RAA 2017 Vol. 17 No. 6, 55 (12pp) doi: 10.1088/1674–4527/17/6/55 R c 2017 National Astronomical Observatories, CAS and IOP Publishing Ltd. esearch in Astronomy and http://www.raa-journal.org http://iopscience.iop.org/raa Astrophysics Optical flare events on the RS Canum Venaticorum star UX Arietis Dong-Tao Cao and Sheng-Hong Gu Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, China;
[email protected],
[email protected] Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650216, China University of Chinese Academy of Sciences, Beijing 100049, China Received 2017 January 23; accepted 2017 February 25 Abstract Based on long-term high-resolution spectroscopic observations obtained during five observ- ing runs from 2001 to 2004, we study optical flare events and chromospheric activity variability of the very activeRS CVn star UX Ari. By means of the spectral subtraction technique, several optical chromo- spheric activity indicators (including the He I D3, Na I D1,D2 doublet, Hα and Ca II IRT lines) covered in our echelle spectra were analyzed. Four large optical flare events were detected on UX Ari during our observations, which show prominent He I D3 line emission together with great enhancement in emis- sion of the Hα and Ca II IRT lines and strong filled-in or emission reversal features in the Na I D1,D2 doublet lines. The newly detected flares are much more energetic than previous discoveries, especially for the flare identified during the 2002 December observing run. Optical flare events on UX Ari are more likely to be observed around two quadratures of the system, except for our optical flares detected during the 2004 November observing run.