اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA High-Eccentricity Low-Mass Companion to HD 89744
48
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
HD 89744 is an F7 V star with mass 1.4 M, effective temperature 6166 K, age 2.0 Gy and metallicity [Fe/H]= 0.18. The radial velocity of the star has been monitored with the AFOE spectrograph at the Whipple Observatory since 1996, and evidence has been found for a low mass companion. The data were complemented by additional data from the Hamilton spectrograph at Lick Observatory during the companions periastron passage in fall 1999. As a result, we have determined the stars orbital wobble to have period P = 256 d, orbital amplitude K = 257 m/s, and eccentricity e = 0.7. From the stellar mass we infer that the companion has minimum mass m2 sin i = 7.2 MJup in an orbit with semi-major axis a2 = 0.88 AU. The eccentricity of the orbit, among the highest known for extra-solar planets, continues the trend that extra-solar planets with semi-major axes greater than about 0.15 AU tend to have much higher eccentricities than are found in our solar system. The high metallicity of the parent star reinforces the trend that parent stars of extra-solar planets tend to have high metallicity
قيم البحث
اقرأ أيضاً
We report the discovery of a low-mass companion to the nearby (d = 47 pc) F7V star HD 984. The companion is detected 0.19 away from its host star in the L band with the Apodizing Phase Plate on NaCo/VLT and was recovered by L-band non-coronagraphic i
maging data taken a few days later. We confirm the companion is co-moving with the star with SINFONI integral field spectrograph H+K data. We present the first published data obtained with SINFONI in pupil-tracking mode. HD 984 has been argued to be a kinematic member of the 30 Myr-old Columba group, and its HR diagram position is not altogether inconsistent with being a ZAMS star of this age. By consolidating different age indicators, including isochronal age, coronal X-ray emission, and stellar rotation, we independently estimate a main sequence age of 115$pm$85 Myr (95% CL) which does not rely on this kinematic association. The mass of directly imaged companions are usually inferred from theoretical evolutionary tracks, which are highly dependent on the age of the star. Based on the age extrema, we demonstrate that with our photometric data alone, the companions mass is highly uncertain: between 33 and 96 M$_{rm Jup}$ (0.03-0.09 M$_{odot}$) using the COND evolutionary models. We compare the companions SINFONI spectrum with field dwarf spectra to break this degeneracy. Based on the slope and shape of the spectrum in the H-band, we conclude that the companion is an M$6.0pm0.5$ dwarf. The age of the system is not further constrained by the companion, as M dwarfs are poorly fit on low-mass evolutionary tracks. This discovery emphasizes the importance of obtaining a spectrum to spectral type companions around F-stars.
The circumstellar disk of the Herbig Fe star HD 142527 is host to several remarkable features including a warped inner disk, a 120 au-wide annular gap, a prominent dust trap and several spiral arms. A low-mass companion, HD 142527 B, was also found o
rbiting the primary star at $sim$14 au. This study aims to better characterize this companion, which could help explain its impact on the peculiar geometry of the disk. We observed the source with VLT/SINFONI in $H$+$K$ band in pupil-tracking mode. Data were post-processed with several algorithms based on angular differential imaging (ADI). HD 142527 B is conspicuously re-detected in most spectral channels, which enables us to extract the first medium-resolution spectrum of a low-mass companion within 0.1 from its central star. Fitting our spectrum with both template and synthetic spectra suggests that the companion is a young M2.5$pm$1.0 star with an effective temperature of $3500pm100$ K, possibly surrounded with a hot (1700 K) circum-secondary environment. Pre-main sequence evolutionary tracks provide a mass estimate of $0.34pm0.06 M_{odot}$, independent of the presence of a hot environment. However, the estimated stellar radius and age do depend on that assumption; we find a radius of $1.37 pm 0.05 R_{odot}$ (resp. $1.96 pm 0.10 R_{odot}$) and an age of $1.8^{+1.2}_{-0.5}$ Myr (resp. $0.75 pm 0.25$ Myr) in the case of the presence (resp. absence) of a hot environment contributing in $H$+$K$. Our new values for the mass and radius yield a mass accretion rate of $sim$5 $times 10^{-9} M_{odot}$ yr$^{-1}$ (2-3% that of the primary). Our results illustrate thus the potential for SINFONI+ADI to characterize faint close-in companions. The new spectral type makes HD 142527 B a twin of the well known TW Hya T-Tauri star, and the revision of its mass to higher values further supports its role in shaping the disk.
We report the discovery of a substellar-mass companion to the K0-giant HD 17092 with the Hobby-Eberly Telescope. In the absence of any correlation of the observed 360-day periodicity with the standard indicators of stellar activity, the observed radi
al velocity variations are most plausibly explained in terms of a Keplerian motion of a planetary-mass body around the star. With the estimated stellar mass of 2.3Msun, the minimum mass of the planet is 4.6MJ. The planets orbit is characterized by a mild eccentricity of e=0.17 and a semi-major axis of 1.3 AU. This is the tenth published detection of a planetary companion around a red giant star. Such discoveries add to our understanding of planet formation around intermediate-mass stars and they provide dynamical information on the evolution of planetary systems around post-main sequence stars.
With the uniquely high contrast within 0.1 (Delta mag(L) = 5-6.5 magnitudes) available using Sparse Aperture Masking (SAM) with NACO at VLT, we detected asymmetry in the flux from the Herbig Fe star HD 142527 with a barycenter emission situated at a
projected separation of 88+/-5 mas (12.8+/-1.5 AU at 145 pc) and flux ratios in H, K, and L of 0.016+/-0.007, 0.012+/-0.008, 0.0086+/-0.0011 respectively (3-sigma errors) relative to the primary star and disk. After extensive closure-phase modeling, we interpret this detection as a close-in, low-mass stellar companion with an estimated mass of ~0.1-0.4 M_Sun. HD 142527 has a complex disk structure, with an inner gap imaged in both the near and mid-IR as well as a spiral feature in the outer disk in the near-IR. This newly detected low-mass stellar companion may provide a critical explanation of the observed disk structure.
We present the discovery of a planetary-mass companion to CFHTWIR-Oph 98, a low-mass brown dwarf member of the young Ophiuchus star-forming region, with a wide 200-au separation (1.46 arcsec). The companion was identified using Hubble Space Telescope
images, and confirmed to share common proper motion with the primary using archival and new ground-based observations. Based on the very low probability of the components being unrelated Ophiuchus members, we conclude that Oph 98 AB forms a binary system. From our multi-band photometry, we constrain the primary to be an M9-L1 dwarf, and the faint companion to have an L2-L6 spectral type. For a median age of 3 Myr for Ophiuchus, fits of evolutionary models to measured luminosities yield masses of $15.4pm0.8$ M$_mathrm{Jup}$ for Oph 98 A and $7.8pm0.8$ M$_mathrm{Jup}$ for Oph 98 B, with respective effective temperatures of $2320pm40$ K and $1800pm40$ K. For possible system ages of 1-7 Myr, masses could range from 9.6-18.4 M$_mathrm{Jup}$ for the primary, and from 4.1-11.6 M$_mathrm{Jup}$ for the secondary. The low component masses and very large separation make this binary the lowest binding energy system imaged to date, indicating that the outcome of low-mass star formation can result in such extreme, weakly-bound systems. With such a young age, Oph 98 AB extends the growing population of young free-floating planetary-mass objects, offering a new benchmark to refine formation theories at the lowest masses.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
