Low-mass companions to Bright Giants

Niedzielski, A.; Wolszczan, A.; Nowak, G.; Adamów, M.; Deka, B.; Górecka, M.; Kowalik, K.
Referencia bibliográfica

Asymmetrical Planetary Nebulae VI conference, Proceedings of the conference held 4-8 November, 2013. Edited by C. Morisset, G. Delgado-Inglada and S. Torres-Peimbert. Online at http://www.astroscu.unam.mx/apn6/PROCEEDINGS/, id. #63

Fecha de publicación:
4
2014
Número de autores
7
Número de autores del IAC
1
Número de citas
0
Número de citas referidas
0
Descripción
Asymmetric Planetary Nebulae (APN) are formed by bipolar outflows through various mechanism like fast rotation (Blackman et al. 2001), magnetic field (Regos & Tout 1995) or binarity (Harpaz & Soker 1994; Soker 1996; Livio & Soker 2002). The binary scenario seems currently to be best supported by observations as the most efficient in producing the observed APN (De Marco et al. 2004; Soker 2006). Detailed studies of disk formation in binaries leading to APN were presented for instance in Reyes-Ruiz & Lopez (1999), Blackman et al. (2001) and Nordhaus & Blackman (2006). To estimate relative efficiently of the various channels of APN production properties of the population of stars to become AGB stars have to be known. Here our RV search for planets around evolved stars the Penn State-Torun Centre for Astronomy Planet Search (PTPS), whose primary, long-term goal is to improve our understanding of the evolution of planetary systems around aging stars (Niedzielski et al. 2007; Niedzielski & Wolszczan 2008) may be of some help. 1036 stars are monitored within PTPS with the Hobby-Eberly Telescope (HET, Ramsey et al. 1998) and its High Resolution Spectrograph (HRS, Tull et al. 1998) for RV variations using the high precision iodine-cell technique since 2004. The sample is mainly composed of evolved low- and intermediate- mass single or SB1 stars: 449 giants (including 343 clump giants) and 297 subgiants but it also contains 151 slightly evolved dwarfs. All SB1 and SB2 stellar-mass binaries have been identified in the sample. Detailed spectroscopic analysis of 348 stars, mostly giants has been completed by Zieli≈Ñski et al. (2012). Similar analyses for 403 giants and subgiants (Niedzielski et. al. in prep.) and 146 dwarf (Deka et al. in prep.) are in preparation. In addition to stellar atmospheric parameters the spectroscopic studies deliver masses and luminosities (through fits to evolutionary tracks) as well as ages required for further considerations on planetary systems evolution - the main goal of PTPS. The sample was optimized for HET and HRS. It contains relatively bright stars with V in the range of 9-12 mag, randomly distributed over the northern hemisphere. After 2-3 epochs or precise RV HET observations all stars with amplitudes exceeding the HET/HRS PSF FWHM - 5 km s-1 (SB1) or below 5?ERV - ˜ 20-50 m s (single) were rejected from further monitoring. Stars with significant cross-correlation profile variations were identified as SB2 and also excluded. All remaining 300 stars are systematically monitored in search for low-mass companions. Over a dozen stars with planetary-mass companions have already been discovered (Niedzielski et al. 2007, 2009a, b; Gettel et al. 2012a, b; Nowak et al. 2013). Here I will present our new results concerning the most luminous giants with log(L/LSun)> 2, presumably post Horizontal Branch stars.