اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA Planetary System Around HD 155358: The Lowest Metallicity Planet Host Star
126
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report the detection of two planetary mass companions to the solar-type star HD 155358. The two planets have orbital periods of 195.0 and 530.3 days, with eccentricities of 0.11 and 0.18. The minimum masses for these planets are 0.89 and 0.50 Jupiter masses respectively. The orbits are close enough to each other, and the planets are sufficiently massive, that the planets are gravitationally interacting with each other, with their eccentricities and arguments of periastron varying with periods of 2300--2700 years. While large uncertainties remain in the orbital eccentricities, our orbital integration calculations indicate that our derived orbits would be dynamically stable for at least 10^8 years. With a metallicity [Fe/H] of -0.68, HD 155358 is tied with the K1III giant planet host star HD 47536 for the lowest metallicity of any planet host star yet found. Thus, a star with only 21% of the heavy-element content of our Sun was still able to form a system of at least two Jovian-mass planets and have their orbits evolve to semi-major axes of 0.6-1.2 AU.
قيم البحث
اقرأ أيضاً
We report the detection of a double planetary system orbiting around the evolved intermediate-mass star HD 4732 from precise Doppler measurements at Okayama Astrophysical Observatory (OAO) and Anglo-Australian Observatory (AAO). The star is a K0 subg
iant with a mass of 1.7 M_sun and solar metallicity. The planetary system is composed of two giant planets with minimum mass of msini=2.4 M_J, orbital period of 360.2 d and 2732 d, and eccentricity of 0.13 and 0.23, respectively. Based on dynamical stability analysis for the system, we set the upper limit on the mass of the planets to be about 28 M_J (i>5 deg) in the case of coplanar prograde configuration.
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 eccentricit
y 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.
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.
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 interact
ions. 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.
Extra-solar planet search programs require high-precision velocity measurements. They need to study how to disentangle radial-velocity variations due to Doppler motion from the noise induced by stellar activity. We monitored the active K2V star HD 18
9733 and its transiting planetary companion that has a 2.2-day orbital period. We used the high-resolution spectograph SOPHIE mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to obtain 55 spectra of HD 189733 over nearly two months. We refined the HD 189733b orbit parameters and put limits on the eccentricity and on a long-term velocity gradient. After subtracting the orbital motion of the planet, we compared the variability of spectroscopic activity indices to the evolution of the radial-velocity residuals and the shape of spectral lines. The radial velocity, the spectral-line profile and the activity indices measured in HeI (5875.62 AA), Halpha (6562.81 AA) and the CaII H&K lines (3968.47 AA and 3933.66 AA, respectively) show a periodicity around the stellar rotation period and the correlations between them are consistent with a spotted stellar surface in rotation. We used such correlations to correct for the radial-velocity jitter due to stellar activity. This results in achieving high precision on the orbit parameters, with a semi-amplitude K = 200.56 pm 0.88 m.s-1 and a derived planet mass of M_{P}=1.13 pm 0.03 M$_{Jup}$.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
