Based on the long-term radial velocity surveys carried out with the McDonald Observatory 2.7 m Harlan J. Smith Telescope from 1988 to the present, we derive upper limits to long-period giant planet ...companions for 31 nearby stars. Data from three phases of the McDonald Observatory 2.7 m planet-search program have been merged together, and for 17 objects data from the pioneering Canada-France-Hawaii Telescope radial velocity program have also been included in the companion-limits determination. For those 17 objects, the baseline of observations is in excess of 23 yr, enabling the detection or exclusion of giant planets in orbits beyond 8 AU. We also consider the possibility of eccentric orbits in our computations. At an orbital separation of 5.2 AU, we can exclude on average planets of M sin i MJ (e = 0) and M sin i MJ (e = 0.6) for 25 of the 31 stars in this survey. However, we are not yet able to rule out 'true Jupiters,' i.e., planets of M sin i ~ 1MJ in 5.2 AU orbits. These limits are of interest for the Space Interferometry Mission, Terrestrial Planet Finder, and Darwin missions, which will search for terrestrial planets orbiting nearby stars, many of which are included in this work.
A DETECTION OF Hα IN AN EXOPLANETARY EXOSPHERE JENSEN, Adam G; REDFIELD, Seth; ENDL, Michael ...
Astrophysical journal/The Astrophysical journal,
06/2012, Volume:
751, Issue:
2
Journal Article
Peer reviewed
Open access
We report on a search for H alpha absorption in four exoplanets. Strong features at H alpha are observed in the transmission spectra of both HD 189733b and HD 209458b. We attempt to characterize and ...remove the effects of stellar variability in HD 189733b, and along with an empirical Monte Carlo test the results imply a statistically significant transit-dependent feature of (-8.72 + or - 1.48) x 10 super(-4) integrated over a 16A band relative to the adjacent continuum. We explore these assumptions and argue that T sub(exc) is very likely much greater than the radiative equilibrium temperature (the temperature the planet is assumed to be at based on stellar radiation and the planetary distance) of HD 189733b. We argue that the n = 2 hydrogen required to cause H alpha absorption in the atmosphere is created as a result of the greater UV flux at HD 189733b, which has the smallest orbit and most chromospherically active central star in our sample.
Kea Endl, Michael; Cochran, William D.
Publications of the Astronomical Society of the Pacific,
09/2016, Volume:
128, Issue:
967
Journal Article
Peer reviewed
In this paper, we describe Kea a new spectroscopic fitting method to derive stellar parameters from moderate to low signal-to-noise, high-resolution spectra. We developed this new tool to analyze the ...massive data set of the Kepler mission reconnaissance spectra that we have obtained at McDonald Observatory. We use Kea to determine effective temperatures (T
eff), metallicity (Fe/H), surface gravity (log g), and projected rotational velocity (v sin i). Kea compares the observations to a large library of synthetic spectra that covers a wide range of different T
eff, Fe/H, and log g values. We calibrated Kea on observations of well-characterized standard stars (the Kepler field “platinum” sample) that range in T
eff from 5000 to 6500 K, in Fe/H from −0.5 to +0.4 dex, and in log g from 3.2 to 4.6 dex. We then compared the Kea results from reconnaissance spectra of 45 Kepler objects of interest (KOIs) to stellar parameters derived from higher signal-to-noise spectra obtained with Keck/HIRES. We find typical uncertainties of 100 K in T
eff, 0.12 dex in Fe/H, and 0.18 dex in log g.
In this paper, we describe Kea a new spectroscopic fitting method to derive stellar parameters from moderate to low signal-to-noise, high-resolution spectra. We developed this new tool to analyze the ...massive data set of the Kepler mission reconnaissance spectra that we have obtained at McDonald Observatory. We use Kea to determine effective temperatures (Teff), metallicity (Fe/H), surface gravity (log g), and projected rotational velocity ( v sin i ). Kea compares the observations to a large library of synthetic spectra that covers a wide range of different Teff, Fe/H, and log g values. We calibrated Kea on observations of well-characterized standard stars (the Kepler field "platinum" sample) that range in Teff from 5000 to 6500 K, in Fe/H from −0.5 to +0.4 dex, and in log g from 3.2 to 4.6 dex. We then compared the Kea results from reconnaissance spectra of 45 Kepler objects of interest (KOIs) to stellar parameters derived from higher signal-to-noise spectra obtained with Keck/HIRES. We find typical uncertainties of 100 K in Teff, 0.12 dex in Fe/H, and 0.18 dex in log g.
Understanding the dynamics and kinematics of outflowing atmospheres of hot and warm exoplanets is crucial to understanding the origins and evolutionary history of the exoplanets near the evaporation ...desert. Recently, ground-based measurements of the meta-stable helium atom's resonant absorption at 10830 has become a powerful probe of the base environment which is driving the outflow of exoplanet atmospheres. We report evidence for the He i 10830 in absorption (equivalent width ∼0.012 0.002 ) in the exosphere of a warm Neptune orbiting the M-dwarf GJ 3470, during three transits using the Habitable Zone Planet Finder near-infrared spectrograph. This marks the first reported evidence for He i 10830 atmospheric absorption for a planet orbiting an M-dwarf. Our detected absorption is broad and its blueshifted wing extends to −36 km s−1, the largest reported in the literature to date. We modeled the state of helium atoms in the exosphere of GJ3470b based on assumptions on the UV and X-ray flux of GJ 3470, and found our measurement of flux-weighted column density of meta-stable state helium , derived from our transit observations, to be consistent with the model, within its uncertainties. The methodology developed here will be useful to study and constrain the atmospheric outflow models of other exoplanets like GJ 3470b, which are near the edge of the evaporation desert.
We report the discovery of a Neptune-sized ( ) transiting circumbinary planet, Kepler-1661 b, found in the Kepler photometry. The planet has a period of ∼175 days and its orbit precesses with a ...period of only 35 yr. The precession causes the alignment of the orbital planes to vary, and the planet is in a transiting configuration only ∼7% of the time as seen from Earth. As with several other Kepler circumbinary planets, Kepler-1661 b orbits close to the stability radius, and is near the (hot) edge of the habitable zone. The planet orbits a single-lined, grazing eclipsing binary, containing a 0.84 and 0.26 pair of stars in a mildly eccentric (e = 0.11), 28.2 day orbit. The system is fairly young, with an estimated age of ∼1-3 Gyr, and exhibits significant starspot modulations. The grazing eclipse configuration means the system is very sensitive to changes in the binary inclination, which manifests itself as a change in the eclipse depth. The starspots contaminate the eclipse photometry, but not in the usual way of inducing spurious eclipse timing variations. Rather, the starspots alter the normalization of the light curve, and hence the eclipse depths. This can lead to spurious eclipse depth variations, which are then incorrectly ascribed to binary orbital precession.
ABSTRACT Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot ...Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric H detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Rp. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of Beq = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.
At a distance of 1.295 parsecs, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun's closest stellar neighbour and one of the best-studied low-mass stars. ...It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface.
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