1,722,864 research outputs found
Debris Disk around Star HR 8799
No full textThis infrared image, captured by the Spitzer Space Telescope shows a giant circle of very fine dust around the young star HR 8799, located to 129 light-years away in the constellation PegasusHave a prior knowledge about planetary systemEducação Superior::Ciências Exatas e da Terra::Astronomi
Debris Disk around Star HR 8799
No full textThis infrared image, captured by the Spitzer Space Telescope shows a giant circle of very fine dust around the young star HR 8799, located to 129 light-years away in the constellation PegasusHave a prior knowledge about planetary systemEducação Superior::Ciências Exatas e da Terra::Astronomi
Debris Disk around Star HR 8799
No full textThis infrared image, captured by the Spitzer Space Telescope shows a giant circle of very fine dust around the young star HR 8799, located to 129 light-years away in the constellation PegasusHave a prior knowledge about planetary systemEducação Superior::Ciências Exatas e da Terra::Astronomi
Debris Disk around Star HR 8799
No full textThis infrared image, captured by the Spitzer Space Telescope shows a giant circle of very fine dust around the young star HR 8799, located to 129 light-years away in the constellation PegasusHave a prior knowledge about planetary systemEducação Superior::Ciências Exatas e da Terra::Astronomi
Detection and Bulk Properties of the HR 8799 Planets with High-resolution Spectroscopy
Full text linkUsing the Keck Planet Imager and Characterizer, we obtained high-resolution (R ∼ 35,000) K-band spectra of the four planets orbiting HR 8799. We clearly detected H2O and CO in the atmospheres of HR 8799 c, d, and e, and tentatively detected a combination of CO and H2O in b. These are the most challenging directly imaged exoplanets that have been observed at high spectral resolution to date when considering both their angular separations and flux ratios. We developed a forward-modeling framework that allows us to jointly fit the spectra of the planets and the diffracted starlight simultaneously in a likelihood-based approach and obtained posterior probabilities on their effective temperatures, surface gravities, radial velocities, and spins. We measured v sin (i) values of 10.1-2.7+2.8km s-1 for HR 8799 d and 15.0-2.6+2.3 km s-1 for HR 8799 e, and placed an upper limit of <14 km s-1 of HR 8799 c. Under two different assumptions of their obliquities, we found tentative evidence that rotation velocity is anticorrelated with companion mass, which could indicate that magnetic braking with a circumplanetary disk at early times is less efficient at spinning down lower-mass planets. © 2021. The Author(s). Published by the American Astronomical Society.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
MOST light-curve analysis of the \u3b3 Doradus pulsator hr 8799, showing resonances and amplitude variations
No full textContext. The central star of the HR 8799 system is a \u3b3 Doradus-type pulsator. The system harbours four planetary-mass companions detected by direct imaging, and is a good solar system analogue. The masses of the companions are not accurately known because the estimation depends greatly on the age of the system, which is also not known with sufficient accuracy. Asteroseismic studies of the star might help to better constrain the age of HR 8799. We organized an extensive photometric and multi-site spectroscopic observing campaign to study the pulsations of the central star. Aims. The aim of the present study is to investigate the pulsation properties of HR 8799 in detail via the ultra-precise 47 d nearly continuous photometry obtained with the Microvariability and Oscillations in STars (MOST) space telescope, and to find as many independent pulsation modes as possible, which is the prerequisite for an asteroseismic age determination. Methods. We carried out Fourier analysis of the wide-band photometric time series. Results. We find that resonance and sudden amplitude changes characterize the pulsation of HR 8799. The dominant frequency is always at f1 = 1.978 d-1.Many multiples of one-ninth of the dominant frequency appear in the Fourier spectrum of the MOST data: n/9 f 1, where n = {1,2,3,4,5,6,7,8,9,10,13,14,17,18}. Our analysis also reveals that many of these peaks show strong amplitude decrease and phase variations even on the 47 d time scale. The dependencies between the pulsation frequencies of HR 8799 make the planned subsequent asteroseismic analysis rather difficult. We point out some resemblance between the light curve of HR 8799 and the modulated pulsation light curves of Blazhko RR Lyrae stars.Peer reviewed: YesNRC publication: Ye
The First Dynamical Mass Measurement in the HR 8799 System
Full text linkHR 8799 hosts four directly imaged giant planets, but none has a mass measured from first principles. We present the first dynamical mass measurement in this planetary system, finding that the innermost planet HR 8799 e has a mass of 9:6+1:9-1:8MJup. This mass results from combining the well-characterized orbits of all four planets with a new astrometric acceleration detection (5σ) from the Gaia EDR3 version of the Hipparcos-Gaia Catalog of Accelerations. We find with 95% confidence that HR 8799 e is below 13MJup, the deuterium-fusing mass limit. We derive a hot-start cooling age of 42+24-16 Myr for HR 8799 e that agrees well with its hypothesized membership in the Columba association but is also consistent with an alternative suggested membership in the β Pictoris moving group. We exclude the presence of any additional &5-MJup planets interior to HR 8799 e with semi-major axes between ≈3-16 au. We provide proper motion anomalies and a matrix equation to solve for the mass of any of the planets of HR 8799 using only mass ratios between the planets
Dynamical Mass of the Exoplanet Host Star HR 8799
No full textHR 8799 is a young A5/F0 star hosting four directly imaged giant planets at
wide separations (16-78 au) which are undergoing orbital motion and have
been continuously monitored with adaptive optics imaging since their discovery
over a decade ago. We present a dynamical mass of HR 8799 using 130 epochs of
relative astrometry of its planets, which include both published measurements
and new medium-band 3.1 m observations that we acquired with NIRC2 at Keck
Observatory. For the purpose of measuring the host star mass, each orbiting
planet is treated as a massless particle and is fit with a Keplerian orbit
using Markov chain Monte Carlo. We then use a Bayesian framework to combine
each independent total mass measurement into a cumulative dynamical mass using
all four planets. The dynamical mass of HR 8799 is 1.47 \Msun
assuming a uniform stellar mass prior, or 1.46 \Msun with a
weakly informative prior based on spectroscopy. There is a strong covariance
between the planets' eccentricities and the total system mass; when the
constraint is limited to low eccentricity solutions of , which is
motivated by dynamical stability, our mass measurement improves to
1.43 \Msun. Our dynamical mass and other fundamental measured
parameters of HR 8799 together with MESA Isochrones & Stellar Tracks grids
yields a bulk metallicity most consistent with [Fe/H] -0.25-0.00 dex and
an age of 10-23 Myr for the system. This implies hot start masses of 2.7-4.9
\Mjup for HR 8799 b and 4.1-7.0 \Mjup for HR 8799 c, d, and e, assuming they
formed at the same time as the host star.Comment: 23 pages, 13 figures, accepted to A
Recommended from our members
Deep thermal infrared imaging of HR 8799 bcde:new atmospheric constraints and limits on a fifth planet
No full textWe present new L′ (3.8 μm) and Brα (4.05 μm) data and reprocessed archival L′ data for the young, planet-hosting star HR 8799 obtained with Keck/NIRC2, VLT/NaCo, and Subaru/IRCS. We detect all four HR 8799 planets in each data set at a moderate to high signal-to-noise ratio (S/N ≳ 6-15). We fail to identify a fifth planet, "HR 8799 f," at r < 15 AU at a 5σ confidence level: one suggestive, marginally significant residual at 0.″2 is most likely a point-spread function artifact. Assuming companion ages of 30 Myr and the Baraffe planet cooling models, we rule out an HR 8799 f with a mass of 5 MJ (7 MJ ), 7 MJ (10 MJ ), or 12 MJ (13 MJ ) at r proj 12 AU, 9 AU, and 5 AU, respectively. All four HR 8799 planets have red early T dwarf-like L′-[4.05] colors, suggesting that their spectral energy distributions peak in between the L′ and M′ broadband filters. We find no statistically significant difference in HR 8799 cde's color. Atmosphere models assuming thick, patchy clouds appear to better match HR 8799 bcde's photometry than models assuming a uniform cloud layer. While non-equilibrium carbon chemistry is required to explain HR 8799 b and c's photometry/spectra, evidence for it from HR 8799 d and e's photometry is weaker. Future, deep-IR spectroscopy/spectrophotometry with the Gemini Planet Imager, SCExAO/CHARIS, and other facilities may clarify whether the planets are chemically similar or heterogeneous.</p
SNR for HR 8799 Ks and Lp data
No full text<p>SNR for HR 8799 bcde obtained for this data set and an earlier Ks band set also with Keck/NIRC2 and processed with various methods. Results: 1) . Advanced methods like A-LOCI and KLIP are required to detect HR 8799 e and yield deeper contrasts regardless of Strehl Ratio, in contrast to results reported by Wahhaj et al. (2013) and 2) A-LOCI offers a 20 to 60% contrast gain over KLIP (with a rotation gap) and runs just slightly slower.</p
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