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Register a new userA High Eccentricity Component in the Double Planet System Around HD 163607 and a Planet Around HD 164509
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We report the detection of three new exoplanets from Keck Observatory. HD 163607 is a metal-rich G5IV star with two planets. The inner planet has an observed orbital period of 75.29 $pm$ 0.02 days, a semi-amplitude of 51.1 $pm$ 1.4 ms, an eccentricity of 0.73 $pm$ 0.02 and a derived minimum mass of msini = 0.77 $pm$ 0.02 mjup. This is the largest eccentricity of any known planet in a multi-planet system. The argument of periastron passage is 78.7 $pm$ 2.0$^{circ}$; consequently, the planets closest approach to its parent star is very near the line of sight, leading to a relatively high transit probability of 8%. The outer planet has an orbital period of 3.60 $pm$ 0.02 years, an orbital eccentricity of 0.12 $pm$ 0.06 and a semi-amplitude of 40.4 $pm$ 1.3 ms. The minimum mass is msini = 2.29 $pm$ 0.16 mjup. HD 164509 is a metal-rich G5V star with a planet in an orbital period of 282.4 $pm$ 3.8 days and an eccentricity of 0.26 $pm$ 0.14. The semi-amplitude of 14.2 $pm$ 2.7 ms implies a minimum mass of 0.48 $pm$ 0.09 mjup. The radial velocities of HD 164509 also exhibit a residual linear trend of -5.1 $pm$ 0.7 ms per year, indicating the presence of an additional longer period companion in the system. Photometric observations demonstrate that HD 163607 and HD 164509 are constant in brightness to sub-millimag levels on their radial velocity periods. This provides strong support for planetary reflex motion as the cause of the radial velocity variations.
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The Geneva group has reported two Saturn-mass planets orbiting HD 83443 (K0V) with periods of 2.98 and 29.8 d. The two planets have raised interest in their dynamics because of the possible 10:1 orbital resonance and the strong gravitational interactions. We report precise Doppler measurements of HD 83443 obtained with the Keck/HIRES and the AAT/UCLES spectrometers. These measurements strongly confirm the inner planet with period of 2.985 d, with orbital parameters in very good agreement with those of the Geneva group. However these Doppler measurements show no evidence of the outer planet, at thresholds of 1/4 (3 m/s) of the reported velocity amplitude of 13.8 m/s. Thus, the existence of the outer planet is in question. Indeed, the current Doppler measurements reveal no evidence of any second planet with periods less than a year.
Precise radial velocities from the Anglo-Australian Telescope confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P=89.1+/-0.1 days, and m sin i=1.35+/-0.17 Mjup. These data also confirm the planetary nature of the outer companion, with m sin i=3.9+/-0.6 Mjup and a=2.96+/-0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.
Young planets are expected to cause perturbations in protostellar disks that may be used to infer their presence. Clear detection of still-forming planets embedded within gas-rich disks is rare. HD 169142 is a very young Herbig Ae-Be star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects around this star have been made previously, follow-up studies remain inconclusive. We used SPHERE at ESO VLT to obtain a sequence of high-contrast images of the immediate surroundings of this star over about three years. This enables a photometric and astrometric analysis of the structures in the disk. While we were unable to definitively confirm the previous claims of a massive sub-stellar object at 0.1-0.15 arcsec from the star, we found both spirals and blobs within the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star. While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings, along the primary arm of the spiral design. This blob might be due to a planet that might also be responsible for the spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected at short wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might be responsible for the emission observed in the K band. The mass of this putative planet may be constrained using photometric and dynamical arguments; it should be between 1 and 4 Jupiter masses. The brightest blobs are found at the 1:2 resonance with this putative planet
Aims. The purpose of this paper is to detect and investigate the nature of long-term radial velocity (RV) variations of K-type giants and to confirm planetary companions around the stars. Methods. We have conducted two planet search programs by precise RV measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical Observatory (OAO). The BOAO program searches for planets around 55 early K giants. The OAO program is looking for 190 G-K type giants. Results. In this paper, we report the detection of long-period RV variations of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the cause of the observed RV variations and conclude the substellar companions are most likely the cause of the RV variations. The orbital analyses yield P = 578.6 $pm$ 3.3 d, $m$ sin $i$ = 2.7 $pm$ 0.6 $M_{rm{J}}$, $a$ = 1.4 $pm$ 0.1 AU for HD 40956; P = 1056.4 $pm$ 14.3 d, $m$ sin $i$ = 4.4 $pm$ 0.4 $M_{rm{J}}$, $a$ = 2.5 $pm$ 0.1 AU for HD 111591; P = 610.2 $pm$ 3.8 d, $m$ sin $i$ = 6.3 $pm$ 1.0 $M_{rm{J}}$, $a$ = 1.6 $pm$ 0.1 AU for HD 113996.
Keck/HIRES precision radial velocities of HD 207832 indicate the presence of two Jovian-type planetary companions in Keplerian orbits around this G star. The planets have minimum masses of 0.56 and 0.73 Jupiter-masses with orbital periods of ~162 and ~1156 days, and eccentricities of 0.13 and 0.27, respectively. Stromgren b and y photometry reveals a clear stellar rotation signature of the host star with a period of 17.8 days, well separated from the period of the radial velocity variations, reinforcing their Keplerian origin. The values of the semimajor axes of the planets suggest that these objects have migrated from the region of giant planet formation to closer orbits. In order to examine the possibility of the existence of additional (small) planets in the system, we studied the orbital stability of hypothetical terrestrial-sized objects in the region between the two planets and interior to the orbit of the inner body. Results indicated that stable orbits exist only in a small region interior to planet b. However, the current observational data offer no evidence for the existence of additional objects in this system.
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