Study of Negative and Positive Superhumps in ER Ursae Majoris
Creators: name: Ohshima, Tomohito
name: Kato, Taichi
name: Pavlenko, Elena
name: Akazawa, Hidehiko
name: Imamura, Kazuyoshi
name: Tanabe, Kenji
name: de Miguel, Enrique
name: Stein, William
name: Itoh, Hiroshi
name: Hambsch, Franz-Josef
name: Dubovsky, Pavol A.
name: Kudzej, Igor
name: Krajci, Thomas
name: Baklanov, Alex
name: Samsonov, Denis
name: Antonyuk, Oksana
name: Malanushenko, Viktor
name: Andreev, Maksim
name: Noguchi, Ryo
name: Ogura, Kazuyuki
name: Nomoto, Takashi
name: Ono, Rikako
name: Nakagawa, Shin'ichi
name: Taniuchi, Keisuke
name: Aoki, Tomoya
name: Kawabata, Miho
name: Kimura, Hitoshi
name: Masumoto, Kazunari
name: Kobayashi, Hiroshi
name: Matsumoto, Katsura
name: Shiokawa, Kazuhiko
name: Shugarov, Sergey Yu.
name: Katysheva, Natalia
name: Voloshina, Irina
name: Zemko, Polina
name: Kasai, Kiyoshi
name: Ruiz, Javier
name: Maehara, Hiroyuki
name: Virnina, Natalia
name: Virtanen, Jani
name: Miller, Ian
name: Boitnott, Boyd
name: Littlefield, Colin
name: James, Nick
name: Tordai, Tamas
name: Robaert, Fidrich
name: Padovan, Stefono
name: Miyashita, Atsushi
Publisher: name: arXiv
Year: 2014
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We carried out the photometric observations of the SU UMa-type dwarf nova ER UMa during 2011 and 2012, which showed the existence of persistent negative superhumps even during the superoutburst. We performed two-dimensional period analysis of its light curves by using a method called "least absolute shrinkage and selection operator" (Lasso) and "phase dispersion minimization" (PDM) analysis, and we found that the period of negative superhumps systematically changed between a superoutburst and the next superoutburst. The trend of the period change can beinterpreted as reflecting the change of the disk radius. This change of the disk radius is in good agreement with the predicted change of the disk radius by the thermal-tidal instability (TTI) model. The normal outbursts within a supercycle showed a general trend that the rising rate to maximum becomes slower as the next superoutburst approaches. The change can be interpreted as the consequence of the increased gas-stream flow onto the inner region of the disk as the result of the tilted disk. Some of the superoutbursts were found to be triggered by a precursor normal outburst when the positive superhumps appeared to develop. The positive and negative superhumps co-existed during the superoutburst. The positive superhumps were prominent only during four or five days after the supermaximum, while the signal of the negative superhumps became strong after the middle phase of the superoutburst plateau. A simple combination of the positive and negative superhumps was found to be insufficient in reproducing the complex profile variation. We were able to detect the developing phase of positive superhumps (stage A superhumps) for the first time in ER UMa-type dwarf novae. Using the period of stage A superhumps, we obtained a mass ratio of 0.100(15), which indicates that ER UMa is on the ordinary evolutional track of CVs.
description: PASJ accepted