| 1. |
- Hrudkova, M., et al.
(author)
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The discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370
- 2017
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 464:1, s. 1018-1028
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Journal article (peer-reviewed)abstract
- We report on the discovery of a planetary companion candidate with a minimum mass M sin i = 4.6 +/- 1.0 M-Jupiter orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our programme to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coude echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph High Efficiency and Resolution Mercator Echelle Spectrograph of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 +/- 4.5 d) variation with a semi-amplitude K = 133 +/- 25 ms(-1), superimposed on a long-term trend. A low-mass stellar companion with an orbital period of similar to 88 yr in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-amplitude radial velocity variations and only future continued monitoring of this system may answer this uncertainty. From Kepler photometry, we find that HD 175370 is most likely a low-mass red giant branch or asymptotic giant branch star.
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| 2. |
- Paunzen, E., et al.
(author)
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A photometric long-term study of chemically peculiar stars in open clusters
- 2011
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 525, s. A16-
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Journal article (peer-reviewed)abstract
- Context. Photometric variability of chemically peculiar (CP) stars of the upper main sequence is closely connected to their local stellar magnetic field and their rotational period. Long term investigations, as presented here, help us to identify possible stellar cycles (as in the Sun). Furthermore, these data provide a basis for detailed surface mapping techniques. Aims. Photoelectric Stromgren uvby time series for 27 CP stars within the boundaries of open clusters are presented. In addition, Hipparcos photometric data (from 1989 to 1993) are used for our analysis. Our observations cover a time period of about six years (1986 to 1992) with typically fifteen measurements for each objects. These observations help us to determine the rotational periods of these objects. Methods. A standard reduction procedure was applied to the data. When possible, we merged our data sets with already published ones to obtain a more significant result. A detailed time series analysis was performed, involving five different methods to minimize spurious detections. Results. We established, for the first time, variability for fourteen CP stars. For additional two stars, a merging of already published data sets, resulted in more precise periods, whereas for six objects, the published periods could be confirmed. Last, but not least, no significant variations were found for five stars. Apart from six stars, all targets seem to be members of their host open clusters. Conclusions. The present observations fill an important gap in previous photometric long-time studies of CP stars. The presented open cluster members are excellent targets for follow-up observations, employing for example polarimetric, high-resolution spectroscopic, and surface mapping techniques.
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| 3. |
- Söderhjelm, Staffan, et al.
(author)
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Observing binaries with Gaia - the global picture
- 2004
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In: Spectroscopically and Spatially Resolving the Components of the Close Binary Stars, Proceedings of the Workshop held 20-24 October 2003 in Dubrovnik, Croatia. ASP Conference Series. ; 318, s. 413-421
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Conference paper (peer-reviewed)abstract
- ESA's Gaia mission will observe huge numbers of binaries with a largerange of periods. The present contribution presents results from somelarge-scale simulations, based on a simplified population synthesismodel Galaxy consisting mostly of binaries. The results are 'typical'solution-numbers and -types, for stellar samples at different distancesfrom the sun. As in previous studies, there are marked distance-effects,with the solar neighborhood (within a few hundred pc) much morecompletely sampled than more typical (few kpc) Gaia distances.
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