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2. Discovery of the closest hot subdwarf binary with white dwarf companion

Author

Geier, S., Marsh, T. R., Dunlap, B. H., Barlow, B. N., Schaffenroth, V., Ziegerer, E., Heber, U., Kupfer, T., Maxted, P. F. L., Miszalski, B., Shporer, A., Telting, J. H., Ostensen, R. H., O Toole, S. J., Boris Gaensicke, and Napiwotzki, R.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We report the discovery of an extremely close, eclipsing binary system. A white dwarf is orbited by a core He-burning compact hot subdwarf star with a period as short as $\simeq0.04987 {\rm d}$ making this system the most compact hot subdwarf binary discovered so far. The subdwarf will start to transfer helium-rich material on short timescales of less than $50 {\rm Myr}$. The ignition of He-burning at the surface may trigger carbon-burning in the core although the WD is less massive than the Chandrasekhar limit ($>0.74\,M_{\rm \odot}$) making this binary a possible progenitor candidate for a supernova type Ia event., 6 pages, 2 figures, to be published in the proceedings of 18th European White Dwarf Workshop, Krakow, Poland, ASP Conf. Ser

Published
2012
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4. Solar-like oscillations in the G2 subgiant β Hydri from dual-site observations

Author

Bedding, T. R., Hans Kjeldsen, Torben Arentoft, Bouchy, F., Jacob Brandbyge, Brewer, B. J., Butler, R. P., Jorgen Christensen-Dalsgaard, Dall, T., Søren Frandsen, Christoffer Karoff, Kiss, L. L., Monteiro, M. J. P. F. G., Pijpers, F. P., Teixeira, T. C., Tinney, C. G., Baldry, I. K., Carrier, F., and Toole, S. J. O.

5. Discovery of a stripped red giant core in a bright eclipsing binary star

Author

Maxted, P. F. L., Anderson, D. R., Burleigh, M. R., Collier-Cameron, A., Heber, U., Gansicke, B. T., Geier, S., Kupfer, T., Marsh, T. R., Gijs Nelemans, O Toole, S. J., Ostensen, R. H., Smalley, B., West, R. G., and Bloemen, S.

Subjects
Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We report the serendipitous discovery from WASP archive photometry of a binary star in which an apparently normal A-type star (J0247-25A) eclipses a smaller, hotter subdwarf star (J0247-25B). The kinematics of J0247-25A show that it is a blue-straggler member of the Galactic thick-disk. We present follow-up photometry and spectroscopy from which we derive approximate values for the mass, radius and luminosity for J0247-25B assuming that J0247-25A has the mass appropriate for a normal thick-disk star. We find that the properties of J0247-25B are well matched by models for a red giant stripped of its outer layers and currently in a shell hydrogen-burning stage. In this scenario, J0247-25B will go on to become a low mass white dwarf (M~0.25 solar masses) composed mostly of helium. J0247-25B can be studied in much greater detail than the handful of pre helium white dwarfs (pre-He-WD) identified to-date. These results have been published by Maxted et al., 2011. We also present a preliminary analysis of more recent observations of J0247-25 with the UVES spectrograph, from which we derive much improved masses for both stars in the binary. We find that both stars are more massive than expected and that J0247-25A rotates sub-synchronously by a factor of about 2. We also present lightcurves for 5 new eclipsing pre-He-WD subsequently identified from the WASP archive photometry, 4 of which have mass estimates for the subdwarf companion based on a pair of radial velocity measurements., Comment: To appear in the Proceedings of the Fifth Meeting on Hot Subdwarf Stars and Related Objects (sdOB5), 25 - 29 July 2011, Stellenbosch, South Africa. ASP Conference Series. 10 pages, 8 figures

10. Non-radial pulsation, rotation and outburst in the Be star ω Orionis from the MuSiCoS 1998 campaign

Author

Neiner, C., Hubert, A. -M, Floquet, M., Jankov, S., Henrichs, H. F., Foing, B., Oliveira, J., Orlando, S., Abbott, J., Baldry, I. K., Tim Bedding, Cami, J., Cao, H., Catala, C., Cheng, K. P., Domiciano Souza Jr, A., Janot-Pacheco, E., Hao, J. X., Kaper, L., Kaufer, A., Leister, N. V., Neff, J. E., O Toole, S. J., Schäfer, D., Smartt, S. J., Stahl, O., Telting, J., Tubbesing, S., and Zorec, J.

11. The MUCHFUSS Project: Searching for the Most Massive Companions to Hot Subdwarf Stars in Close Binaries and Finding the Least Massive Ones

Author

Geier, S., Schaffenroth, V., Hirsch, H., Tillich, A., Heber, U., Classen, L., Kupfer, T., Maxted, P. F. L., Ostensen, R. H., Barlow, B. N., O Toole, S. J., Marsh, T. R., Boris Gaensicke, Cordes, O., and Napiwotzki, R.

Subjects
Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions (massive white dwarfs M>1.0 Msun, neutron stars or stellar mass black holes). The existence of such systems is predicted by binary evolution theory and some candidate systems have been found. We classified about 1400 hot subdwarf stars from the Sloan Digital Sky Survey (SDSS) by colour selection and visual inspection of their spectra. Stars with high velocities have been reobserved and individual SDSS spectra have been analysed. In total 201 radial velocity variable subdwarfs have been discovered and about 140 of them have been selected as good candidates for follow-up time resolved spectroscopy to derive their orbital parameters and photometric follow-up to search for features like eclipses in the light curves. Up to now we found seven close binary sdBs with short orbital periods ranging from 0.21 d to 1.5 d and two eclipsing binaries with companions that are most likely of substellar nature. A new pulsating sdB in a close binary system has been discovered as well., 7 pages, 2 figures, To appear in ASP Conference Series; Proceedings of the fifth meeting on hot subdwarf stars and related objects (sdOB05), 25 - 29 July 2011, Stellenbosch, South Africa

12. Discovery of the Closest Hot Subdwarf Binary with White Dwarf Companion

Author

Geier, S., Marsh, T. R., Dunlap, B. H., Barlow, B. N., Schaffenroth, V., Ziegerer, E., Heber, U., Kupfer, T., Maxted, P. F. L., Miszalski, B., Shporer, A., Telting, J. H., Ostensen, R. H., O Toole, S. J., Boris Gaensicke, Napiwotzki, R., Krzesinski, J., Stachowski, G., Moskalik, P., and Bajan, K.

16. Photometric and spectroscopic monitoring of the sdBV star PG 1605+072: The Multi-Site Spectroscopic Telescope (MSST) project

Author

Heber, U., Dreizler, S., Schuh, S. L., O Toole, S., Jeffery, C. S., Falter, S., Woolf, V., Ahmad, A., Billeres, M., Charpinet, S., Cordes, O. -M, For, B. -Q, Green, E., Hyde, E. A., Jacob, A., Kjeldsen, H., Kleinman, S., Krzesinski, J., Lopes, I., Marinoni, S., Mauch, T., Nitta, A., O Donoghue, D., Østensen, R., Pollacco, D., Pereira, R., Tiago Pereira, Reed, M. D., Silvotti, R., Townsend, R., Vuckovic, M., White, B. A., and Jiang, Xiaojun

20. MUCHFUSS: Status and Highlights

Author

Geier, S., Kupfer, T., Barlow, B. N., Schaffenroth, V., Furst, F., Heuser, C., Ziegerer, E., Heber, U., Marsh, T. R., Maxted, P. F. L., Ostensen, R. H., O Toole, S. J., Gansicke, B. T., and Napiwotzki, R.

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