33 research outputs found
Precise radial velocities of giant stars VIII. Testing for the presence of planets with CRIRES Infrared Radial Velocities
We have been monitoring 373 very bright (V < 6 mag) G and K giants with high
precision optical Doppler spectroscopy for more than a decade at Lick
Observatory. Our goal was to discover planetary companions around those stars
and to better understand planet formation and evolution around
intermediate-mass stars. However, in principle, long-term, g-mode nonradial
stellar pulsations or rotating stellar features, such as spots, could
effectively mimic a planetary signal in the radial velocity data. Our goal is
to compare optical and infrared radial velocities for those stars with periodic
radial velocity patterns and to test for consistency of their fitted radial
velocity semiamplitudes. Thereby, we distinguish processes intrinsic to the
star from orbiting companions as reason for the radial velocity periodicity
observed in the optical. Stellar spectra with high spectral resolution have
been taken in the H-band with the CRIRES near-infrared spectrograph at ESO's
VLT for 20 stars of our Lick survey. Radial velocities are derived using many
deep and stable telluric CO2 lines for precise wavelength calibration. We find
that the optical and near-infrared radial velocities of the giant stars in our
sample are consistent. We present detailed results for eight stars in our
sample previously reported to have planets or brown dwarf companions. All eight
stars passed the infrared test. We conclude that the planet hypothesis provides
the best explanation for the periodic radial velocity patterns observed for
these giant stars.Comment: 14 pages, 6 figures, 3 tables, accepted by Astronomy & Astrophysic
Precision Radial Velocity Surveys for Exoplanets
Seit den 90-ziger Jahren haben Astronomen etwa 500 extrasolare Planeten entdeckt. Die meisten von Ihnen wurden mit der Radialgeschwindigkeits-Methode gefunden. In dieser Arbeit prĂ€sentieren wir unsere prĂ€zisen Radialgeschwindigkeitsmessungen fĂŒr ein Sample von 40 M-Sternen und 30 sonnenĂ€hnlichen Sternen. Die DatensĂ€tze stammen von vier verschieden Instrumenten (UVES, CES+LC, CES+VLC, und HARPS) und werden auf Hinweise von Planeten untersucht. Dazu fĂŒhren wir statistische Tests zu ExzessvariabilitĂ€ten, Langzeittrends und PeriodizitĂ€ten durch. FĂŒr letzteren Zweck, haben wir ein hĂ€ufig genutztes Werkzeug fĂŒr die Periodenanalyse, das sogenannte Lomb-Scargle Periodogramm, weiterentwickelt. Unsere Radialgeschwindigkeitsgenaukeit von wenigen m/s ist annĂ€hernd ausreichend fĂŒr die angestrebten Ziele, nĂ€mlich die Suche nach terrestrischen Planeten in der habitablen Zone von M-Sternen und die Suche nach Jupiter-artigen Planeten um sonnenĂ€hnliche Sterne. Wir demonstrieren dies mit oberen Massengrenzen. Aus unserer Datenanalyse geht kein neuer Planet hervor, wĂ€hrend wir die bereits bekannten Planeten fĂŒr die sonnenĂ€hnlichen Sterne Iota Hor und HR 506 sowie den Langzeittrend fĂŒr Eps Ind A bestĂ€tigen können. DarĂŒber hinaus konnten wir einige Doppelsterne und einen Braunen Zwerg identfizieren. Unsere Ergebnisse stimmen mit den Erwartungen fĂŒr die HĂ€ufigkeit von Jupiter-artigen Planeten ĂŒberein, welche etwa 1% fĂŒr M-Sterne und 10% fĂŒr sonnenĂ€hnliche Sterne ist
The Discovery of Stellar Oscillations in the Planet Hosting Giant Star Beta Geminorum
We present the results of a long time series of precise stellar radial
velocity measurements of the planet hosting K giant star Beta Geminorum. A
total of 20 hours of observations spanning three nights were obtained and the
radial velocity variations show the presence of solar-like stellar
oscillations. Our period analysis yields six significant pulsation modes that
have frequencies in the range of 30 - 150 microHz. The dominant mode is at a
frequency of 86.9 microHz and has an amplitude of 5.3 m/s. These values are
consistent with stellar oscillations for a giant star with a stellar mass of
approximately 2 solar masses. This stellar mass implies a companion minimum
mass of 2.6 Jupiter masses. Beta Gem is the first planet hosting giant star in
which multi-periodic stellar oscillations have been detected. The study of
stellar oscillations in planet hosting giant stars may provide an independent,
and more accurate determination of the stellar mass.Comment: 12 pages preprint, 2 figures, accepted by ApJ Letter
New HARPS and FEROS observations of GJ1046
In this paper we present new precise Doppler data of GJ1046 taken between
November 2005 and July 2018 with the HARPS and the FEROS high-resolution
spectographs. In addition, we provide a new stellar mass estimate of GJ1046 and
we update the orbital parameters of the GJ1046 system. These new data and
analysis could be used together with the GAIA epoch astrometry, when available,
for braking the degeneracy and revealing the true mass of the GJ1046
system.Comment: 2 pages, 1 figure, 1 table with RV data (available only in the
Astro-PH version of the paper), Accepted by RNAA
Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b
Hot gas giant exoplanets can lose part of their atmosphere due to strong
stellar irradiation, affecting their physical and chemical evolution. Studies
of atmospheric escape from exoplanets have mostly relied on space-based
observations of the hydrogen Lyman-{\alpha} line in the far ultraviolet which
is strongly affected by interstellar absorption. Using ground-based
high-resolution spectroscopy we detect excess absorption in the helium triplet
at 1083 nm during the transit of the Saturn-mass exoplanet WASP-69b, at a
signal-to-noise ratio of 18. We measure line blue shifts of several km/s and
post transit absorption, which we interpret as the escape of part of the
atmosphere trailing behind the planet in comet-like form.
[Additional notes by authors: Furthermore, we provide upper limits for helium
signals in the atmospheres of the exoplanets HD 209458b, KELT-9b, and GJ 436b.
We investigate the host stars of all planets with detected helium signals and
those of the three planets we derive upper limits for. In each case we
calculate the X-ray and extreme ultraviolet flux received by these planets. We
find that helium is detected in the atmospheres of planets (orbiting the more
active stars and) receiving the larger amount of irradiation from their host
stars.]Comment: Submitted to Science on 14 March 2018; Accepted by Science on 16
November 2018; Published by Science on 6 December 2018. This is the author's
version of the work. It is posted here by permission of the AAAS for personal
use. The definitive version was published in Science, on 6 December 2018 -
Report: pages 21 (preprint), 4 figures - Supplementary materials: 22 pages,
10 figures, 3 table
Practices to support co-design processes: A case-study of co-designing a program for children with parents with a mental health problem in the Austrian region of Tyrol
Forms of collaborative knowledge production, such as community-academic partnerships (CAP), have been increasingly used in health care. However, instructions on how to deliver such processes are lacking. We aim to identify practice ingredients for one element within a CAP, a 6-month co-design process, during which 26 community- and 13 research-partners collaboratively designed an intervention programme for children whose parent have a mental illness. Using 22 published facilitating and hindering factors for CAP as the analytical framework, eight community-partners reflected on the activities which took place during the co-design process. From a qualitative content analysis of the data, we distilled essential practices for each CAP factor. Ten community- and eight research-partners revised the results and co-authored this article. We identified 36 practices across the 22 CAP facilitating or hindering factors. Most practices address more than one factor. Many practices relate to workshop design, facilitation methods, and relationship building. Most practices were identified for facilitating âtrust among partnersâ, âshared visions, goals and/or missionsâ, âeffective/frequent communicationâ, and âwell-structured meetingsâ. Fewer practices were observed for âeffective conflict resolutionâ, âpositive community impactâ and for avoiding âexcessive funding pressure/control strugglesâ and âhigh burden of activitiesâ. Co-designing a programme for mental healthcare is a challenging process that requires skills in process management and communication. We provide practice steps for delivering co-design activities. However, practitioners may have to adapt them to different cultural contexts. Further research is needed to analyse whether co-writing with community-partners results in a better research output and benefits for participants