Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCombining high contrast imaging and radial velocities to constrain the planetary architecture of nearby stars
90
0
0.0
(
0
)
Authors
A. Boehle
Ask ChatGPT about the research
No Arabic abstract
Nearby stars are prime targets for exoplanet searches and characterization using a variety of detection techniques. Combining constraints from the complementary detection methods of high contrast imaging (HCI) and radial velocity (RV) can further constrain the planetary architectures of these systems because these methods place limits at different regions of the companion mass and semi-major axis parameter space. We aim to constrain the planetary architectures from the combination of HCI and RV data for 6 nearby stars within 6 pc: $tau$ Ceti, Kapteyns star, AX Mic, 40 Eri, HD 36395, and HD 42581. We compiled the sample from stars with available archival VLT/NACO HCI data at L$^{prime}$ band (3.8 $mu$m). The NACO data were fully reanalyzed using the state-of-the-art direct imaging pipeline PynPoint and combined with RV data from HARPS, Keck/HIRES, and CORALIE. A Monte Carlo approach was used to assess the completeness in the companion mass/semi-major axis parameter space from the combination of the HCI and RV data sets. We find that the HCI data add significant information to the RV constraints, increasing the completeness for certain companions masses/semi-major axes by up to 68 - 99% for 4 of the 6 stars in our sample, and by up to 1 - 13% for the remaining stars. The improvements are strongest for intermediate semi-major axes (15 - 40 AU), corresponding to the semi-major axes of the ice giants in our own solar system. The HCI mass limits reach 5 - 20 $M_{textrm{Jup}}$ in the background-limited regime, depending on the age of the star. Through the combination of HCI and RV data, we find that stringent constraints can be placed on the possible substellar companions in these systems. Applying these methods systematically to nearby stars will quantify our current knowledge of the planet population in the solar neighborhood and inform future observations.
rate research
Read More
The G-type star GJ504A is known to host a 3 to 35 MJup companion whose temperature, mass, and projected separation all contribute to make it a test case for the planet formation theories and for atmospheric models of giant planets and light brown dwarfs. We collected data from the CHARA interferometer, SOPHIE spectrograph, and VLT/SPHERE high contrast imager to revisit the properties of the system. We measure a radius of 1.35+/- 0.04Rsun for GJ504A which yields isochronal ages of 21+/-2Myr or 4.0+/-1.8Gyr for the system and line-of-sight stellar rotation axis inclination of $162.4_{-4.3}^{+3.8}$ degrees or $18.6_{-3.8}^{+4.3}$ degrees. We re-detect the companion in the Y2, Y3, J3, H2, and K1 dual band SPHERE images. The complete 1-4 $mu$m SED shape of GJ504b is best reproduced by T8-T9.5 objects with intermediate ages ($leq1.5$Gyr), and/or unusual dusty atmospheres and/or super-solar metallicities. All six atmospheric models used yield $mathrm{T_{eff}=550 pm 50}$K for GJ504b and point toward a low surface gravity (3.5-4.0 dex). The accuracy on the metallicity value is limited by model-to-model systematics. It is not degenerate with the C/O ratio. We derive $mathrm{log:L/L_{odot}=-6.15pm0.15}$ dex for the companion compatible with masses of $mathrm{M=1.3^{+0.6}_{-0.3}M_{Jup}}$ and $mathrm{M=23^{+10}_{-9} M_{Jup}}$ for the young and old age ranges, respectively. The semi-major axis (sma) is above 27.8 au and the eccentricity lower than 0.55. The posterior on GJ~504bs orbital inclination suggests a misalignment with GJ~504A rotation axis. We combine the radial velocity and multi-epoch imaging data to exclude additional objects (90% prob.) more massive than 2.5 and 30 $mathrm{M_{Jup}}$ with sma in the range 0.01-80 au for the young and old system ages, respectively. The companion is in the envelope of the population of planets synthetized with our core-accretion model.
HD113337 is a Main-Sequence F6V field star more massive than the Sun, hosting one (possibly two) radial velocity (RV) giant planet(s) and a cold debris disk (marked by an infrared excess). We used the VEGA interferometer on the CHARA array to measure HD113337 angular diameter, and derived its linear radius using the Gaia parallax. We computed the bolometric flux to derive its effective temperature and luminosity, and we estimated its mass and age using evolutionary tracks. We used Herschel images to partially resolve the outer disk, and high-contrast images of HD113337 with the LBTI to probe the 10-80 au separation range. Finally, we combined the deduced contrast maps with previous RV of the star using the MESS2 software to bring upper mass limits on possible companions at all separations up to 80 au, taking advantage of the constraints on the age and inclination (brought by the fundamental parameter analysis and the disk imaging, respectively). We derive a limb-darkened angular diameter of 0.386 $pm$ 0.009 mas that converts into a linear radius of 1.50 $pm$ 0.04 solar radius. The fundamental parameter analysis leads to an effective temperature of 6774 $pm$ 125 K, and to two possible age solutions: one young within 14-21 Myr and one old within 0.8-1.7 Gyr. We partially resolve the known outer debris disk and model its emission. Our best solution corresponds to a radius of 85 $pm$ 20 au, an extension of 30 $pm$ 20 au and an inclination within 10-30 degrees for the outer disk. The combination of imaging contrast limits, published RV, and our new age and inclination solutions leads to a first possible estimation of the true masses of the planetary companions: $sim 7_{-2}^{+4}$ Jupiter masses for HD113337 b (confirmed companion), and $sim 16_{-3}^{+10}$ Jupiter masses for HD113337 c (candidate). We also constrain possible additional companions at larger separations.
Under certain conditions, stellar radial velocities can be determined from astrometry, without any use of spectroscopy. This enables us to identify phenomena, other than the Doppler effect, that are displacing spectral lines. The change of stellar proper motions over time (perspective acceleration) is used to determine radial velocities from accurate astrometric data, which are now available from the Gaia and Hipparcos missions. Positions and proper motions at the epoch of Hipparcos are compared with values propagated back from the epoch of the Gaia Early Data Release 3. This propagation depends on the radial velocity, which obtains its value from an optimal fit assuming uniform space motion relative to the solar system barycentre. For 930 nearby stars we obtain astrometric radial velocities with formal uncertainties better than 100 km/s; for 55 stars the uncertainty is below 10 km/s, and for seven it is below 1 km/s. Most stars that are not components of double or multiple systems show good agreement with available spectroscopic radial velocities. Astrometry offers geometric methods to determine stellar radial velocity, irrespective of complexities in stellar spectra. This enables us to segregate wavelength displacements caused by the radial motion of the stellar centre-of-mass from those induced by other effects, such as gravitational redshifts in white dwarfs.
The direct detection and characterization of planetary and substellar companions at small angular separations is a rapidly advancing field. Dedicated high-contrast imaging instruments deliver unprecedented sensitivity, enabling detailed insights into the atmospheres of young low-mass companions. In addition, improvements in data reduction and PSF subtraction algorithms are equally relevant for maximizing the scientific yield, both from new and archival data sets. We aim at developing a generic and modular data reduction pipeline for processing and analysis of high-contrast imaging data obtained with pupil-stabilized observations. The package should be scalable and robust for future implementations and in particular well suitable for the 3-5 micron wavelength range where typically (ten) thousands of frames have to be processed and an accurate subtraction of the thermal background emission is critical. PynPoint is written in Python 2.7 and applies various image processing techniques, as well as statistical tools for analyzing the data, building on open-source Python packages. The current version of PynPoint has evolved from an earlier version that was developed as a PSF subtraction tool based on PCA. The architecture of PynPoint has been redesigned with the core functionalities decoupled from the pipeline modules. Modules have been implemented for dedicated processing and analysis steps, including background subtraction, frame registration, PSF subtraction, photometric and astrometric measurements, and estimation of detection limits. The pipeline package enables end-to-end data reduction of pupil-stabilized data and supports classical dithering and coronagraphic data sets. As an example, we processed archival VLT/NACO L and M data of beta Pic b and reassessed the planets brightness and position with an MCMC analysis, and we provide a derivation of the photometric error budget.
We report precise radial velocity (RV) measurements of WASP-47, a G star that hosts three transiting planets in close proximity (a hot Jupiter, a super-Earth and a Neptune-sized planet) and a non-transiting planet at 1.4 AU. Through a joint analysis of previously published RVs and our own Keck-HIRES RVs, we significantly improve the planet mass and bulk density measurements. For the super-Earth WASP-47e ($P$ = 0.79 days), we measure a mass of 9.11 $pm$ 1.17 $M_oplus$, and a bulk density of 7.63 $pm$ 1.90 g cm$^{-3}$, consistent with a rocky composition. For the hot Jupiter WASP-47b ($P$ = 4.2 days), we measure a mass of 356 $pm$ 12 $M_oplus$ (1.12 $pm$ 0.04 $M_rm{Jup}$) and constrain its eccentricity to $<0.021$ at 3-$sigma$ confidence. For the Neptune-size planet WASP-47d ($P$ = 9.0 days), we measure a mass of 12.75 $pm$ 2.70 $M_oplus$, and a bulk density of 1.36 $pm$ 0.42 g cm$^{-3}$, suggesting it has a thick H/He envelope. For the outer non-transiting planet, we measure a minimum mass of 411 $pm$ 18 $M_oplus$ (1.29 $pm$ 0.06 $M_rm{Jup}$), an orbital period of 595.7 $pm$ 5.0 days, and an orbital eccentricity of 0.27 $pm$ 0.04. Our new measurements are consistent with but 2$-$4$times$ more precise than previous mass measurements.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
