| 1. |
- Badelek, B, et al.
(author)
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The photon collider at TESLA
- 2004
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In: International Journal of Modern Physics A. - 0217-751X. ; 19:30, s. 5097-5186
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Research review (peer-reviewed)abstract
- High energy photon colliders (gammagamma,gammae) are based on e(-)e(-) linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.(1) Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.
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| 2. |
- Giele, Walter, et al.
(author)
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The QCD / SM working group: Summary report
- 2002
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In: Physics at TeV colliders. Proceedings, Euro Summer School, Les Houches, France, May 21-June 1, 2001. ; , s. 275-426, s. 275-426
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Conference paper (other academic/artistic)
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| 3. |
- Hackman, T., et al.
(author)
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Doppler images of II Pegasi for 2004-2010
- 2012
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 538, s. A126-
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Journal article (peer-reviewed)abstract
- Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot configuration occurring on a timescale of shorter than a year. The main objective of this study is to determine whether the same phenomena persist in the star during these six years of spectroscopic monitoring. Methods. The observations were collected with the high-resolution SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results. We present 12 new temperature maps that show spots distributed mainly over high and intermediate latitudes. In each image, 1-3 main active regions can be identified. The activity level of the star is clearly lower than during our previous study for the years 1994-2002. In contrast to the previous observations, we detect no clear drift of the active regions with respect to the rotation of the star. Conclusions. Having shown a systematic longitudinal drift of the spot-generating mechanism during 1994-2002, the star has clearly switched to a low-activity state for 2004-2010, during which the spot locations appear more random over phase space. It could be that the star is near to a minimum of its activity cycle.
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| 4. |
- Hackman, T., et al.
(author)
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Spot activity of II Peg
- 2011
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In: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337 .- 1521-3994. ; 332:9-10, s. 859-865
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Journal article (peer-reviewed)abstract
- We have studied the long-term spot activity of the RS CVn star II Peg by means of Doppler imaging based on spectroscopy and time series analysis of photometry. We present 28 Doppler imaging temperature maps spanning the years 1994-2010, of which 14 were calculated for the present study. The longitudinal spot distribution, derived from the surface temperature maps, is compared with epochs of the light curve minima, derived from photometric observations. We detect a longitudinal drift in the major spot structure during 1995-2003. After this there is a clear decrease in the activity level and no clear drift can be seen. We conclude that the variations could be caused by a cyclic behaviour of the underlying magnetic dynamo.
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| 5. |
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| 6. |
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| 7. |
- Kochukhov, O, et al.
(author)
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Magnetic Doppler Imaging of alpha2 CVn
- 2001
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In: Magnetic Fields Across the Hertzsprung-Russell Diagram, Conference Proceedings. ; , s. 321-
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Conference paper (other academic/artistic)
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| 8. |
- Lindborg, M., et al.
(author)
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Doppler images of the RS CVn binary II Pegasi during the years 1994-2002
- 2011
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 526:6, s. A44-
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Journal article (peer-reviewed)abstract
- Aims. We publish 16 Doppler imaging temperature maps for the years 1994-2002 of the active RS CVn star II Peg. The six maps from 1999-2002 are based on previously unpublished observations. Through Doppler imaging we want to study the spot evolution of the star and in particular compare this with previous results showing a cyclic spot behaviour and persistent, active longitudes. Methods. The observations were collected with the SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results. During 1994-2001, our results show a consistent trend in the derived longitudes of the principal and secondary temperature minima over time such that the magnetic structure appears to rotate somewhat more rapidly than the orbital period of this close binary. A sudden phase jump in the active region occurred between the observing seasons of 2001 and 2002. No clear trend over time is detected in the derived latitudes of the spots, indicating that the systematic motion could be related to the drift of the spot-generating mechanism rather than to differential rotation. The derived temperature maps are quite similar to the ones obtained earlier with different methods and the main differences occur in the spot latitudes and relative strength of the spot structures. Conclusions. We observe both longitude and latitude shifts in the spot activity of II Peg. However, our results are not consistent with the periodic behaviour presented in previous studies.
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| 9. |
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| 10. |
- Tautvaisiene, G., et al.
(author)
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Chemical Composition of red horizontal branch stars in the thick disk of the Galaxy
- 2001
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In: Astronomy and Astrophysics. - : EDP Sciences, France. - 0004-6361. ; 380:2, s. 578-589
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Journal article (peer-reviewed)abstract
- High-resolution spectra of 13 core helium-burning stars in the thick disk of the Galaxy have been obtained with the SOFIN spectrograph on the Nordic Optical Telescope to investigate abundances of up to 22 chemical elements. Abundances of carbon were studi
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