AffiliationUniv Arizona, Dept Astron
Univ Arizona, Steward Observ
planets and satellites: atmospheres
planets and satellites: composition
planets and satellites: detection
planets and satellites: terrestrial planets
techniques: radial velocities
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationLópez-Morales, M., Ben-Ami, S., Gonzalez-Abad, G., Garcia-Mejia, J., Dietrich, J., & Szentgyorgyi, A. (2019). Optimizing Ground-based Observations of O2 in Earth Analogs. The Astronomical Journal, 158(1), 24.
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AbstractWe present the result of calculations to optimize the search for molecular oxygen, O-2, in Earth analogs transiting around nearby, low-mass stars using ground-based, high-resolution Doppler shift techniques. We investigate a series of parameters, namely spectral resolution, wavelength coverage of the observations, and sky coordinates and systemic velocity of the exoplanetary systems, to find the values that optimize detectability of O-2. We find that increasing the spectral resolution of observations to R similar to 300,000-400,000 from the typical R similar to 100,000 more than doubles the average depth of O-2 lines in planets with atmospheres similar to Earth's. Resolutions higher than similar to 500,000 do not produce significant gains in the depths of the O-2 lines. We confirm that observations in the O-2 A-band are the most efficient except for M9V host stars, for which observations in the O-2 near-infrared (NIR) band are more efficient. Combining observations in the O-2 A, B, and NIR bands can reduce the number of transits needed to produce a detection of O-2 by about one-third in the case of white noise limited observations. However, that advantage disappears in the presence of typical levels of red noise. Therefore, combining observations in more than one band produces no significant gain versus observing only in the A band, unless red noise can be significantly reduced. Blending between the exoplanet's O-2 lines and telluric O-2 lines is a known problem. We find that problem can be alleviated by increasing the resolution of the observations, and by giving preference to targets near the ecliptic.
VersionFinal published version
SponsorsBrinson Foundation; Smithsonian Institution; National Science Foundation [DGE1745303]; Ford Foundation through a Ford Foundation Predoctoral Fellowship
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Precise radial velocities of giant starsOrtiz, Mauricio; Reffert, Sabine; Trifonov, Trifon; Quirrenbach, Andreas; Mitchell, David S.; Nowak, Grzegorz; Buenzli, Esther; Zimmerman, Neil; Bonnefoy, Mickaël; Skemer, Andy; et al. (EDP SCIENCES S A, 2016-10-28)Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.
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