51 research outputs found
New and revised parameters for several southern OB binaries
Using ESO FEROS archive spectra of several southern OB-type binaries, we
derived periods for three SB2 spectroscopic binaries, HD 97166, HD 115455, and
HD 123590, and two SB1 systems, HD 130298 and HD 163892. It was also possible
to use new FEROS spectra to improve the parameters of the known binaries, KX
Vel and HD 167263. For KX Vel, we determined a dynamic mass of the primary of
16.8 M, while the evolutionary model suggests a higher value of 20.2
M. We derived an improved period for HD 167263, and in its spectra,
we recognized contributions of both of its interferometric components.Comment: 9 pages, A&A accepte
The Potential of the Timing Method to Detect Evolved Planetary Systems
The timing method, using either stellar pulsations or eclipse timing of close
binaries as a clock, is proving to be an efficient way to detect planets around
stars that have evolved beyond the red giant branch. In this article we present
a short review of the recent discoveries and we investigate the potential of
the timing method using data both from ground-based facilities as well as from
the Kepler and CoRoT space missions.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.6606v1, Proc. of the workshop on "Planetary
Systems beyond the Main Sequence" (Bamberg, 11-14 August 2010), AIPC in press
(eds. S. Schuh, H. Drechsel and U. Heber), 15 pages, 5 figure
News From The Gamma Cephei Planetary System
The Gamma Cephei planetary system is one of the most interesting systems due
to several reasons: 1.) it is the first planet candidate detected by precise
radial velocity (RV) measurements that was discussed in the literature
(Campbell et al. 1988); 2.) it is a tight binary system with a ~ 20AU; and 3.)
the planet host star is an evolved K-type star. In Hatzes et al. (2003) we
confirmed the presence of the planetary companion with a minimum mass of 1.7
M_Jup at 2 AU. In this paper we present additional eight years of precise RV
data from the Harlan J. Smith 2.7 m Telescope and its Tull Coude spectrograph
at McDonald Observatory. The 900 d signal, that is interpreted as the presence
of the giant planetary companion, is strongly confirmed by adding the new data.
We present an updated orbital solution for the planet, which shows that the
planet is slightly more massive and the orbit more circular than previous
results have suggested. An intensive high-cadence week of RV observations in
2007 revealed that Gamma Cep A is a multi-periodic pulsator. We discuss this
issue within the context of searching for additional planets in this system.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.660
Spectral Analysis of Mid-IR Excesses of White Dwarfs
In our Spitzer 24 \mu m survey of hot white dwarfs (WDs) and archival Spitzer
study of pre-WDs, i.e., central stars of planetary nebulae (CSPNs), we found
mid-IR excesses for -15 WDs/pre-WDs. These mid-IR excesses are indicative of
the presence of circumstellar dust that could be produced by sub-planetary
objects. To further assess the nature of these IR-excesses, we have obtained
Spitzer IRS, Gemini NIRI and Michelle, and KPNO 4m echelle spectra of these
objects. In this paper we present the analysis of these spectroscopic
observations and discuss the nature of these IR excesses.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.660
Planets around Extreme Horizontal Branch Stars
We review three main results of our recent study:
We show that a proper treatment of the tidal interaction prior to the onset
of the common envelope (CE) leads to an enhance mass loss. This might increase
the survivability of planets and brown dwarfs that enter a CE phase.
From the distribution of planets around main sequence stars, we conclude that
around many sdB/sdO stars more than one planet might be present. One of these
might have a close orbit and the others at about orbital periods of years or
more.
We show that the intense ionizing flux of the extreme horizontal branch star
might evaporate large quantities of a very close surviving substellar object.
Balmer emission lines from the evaporated gas can be detected via their Doppler
shifts.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.660
Analysis of Two Eclipsing Hot Subdwarf Binaries with a Low Mass Stellar and a Brown Dwarf Companion
The formation of hot subdwarf stars (sdBs), which are core helium-burning
stars located on the extended horizontal branch, is still not understood. Many
of the known hot subdwarf stars reside in close binary systems with short
orbital periods between a few hours and a few days with either M star or white
dwarf companions. Common envelope ejection is the most probable formation
channel. Among these, eclipsing systems are of special importance because it is
possible to constrain the parameters of both components tightly by combining
spectroscopic and light curve analyses. We report the discovery of two
eclipsing binaries with a brown dwarf (< 0.07 M*) and a 0.15 M* late main
sequence star companion in close orbits around sdB stars.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.660
Physical properties of seven binary and higher-order multiple OB systems
Analyses of multi-epoch, high-resolution (~ 50000) optical spectra of seven
early-type systems provided various important new insights with respect to
their multiplicity. First determinations of orbital periods were made for HD
92206C (2.022 d), HD 112244 (27.665 d), HD 164438 (10.25 d), HD 123056A (~ 1314
d) and HD 123056B (< 2 d); the orbital period of HD 318015 could be improved
(23.445975 d). Concerning multiplicity, a third component was discovered for HD
92206C by means of He I line profiles. For HD 93146A, which was hitherto
assumed to be SB1, lines of a secondary component could be discerned. HD 123056
turns out to be a multiple system consisting of a high-mass component A (~
O8.5) displaying a broad He II 5411 A feature with variable radial velocity,
and of an inner pair B (~ B0) with double He I lines. The binary HD 164816 was
revisited and some of its system parameters were improved. In particular, we
determined its systemic velocity to be -7 km/s, which coincides with the radial
velocity of the cluster NGC 6530. This fact, together with its distance,
suggests the cluster membership of HD 164816. The OB system HD 318015 (V1082
Sco) belongs to the rare class of eclipsing binaries with a supergiant primary
(B0.5/0.7). Our combined orbital and light-curve analysis suggests that the
secondary resembles an O9.5III star. Our results for a limited sample
corroborate the findings that many O stars are actually massive multiple
systems.Comment: 16 pages, 16 figures, to appear in Astronomy and Astrophysic
Searching for Planets with White Dwarf Pulsations: Spurious Detections
We present 13 years of pulsation timing measurements of the DBV white dwarf
EC 2005-5234. Each of the four O-C diagrams mimic the sinusoidal behavior
typically attributed to a planet + WD system. However, the amplitude and phase
of the O-C variations are inconsistent with each other. We discuss the impact
of this result on timing based WD planet searches.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.660
Towards a New Prescription for the Tidal Capture of Planets, Brown Dwarfs and Stellar Companions
We study the evolution of the orbit of a planetary companion as the primary
star evolves during the red giant branch phase. Our aim is to determine a
prescription for the capture radius and capture timescales for companions in a
wide range of masses, from planet to star, including the effect of a non
constant f parameter. Our initial results reproduce past findings. According to
our study the mass-loss during the red giant branch does not significantly
affect the semi major axis of the planet and for a 1.5 M star the capture
radius is approximately 300 R or 1.4 AU.Comment: Part of PlanetsbeyondMS/2010 proceedings
http://arxiv.org/html/1011.660
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