Bibcode
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 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 Zieliński 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.