اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدOrbital and Evolutionary Constraints on the Planet Hosting Binary GJ 86 from the Hubble Space Telescope
141
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
This paper presents new observations of the planet-hosting, visual binary GJ 86 (HR 637) using the Hubble Space Telescope. Ultraviolet and optical imaging with WFC3 confirms the stellar companion is a degenerate star and indicates the binary semimajor axis is larger than previous estimates, with a > 28 AU. Optical STIS spectroscopy of the secondary reveals a helium-rich white dwarf with C2 absorption bands and Teff = 8180 K, thus making the binary system rather similar to Procyon. Based on the 10.8 pc distance, the companion has 0.59 Msun and descended from a main-sequence A star of 1.9 Msun with an original orbital separation a > 14 AU. If the giant planet is coplanar with the binary, the mass of GJ 86Ab is between 4.4 and 4.7 MJup. The similarity of GJ 86 and Procyon prompted a re-analysis of the white dwarf in the latter system, with the tentative conclusion that Procyon hosts a planetesimal population. The periastron distance in Procyon is 20% smaller than in alpha Cen AB, but the metal-enriched atmosphere of Procyon B indicates that the planet formation process minimally attained 25 km bodies, if not small planets as in alpha Cen.
قيم البحث
اقرأ أيضاً
We used HST/WFC3 observations of a sample of 26 nearby ($le$20 pc) mid to late T dwarfs to search for cooler companions and measure the multiplicity statistics of brown dwarfs. Tightly-separated companions were searched for using a double-PSF fitting
algorithm. We also compared our detection limits based on simulations to other prior T5+ brown dwarf binary programs. No new wide or tight companions were identified, which is consistent with the number of known T5+ binary systems and the resolution limits of WFC3. We use our results to add new constraints to the binary fraction of T-type brown dwarfs. Modeling selection effects and adopting previously derived separation and mass ratio distributions, we find an upper limit total binary fraction of <16% and <25% assuming power law and flat mass ratio distributions respectively, which are consistent with previous results. We also characterize a handful of targets around the L/T transition.
Located at ~2pc, the L7.5+T0.5 dwarfs system WISE J104915.57-531906.1 (Luhman16AB) is the third closest system known to Earth, making it a key benchmark for detailed investigation of brown dwarf atmospheric properties, thermal evolution, multiplicity
, and planet-hosting frequency. In the first study of this series -- based on a multi-cycle Hubble Space Telescope (HST) program -- we provide an overview of the project and present improved estimates of positions, proper motions, annual parallax, mass ratio, and the current best assessment of the orbital parameters of the A-B pair. Our HST observations encompass the apparent periastron of the binary at 220.5+/-0.2 mas at epoch 2016.402. Although our data seem to be inconsistent with recent ground-based astrometric measurements, we also exclude the presence of third bodies down to Neptune masses and periods longer than a year.
The coronagraphic instrument currently proposed for the WFIRST-AFTA mission will be the first example of a space-based coronagraph optimized for extremely high contrasts that are required for the direct imaging of exoplanets reflecting the light of t
heir host star. While the design of this instrument is still in progress, this early stage of development is a particularly beneficial time to consider the operation of such an instrument. In this paper, we review current or planned operations on the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST) with a focus on which operational aspects will have relevance to the planned WFIRST-AFTA coronagraphic instrument. We identify five key aspects of operations that will require attention: 1) detector health and evolution, 2) wavefront control, 3) observing strategies/post-processing, 4) astrometric precision/target acquisition, and 5) polarimetry. We make suggestions on a path forward for each of these items.
We report on an ultraviolet spectroscopic survey of red giants observed by the Hubble Space Telescope, focusing on spectra of the Mg II h & k lines near 2800 A in order to study stellar chromospheric emission, winds, and astrospheric absorption. We f
ocus on spectral types between K2 III and M5 III, a spectral type range with stars that are noncoronal, but possessing strong, chromospheric winds. We find a very tight relation between Mg II surface flux and photospheric temperature, supporting the notion that all K2-M5 III stars are emitting at a basal flux level. Wind velocities (V_w) are generally found to decrease with spectral type, with V_w decreasing from ~40 km/s at K2 III to ~20 km/s at M5 III. We find two new detections of astrospheric absorption, for Sigma Pup (K5 III) and Gamma Eri (M1 III). This absorption signature had previously only been detected for Alpha Tau (K5 III). For the three astrospheric detections the temperature of the wind after the termination shock correlates with V_w, but is lower than predicted by the Rankine-Hugoniot shock jump conditions, consistent with the idea that red giant termination shocks are radiative shocks rather than simple hydrodynamic shocks. A full hydrodynamic simulation of the Gamma Eri astrosphere is provided to explore this further.
(Abridged) Hubble Space Telescope (HST) Fine Guidance Sensor astrometric observations of the G4 IV star HD 38529 are combined with the results of the analysis of extensive ground-based radial velocity data to determine the mass of the outermost of tw
o previously known companions. Our new radial velocities obtained with the Hobby-Eberly Telescope and velocities from the Carnegie-California group now span over eleven years. With these data we obtain improved RV orbital elements for both the inner companion, HD 38529 b and the outer companion, HD 38529 c. We identify a rotational period of HD 38529 (P_{rot}=31.65 +/- 0.17 d) with FGS photometry. We model the combined astrometric and RV measurements to obtain the parallax, proper motion, perturbation period, perturbation inclination, and perturbation size due to HD 38529 c. For HD 38529 c we find P = 2136.1 +/- 0.3 d, perturbation semi-major axis alpha =1.05 +/-0.06$ mas, and inclination $i$ = 48.3 deg +/- 4 deg. Assuming a primary mass M_* = 1.48 M_{sun}, we obtain a companion mass M_c = 17.6 ^{+1.5}_{-1.2} M_{Jup}, 3-sigma above a 13 M_{Jup} deuterium burning, brown dwarf lower limit. Dynamical simulations incorporating this accurate mass for HD 38529 c indicate that a near-Saturn mass planet could exist between the two known companions. We find weak evidence of an additional low amplitude signal that can be modeled as a planetary-mass (~0.17 M$_{Jup}) companion at P~194 days. Additional observations (radial velocities and/or Gaia astrometry) are required to validate an interpretation of HD 38529 d as a planetary-mass companion. If confirmed, the resulting HD 38529 planetary system may be an example of a Packed Planetary System.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
