77 research outputs found
A Search for Planets with SALT
As the SALT High Resolution Spectrograph completion is nearing we plan to
extend the Pennsylvania-Torun Planets Search (PTPS) with HET to the southern
hemisphere. Due to overlap of the skies available for both HET and SALT in the
declination range (+10, -10) deg some cooperation and immediate follow up is
possible. Here we present, as an example, a 1000 star sample of evolved
stars for the future SALT Planet Search.Comment: 6 pages, 2 figure
Red giants from the Pennsylvania - Torun Planet Search
The main goal of the Pennsylvania - Torun Planet Search (PTPS) is detection
and characterization of planets around evolved stars using the high-accuracy
radial velocity (RV) technique. The project is performed with the 9.2 m
Hobby-Eberly Telescope. To determine stellar parameters and evolutionary status
for targets observed within the survey complete spectral analysis of all
objects is required. In this paper we present the atmospheric parameters
(effective temperatures, surface gravities, microturbulent velocities and
metallicities) of a subsample of Red Giant Clump stars using strictly
spectroscopic methods based on analysis of equivalent widths of Fe I and Fe II
lines. It is shown that our spectroscopic approach brings reliable and
consistent results.Comment: 3 pages, 2 figures, proceeding of the conference "New Technologies
for Probing the Diversity of Brown Dwarfs and Exoplanets" (Shangai, China,
July 19-24, 2009), to appear in EPJ Web of Conference
The Penn State - Toru\'n Centre for Astronomy Planet Search stars IV. Dwarfs and the complete sample
Our knowledge of the intrinsic parameters of exoplanets is as precise as our
determinations of their stellar hosts parameters. In the case of radial
velocity searches for planets, stellar masses appear to be crucial. But before
estimating stellar masses properly, detailed spectroscopic analysis is
essential. With this paper we conclude a general spectroscopic description of
the Pennsylvania-Torun Planet Search (PTPS) sample of stars. We aim at a
detailed description of basic parameters of stars representing the complete
PTPS sample. We present atmospheric and physical parameters for dwarf stars
observed within the PTPS along with updated physical parameters for the
remaining stars from this sample after the first Gaia data release. We used
high resolution (R=60 000) and high signal-to-noise-ratio (S/N=150-250) spectra
from the Hobby-Eberly Telescope and its High Resolution Spectrograph. Stellar
atmospheric parameters were determined through a strictly spectroscopic local
thermodynamic equilibrium analysis (LTE) of the equivalent widths of FeI and
FeII lines. Stellar masses, ages, and luminosities were estimated through a
Bayesian analysis of theoretical isochrones. We present , log ,
[Fe/H], micrturbulence velocities, absolute radial velocities, and rotational
velocities for 156 stars from the dwarf sample of PTPS. For most of these stars
these are the first determinations. We refine the definition of PTPS subsamples
of stars (giants, subgiants, and dwarfs) and update the luminosity classes for
all PTPS stars. Using available Gaia and Hipparcos parallaxes, we redetermine
the stellar parameters (masses, radii, luminosities, and ages) for 451 PTPS
stars. The complete PTPS sample of 885 stars is composed of 132 dwarfs, 238
subgiants, and 515 giants, of which the vast majority are of roughly solar
mass.Comment: 11 pages, 10 figures, Accepted for publication in Astronomy &
Astrophysic
The Penn State - Toru\'n Planet Search: target characteristics and recent results
More than 450 stars hosting planets are known today but only approximately 30
planetary systems were discovered around stars beyond the Main Sequence. The
Penn State-Toru\'n Planet Search, putting an emphasis on extending studies of
planetary system formation and evolution to intermediate-mass stars, is
oriented towards the discoveries of substellar-mass companions to a large
sample of evolved stars using high-precision radial velocity technique. We
present the recent status of our survey and detailed characteristic for ~350
late type giant stars, i.e. the new results of radial velocity analysis and
stellar fundamental parameters obtained with extensive spectroscopic method.
Moreover, in the future we will make an attempt to perform the statistical
study of our sample and searching the correlations between the existence of
substellar objects and stellar atmospheric parameters according to previous
works which investigated the planetary companion impact on the evolution of the
host stars.Comment: 7 pages, 5 figures, proceeding of the conference "Planetary Systems
beyond the Main Sequence" (Bamberg, Germany, August 11-14, 2010) edited by S.
Schuh, H. Drechsel and U. Heber, AIP Conference Series, part of
PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.660
Planets Around the K-Giants BD+20 274 and HD 219415
We present the discovery of planet-mass companions to two giant stars by the
ongoing Penn State- Toru\'n Planet Search (PTPS) conducted with the 9.2 m
Hobby-Eberly Telescope. The less massive of these stars, K5-giant BD+20 274,
has a 4.2 MJ minimum mass planet orbiting the star at a 578-day period and a
more distant, likely stellar-mass companion. The best currently available model
of the planet orbiting the K0-giant HD 219415 points to a Jupiter-mass
companion in a 5.7-year, eccentric orbit around the star, making it the longest
period planet yet detected by our survey. This planet has an amplitude of
\sim18 m/s, comparable to the median radial velocity (RV) "jitter", typical of
giant stars.Comment: 5 figures, 13 pages, accepted by the Astrophysical Journal. arXiv
admin note: substantial text overlap with arXiv:1110.164
Three red giants with substellar-mass companions
We present three giant stars from the ongoing Penn State-Toru\'n Planet
Search with the Hobby-Eberly Telescope, which exhibit radial velocity
variations that point to a presence of planetary --mass companions around them.
BD+49 828 is a K0 giant with a = minimum mass companion in
AU (d),
orbit. HD 95127, a log/=,
, K0 giant has a = minimum mass companion in
AU (d), orbit.
Finally, HD 216536, is a K0 giant with a minimum mass companion in
AU (d),
orbit. Both, HD 95127 b and HD 216536 b in their
compact orbits, are very close to the engulfment zone and hence prone to
ingestion in the near future. BD+49 828 b is among the longest period planets
detected with the radial velocity technique until now and it will remain
unaffected by stellar evolution up to a very late stage of its host. We discuss
general properties of planetary systems around evolved stars and planet
survivability using existing data on exoplanets in more detail.Comment: 47 pages, 11 figures. Accepted by Ap
TAPAS IV. TYC 3667-1280-1 b - the most massive red giant star hosting a warm Jupiter
We present the latest result of the TAPAS project that is devoted to intense
monitoring of planetary candidates that are identified within the
PennState-Toru\'n planet search.
We aim to detect planetary systems around evolved stars to be able to build
sound statistics on the frequency and intrinsic nature of these systems, and to
deliver in-depth studies of selected planetary systems with evidence of
star-planet interaction processes.
The paper is based on precise radial velocity measurements: 13 epochs
collected over 1920 days with the Hobby-Eberly Telescope and its
High-Resolution Spectrograph, and 22 epochs of ultra-precise HARPS-N data
collected over 961 days.
We present a warm-Jupiter (, 0.4)
companion with an orbital period of 26.468 days in a circular () orbit
around a giant evolved (, ) star
with . This is the most massive and oldest star
found to be hosting a close-in giant planet. Its proximity to its host
() means that the planet has a probability of
transits; this calls for photometric follow-up study.
This massive warm Jupiter with a near circular orbit around an evolved
massive star can help set constraints on general migration mechanisms for warm
Jupiters and, given its high equilibrium temperature, can help test energy
deposition models in hot Jupiters.Comment: 5 pages, 3 figures, accepted by A&
TAPAS - Tracking Advanced Planetary Systems with HARPS-N. II. Super Li-rich giant HD 107028
Lithium rich giant stars are rare objects. For some of them, Li enrichment
exceeds abundance of this element found in solar system meteorites, suggesting
that these stars have gone through a Li enhancement process. We identified a Li
rich giant HD 107028 with A(Li) > 3.3 in a sample of evolved stars observed
within the PennState Torun Planet Search. In this work we study different
enhancement scenarios and we try to identify the one responsible for Li
enrichment for HD 107028. We collected high resolution spectra with three
different instruments, covering different spectral ranges. We determine stellar
parameters and abundances of selected elements with both equivalent width
measurements and analysis, and spectral synthesis. We also collected multi
epoch high precision radial velocities in an attempt to detect a companion.
Collected data show that HD 107028 is a star at the base of Red Giant Branch.
Except for high Li abundance, we have not identified any other anomalies in its
chemical composition, and there is no indication of a low mass or stellar
companion. We exclude Li production at the Luminosity Function Bump on RGB, as
the effective temperature and luminosity suggest that the evolutionary state is
much earlier than RGB Bump. We also cannot confirm the Li enhancement by
contamination, as we do not observe any anomalies that are associated with this
scenario. After evaluating various scenarios of Li enhancement we conclude that
the Li-overabundance of HD 107028 originates from Main Sequence evolution, and
may be caused by diffusion process.Comment: Accepted for publication in A&
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. III. HD 5583 and BD+15 2375 - two cool giants with warm companions
Evolved stars are crucial pieces to understand the dependency of the planet
formation mechanism on the stellar mass and to explore deeper the mechanism
involved in star-planet interactions. Over the past ten years, we have
monitored about 1000 evolved stars for radial velocity variations in search for
low-mass companions under the Penn State - Torun Centre for Astronomy Planet
Search program with the Hobby-Eberly Telescope. Selected prospective candidates
that required higher RV precision measurements have been followed with HARPS-N
at the 3.6 m Telescopio Nazionale Galileo under the TAPAS project.
We aim to detect planetary systems around evolved stars to be able to build
sound statistics on the frequency and intrinsic nature of these systems, and to
deliver in-depth studies of selected planetary systems with evidence of
star-planet interaction processes. For HD 5583 we obtained 14 epochs of precise
RV measurements collected over 2313 days with the Hobby-Eberly Telescope (HET),
and 22 epochs of ultra-precise HARPS-N data collected over 976 days. For BD+15
2375 we collected 24 epochs of HET data over 3286 days and 25 epochs of HARPS-S
data over 902 days.
We report the discovery of two planetary mass objects orbiting two evolved
Red Giant stars: HD~5583 has a m sin i = 5.78 M companion at 0.529~AU in
a nearly circular orbit (e=0.076), the closest companion to a giant star
detected with the RV technique, and BD+15~2735 that with a m sin i= 1.06
M holds the record of the lightest planet found so far orbiting an
evolved star (in a circular e=0.001, 0.576~AU orbit). These are the third and
fourth planets found within the TAPAS project, a HARPS-N monitoring of evolved
planetary systems identified with the Hobby-Eberly Telescope.Comment: 9 pages, 6 figures. Accepted by Astronomy and Astrophysic
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