60 research outputs found
Detectability of substellar companions around white dwarfs with Gaia
To date not a single-bona fide planet has been identified orbiting a single
white dwarf. In fact we are ignorant about the final configuration of >95% of
planetary systems. Theoretical models predict a gap in the final distribution
of orbital periods, due to the opposite effects of stellar mass loss (planets
pushed outwards) and tidal interactions (planets pushed inwards) during the RGB
and the AGB stellar expansions. Over its five year primary mission, Gaia is
expected to astrometrically detect the first (few tens of) WD massive
planets/BDs giving first evidence that WD planets exist, at least those in wide
orbits. In this article we present preliminary results of our simulations of
what Gaia should be able to find in this field.Comment: Proceedings of the 19th European Workshop on White Dwarfs (Montr\'eal
11-15 August 2014). To appear on ASP Conference Series; 4 pages, 2 figure
White Dwarf Planets from GAIA
We investigate the potential of high-precision astrometry with GAIA for
detection of giant planetary companions to nearby white dwarfs. If one
considers that, to date, no confirmed planets around single white dwarfs are
known, the results from GAIA will be crucial to study the late-stage evolution
of planetary systems and to verify the possibility that 2nd-generation planets
are formed.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), 4 pages, 1 figur
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
Constraining the degree of the dominant mode in QQ Vir
We present early results of the application of a method which uses multicolor
photometry and spectroscopy for \ell discrimination. This method has been
successfully applied to the pulsating hot subdwarf Balloon 090100001. Here we
apply the method to QQ Vir (PG1325+101). This star was observed
spectroscopically and photometrically in 2008. Details on spectroscopy can be
found in Telting et al. (2010) while photometry and preliminary results on \ell
discrimination are provided here. The main aim of this work was to compare the
value of the \ell parameter derived for the main mode in QQ Vir to previously
published values derived by using different methods.Comment: Proceedings of The Fourth Meeting on Hot Subdwarf Stars and Related
Objects held in China, 20-24 July 2009. Accepted for publication in
Astrophysics and Space Scienc
Pulsating stars harbouring planets
Why bother with asteroseismology while studying exoplanets? There are several
answers to this question. Asteroseismology and exoplanetary sciences have much
in common and the synergy between the two opens up new aspects in both fields.
These fields and stellar activity, when taken together, allow maximum
extraction of information from exoplanet space missions. Asteroseismology of
the host star has already proved its value in a number of exoplanet systems by
its unprecedented precision in determining stellar parameters. In addition,
asteroseismology allows the possibility of discovering new exoplanets through
time delay studies. The study of the interaction between exoplanets and their
host stars opens new windows on various physical processes. In this review I
will summarize past and current research in exoplanet asteroseismology and
explore some guidelines for the future.Comment: 6 pages. To be published in Astrophysics and Space Science
Proceedings series (ASSP), in the proceedings of "20th Stellar Pulsation
Conference Series: Impact of new instrumentation & new insights in
stellar pulsations", 5-9 September 2011, Granada, Spain (English edition and
references update
Asteroseismic analysis of subdwarf B variable stars of KIC 10001893 and EPIC 220641886
KIC10001893 and EPIC220641886 are V1093Her type pulsating subdwarf-B stars, which were observed by the Kepler spacecraft during nominal and K2 mission respectively. The amplitude spectrum of both stars show similar characteristics that the majority of the pulsation frequencies lay in the gravity g-mode domain. While the g-mode region contains 248 frequencies, the p-mode region contains just 15, altogether indicating the hybrid nature of both stars. We used one of the seismic tools, asymptotic period spacing effectively to identify the modal degree of the majority of the modes. We could not find rotational multiplets for both stars which is likely due to pole-on orientation. We assigned dipole and quadrupole modes for KIC10001893, while for EPIC220641886 we defined modal degrees ranging from l=1 to l=12, apart from l=3 and l=11 modes, which are not seen
Discovery of a Nova-Like Cataclysmic Variable in the Kepler Mission Field
We announce the identification of a new cataclysmic variable star in the
field of the Kepler Mission, KIC J192410.81+445934.9. This system was
identified during a search for compact pulsators in the Kepler field.
High-speed photometry reveals coherent large-amplitude variability with a
period of 2.94 h. Rapid, large-amplitude quasi-periodic variations are also
detected on time scales of ~1200 s and ~650 s. Time-resolved spectroscopy
covering one half photometric period shows shallow, broad Balmer and He I
absorption lines with bright emission cores as well as strong He II and Bowen
blend emission. Radial velocity variations are also observed in the Balmer and
He I emission lines that are consistent with the photometric period. We
therefore conclude that KIC J192410.81+445934.9 is a nova-like variable of the
UX UMa class in or near the period gap, and it may belong to the rapidly
growing subclass of SW Sex systems. Based on 2MASS photometry and companion
star models, we place a lower limit on the distance to the system of ~500 pc.
Due to limitations of our discovery data, additional observations including
spectroscopy and polarimetry are needed to confirm the nature of this object.
Such data will help to further understanding of the behavior of nova-like
variables in the critical period range of 3-4 h, where standard cataclysmic
variable evolutionary theory finds major problems. The presence of this system
in the Kepler mission field-of-view also presents a unique opportunity to
obtain a continuous photometric data stream of unparalleled length and
precision on a cataclysmic variable system.Comment: Accepted for publication in the Astronomical Journal. 8 pages, 7
figures, uses emulateapj
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