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Vienna, Austria

Schneider P.C.,Hamburger Sternwarte | Eisloffel J.,Thuringer Landessternwarte Tautenburg | Gudel M.,Turkenschanzstrasse | Gunther H.M.,Harvard - Smithsonian Center for Astrophysics | And 3 more authors.
EPJ Web of Conferences | Year: 2014

Classical T Tauri stars (CTTSs) drive strong outflows with temperatures from about 103 K up to a few 106 K. These outflows regulate the angular momentum balance and are therefore tightly related to the accretion process. However, the outflow driving and heating mechanisms are not well understood. We present new HST data of the "prototypical" jet-driving CTTS DG Tau tracing the low-temperature outflow with fluorescently excited far-UV molecular hydrogen emission and the high-temperature part with C IV emission. We find that the spatial distribution of the low-temperature plasma is V-shaped consistent with molecular disk-wind models. Low-velocity shocks (vshock ~ 30 km s-1) are probably the pumping source for the FUV H2 lines. The hot plasma (T > 105 K) is located close to the jet axis at a distance of 40 AU from the driving source and spatially offset from standard (optical) jet-tracers like [S II] or [O I]. It does not show any hints for proper-motion contrasting typical jet properties. The high-temperature plasma is unlikely caused by a hot stellar wind and we propose that the stationary heating is caused by internal shocks or magnetic reconnection. © 2014 Owned by the authors. Source


Schmid V.S.,Turkenschanzstrasse | Themessl N.,Turkenschanzstrasse | Breger M.,Turkenschanzstrasse | Breger M.,Speedway | And 8 more authors.
Astronomische Nachrichten | Year: 2012

Numerous high-resolution spectra of the δ Scuti star 4 CVn were gathered at McDonald Observatory in Texas, USA. They were prepared for interpretation using standard IRAF routines for a subsequent frequency analysis and mode identification with the software FAMIAS. After the reduction process a clear trend in the first moment of the line profile (radial velocity) remained, indicating the signature of binary motion. This was corrected for by fitting a Keplerian orbit, followed by a detailed analysis of the data in the reference frame of the primary. The results of the frequency analysis are in good agreement with previous photometric studies. This paper presents thirteen pulsation modes that were detected in the data sets for the years 2010 and/or 2011. Future work involves spectroscopic mode identification and subsequent seismic modeling. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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