negative superhumps, we calculated the period excess ε = 5.6% ± 0.1%, the period deficit ε− = 2.5% ± 0.6%, and as a result, the orbital period Porb = 0.0994(1) days (143.126 ± 0.144 min). We updated the basic light curve parameters of MN Draconis.
Conclusions. MN Draconis is the first discovered SU UMa system in the period gap with an increasing supercycle length.
Key words: binaries (including multiple): close / stars: individual: MN Draconis / novae, cataclysmic variables / stars: dwarf novae
Photometric data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/A72
© ESO, 2017