| 1. |
- Hinkley, Sasha, et al.
(författare)
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The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems
- 2022
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1039
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Tidskriftsartikel (refereegranskat)abstract
- The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ∼15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles.
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| 2. |
- Sneden, Christopher, et al.
(författare)
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Chemical Compositions of Red Giant Stars from Habitable Zone Planet Finder Spectroscopy
- 2021
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 161:3
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Tidskriftsartikel (refereegranskat)abstract
- We have used the Habitable Zone Planet Finder (HPF) to gather high-resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal branch (RHB) stars, one open cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81-1.28 mu m wavelength range of the zyJ bands, partially filling the gap between the optical (0.4-1.0 mu m) and infrared (1.5-2.4 mu m) spectra already available for the program stars. We derive abundances of 17 species from LTE-based computations involving equivalent widths and spectrum syntheses, and estimate abundance corrections for the species that are most affected by departures from LTE in RHB stars. Generally good agreement is found between HPF-based metallicities and abundance ratios and those from the optical and infrared spectral regions. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C i, P i, S i, K i). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extreme carbon isotope ratio, and one with a rare, very large lithium content. The latter star is unique in our sample in exhibiting very strong He i 10830 A absorption. The abundances of the open cluster giant concur with those derived from other wavelength regions. Detections of C i and S i in HD 122563 are reported, yielding the lowest metallicity determination of [S/Fe] from more than one multiplet.
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| 3. |
- Sneden, Christopher, et al.
(författare)
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The Active Chromospheres of Lithium-rich Red Giant Stars
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 940:1
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Tidskriftsartikel (refereegranskat)abstract
- We have gathered near-infrared zyJ-band high-resolution spectra of nearly 300 field red giant stars with known lithium abundances in order to survey their He i λ10830 absorption strengths. This transition is an indicator of chromospheric activity and/or mass loss in red giants. The majority of stars in our sample reside in the red clump or red horizontal branch based on their V − J, MV color–magnitude diagram, and Gaia Teff and log(g) values. Most of our target stars are Li-poor in the sense of having normally low Li abundances, defined here as log ò(Li) < 1.25. Over 90% of these Li-poor stars have weak λ10830 features. However, more than half of the 83 Li-rich stars (log ò(Li) > 1.25) have strong λ10830 absorptions. These large λ10830 lines signal excess chromospheric activity in Li-rich stars; there is almost no indication of significant mass loss. The Li-rich giants may also have a higher binary fraction than Li-poor stars, based on their astrometric data. It appears likely that both residence on the horizontal branch and present or past binary interaction play roles in the significant Li–He connection established in this survey.
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| 4. |
- Llop-Sayson, Jorge, et al.
(författare)
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Constraining the Orbit and Mass of epsilon Eridani b with Radial Velocities, Hipparcos IAD-Gaia DR2 Astrometry, and Multiepoch Vortex Coronagraphy Upper Limits
- 2021
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Ingår i: Astronomical Journal. - : Institute of Physics Publishing (IOPP). - 0004-6256 .- 1538-3881. ; 162:5
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Tidskriftsartikel (refereegranskat)abstract
- epsilon Eridani is a young planetary system hosting a complex multibelt debris disk and a confirmed Jupiter-like planet orbiting at 3.48 au from its host star. Its age and architecture are thus reminiscent of the early Solar System. The most recent study of Mawet et al., which combined radial-velocity data and Ms-band direct imaging upper limits, started to constrain the planet's orbital parameters and mass, but are still affected by large error bars and degeneracies. Here we make use of the most recent data compilation from three different techniques to further refine epsilon Eridani b's properties: RVs, absolute astrometry measurements from the Hipparcos and Gaia missions, and new Keck/NIRC2 Ms-band vortex coronagraph images. We combine this data in a Bayesian framework. We find a new mass, M-b = 0.66(-0.09)(+0.12) M-Jup, and inclination, i = 78.81(-22.41 degrees)(+29.34), with at least a factor 2 of improvement over previous uncertainties. We also report updated constraints on the longitude of the ascending node, the argument of the periastron, and the time of periastron passage. With these updated parameters, we can better predict the position of the planet at any past and future epoch, which can greatly help define the strategy and planning of future observations and with subsequent data analysis. In particular, these results can assist the search for a direct detection with JWST and the Nancy Grace Roman Space Telescope's coronagraph instrument.
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| 5. |
- Tran, Quang H., et al.
(författare)
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TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to Have Originated from High-eccentricity Migration
- 2022
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 163:5
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of two transiting planets around the bright (V = 9.9 mag) main-sequence F7 star TOI-1670 by the Transiting Exoplanet Survey Satellite. TOI-1670 b is a sub-Neptune (R-b = 2.06(-0.15)(+0.19) R-circle plus) on a 10.9 day orbit, and TOI-1670 c is a warm Jupiter (R-c= 0.987(-0.025)(+0.025) R-Jup) on a 40.7 day orbit. Using radial velocity observations gathered with the Tull Coude Spectrograph on the Harlan J. Smith telescope and HARPS-N on the Telescopio Nazionale Galileo, we find a planet mass of M-c = 0.63(-0.08)(+0.09) M(Jup )for the outer warm Jupiter, implying a mean density of rho(c) = 0.81(-0.11)(+0.13) g cm(-3). The inner sub-Neptune is undetected in our radial velocity data (M-b < 0.13 M-Jup at the 99% confidence level). Multiplanet systems like TOI-1670 hosting an outer warm Jupiter on a nearly circular orbit (l(e) = 0.09(-0.04)(+0.05)) and one or more inner coplanar planets are more consistent with "gentle" formation mechanisms such as disk migration or in situ formation rather than high-eccentricity migration. Of the 11 known systems with a warm Jupiter and a smaller inner companion, eight (73%) are near a low-order mean-motion resonance, which can be a signature of migration. TOI-1670 joins two other systems (27% of this subsample) with period commensurabilities greater than 3, a common feature of in situ formation or halted inward migration. TOI-1670 and the handful of similar systems support a diversity of formation pathways for warm Jupiters.
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