Ultraviolet spectroscopic study of EU UMa and ST LMi from HST and IUE observations |
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| Institution: | 1. Department of Systemics, School of Computer Science, University of Petroleum and Energy Studies, Dehradun, Uttarakhand, India;2. Lovely Professional University, Jalandhar, Punjab, India;1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;2. US Geological Survey, 3215 Marine St., Suite E. 127, Boulder, CO 80303, USA;1. Max-Planck-Institut für Astrophysik (MPA), Karl-Schwarzschild-Strasse 1, Garching 85741, Germany;2. Space Research Institute (IKI), Profsoyuznaya 84/32, Moscow 117997, Russia;3. Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, UPS-OMP, CNRS, 9 Av. colonel Roche, 31028 Toulouse cedex 4, France;4. Moscow Institute of Physics and Technology, Institutsky per. 9, 141700 Dolgoprudny, Russia;5. Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse, Postfach 1312, 85741 Garching, Germany;6. Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr, 92093-0424, La Jolla, USA |
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| Abstract: | We present the first orbit-resolved ultraviolet spectroscopic observations of the two polar systems EU UMa and ST LMi obtained with the Hubble Space Telescope Faint Object Spectrograph (HST FOS) and International Ultraviolet Explorer (IUE) during their intermediate- and low-luminosity states in the period between 1982 and 2003. Different line profiles of the two systems showing variations of line fluxes at different orbital phases are presented. This paper focuses on the C IV emission line at 1550 Å produced in the accretion stream, presenting calculations of spectral line fluxes, ultraviolet luminosities, and accretion rates for the two systems. Our analysis of the spectroscopic data reveals changes with orbital phase of the emission line profiles that correspond to the light curve variations of both EU UMa and ST LMi in the optical and infrared bands. The variations of line fluxes are attributed to variations of both density and temperature as a result of a changing rate of mass transfer from the secondary star to the white dwarf. The ultraviolet luminosity and accretion rate of EU UMa are smaller than the ultraviolet luminosity and accretion rate of ST LMi. |
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| Keywords: | Binary stars Stellar mass loss Stellar magnetic fields Stars: individual (EU UMa ST LMi) |
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