scholarly journals SCExAO/CHARIS Direct Imaging of A Low-mass Companion At A Saturn-like Separation from an Accelerating Young A7 Star

2021 ◽  
Vol 162 (6) ◽  
pp. 251
Author(s):  
Jeffrey Chilcote ◽  
Taylor Tobin ◽  
Thayne Currie ◽  
Timothy D. Brandt ◽  
Tyler D. Groff ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Semimajor Axis ◽  
Velocity Data ◽  
Direct Imaging ◽  
Dynamical Mass ◽  
Low Mass ◽  
M Dwarf ◽  
Radial Velocity Data

Abstract We present the SCExAO direct imaging discovery and characterization of a low-mass companion to the nearby young A7IV star, HD 91312. SCExAO/CHARIS JHK (1.1–2.4 μm) spectra and SCExAO/HiCIAO H-band imaging identify the companion over a two year baseline in a highly inclined orbit with a maximum projected separation of 8 au. The companion, HD 91312 B, induces an 8.8σ astrometric acceleration on the star as seen with the Gaia & Hipparcos satellites and a long-term radial-velocity trend as previously identified by Borgniet et al. HD 91312 B’s spectrum is consistent with that of an early-to-mid M dwarf. Hipparcos and Gaia absolute astrometry, radial-velocity data, and SCExAO/CHARIS astrometry constrain its dynamical mass to be 0.337 − 0.044 + 0.042 M ⊙, consistent with - but far more precise than - masses derived from spectroscopy, and favors a nearly edge-on orbit with a semimajor axis of ∼9.7 au. This work is an example of precisely characterizing properties of low-mass companions at solar system-like scales from a combination of direct imaging, astrometry, and radial-velocity methods.

scholarly journals Radial velocity studies of cool stars

2014 ◽  
Vol 372 (2014) ◽  
pp. 20130088 ◽  
Author(s):  
Hugh R. A. Jones ◽  
John Barnes ◽  
Mikko Tuomi ◽  
James S. Jenkins ◽  
Guillem Anglada-Escude
Keyword(s):  
Radial Velocity ◽  
Current View ◽  
Velocity Data ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Robust Detection ◽  
Dwarf Planets ◽  
Low Mass ◽  
M Dwarf ◽  
Radial Velocity Data

Our current view of exoplanets is one derived primarily from solar-like stars with a strong focus on understanding our Solar System. Our knowledge about the properties of exoplanets around the dominant stellar population by number, the so-called low-mass stars or M dwarfs, is much more cursory. Based on radial velocity discoveries, we find that the semi-major axis distribution of M dwarf planets appears to be broadly similar to those around more massive stars and thus formation and migration processes might be similar to heavier stars. However, we find that the mass of M dwarf planets is relatively much lower than the expected mass dependency based on stellar mass and thus infer that planet formation efficiency around low-mass stars is relatively impaired. We consider techniques to overcome the practical issue of obtaining good quality radial velocity data for M dwarfs despite their faintness and sustained activity and emphasize (i) the wavelength sensitivity of radial velocity signals, (ii) the combination of radial velocity data from different experiments for robust detection of small amplitude signals, and (iii) the selection of targets and radial velocity interpretation of late-type M dwarfs should consider H α behaviour.

scholarly journals An ultra-short period rocky super-Earth orbiting the G2-star HD 80653

2020 ◽  
Vol 633 ◽  
pp. A133 ◽  
Author(s):  
G. Frustagli ◽  
E. Poretti ◽  
T. Milbourne ◽  
L. Malavolta ◽  
A. Mortier ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Thermal Emission ◽  
Earth Planet ◽  
Period Orbit ◽  
Short Period ◽  
Orbital Phase ◽  
Solar Type ◽  
Radial Velocity Data

Ultra-short period (USP) planets are a class of exoplanets with periods shorter than one day. The origin of this sub-population of planets is still unclear, with different formation scenarios highly dependent on the composition of the USP planets. A better understanding of this class of exoplanets will, therefore, require an increase in the sample of such planets that have accurate and precise masses and radii, which also includes estimates of the level of irradiation and information about possible companions. Here we report a detailed characterization of a USP planet around the solar-type star HD 80653 ≡EP 251279430 using the K2 light curve and 108 precise radial velocities obtained with the HARPS-N spectrograph, installed on the Telescopio Nazionale Galileo. From the K2 C16 data, we found one super-Earth planet (Rb = 1.613 ± 0.071 R⊕) transiting the star on a short-period orbit (Pb = 0.719573 ± 0.000021 d). From our radial velocity measurements, we constrained the mass of HD 80653 b to Mb = 5.60 ± 0.43 M⊕. We also detected a clear long-term trend in the radial velocity data. We derived the fundamental stellar parameters and determined a radius of R⋆ = 1.22 ± 0.01 R⊙ and mass of M⋆ = 1.18 ± 0.04 M⊙, suggesting that HD 80653 has an age of 2.7 ± 1.2 Gyr. The bulk density (ρb = 7.4 ± 1.1 g cm−3) of the planet is consistent with an Earth-like composition of rock and iron with no thick atmosphere. Our analysis of the K2 photometry also suggests hints of a shallow secondary eclipse with a depth of 8.1 ± 3.7 ppm. Flux variations along the orbital phase are consistent with zero. The most important contribution might come from the day-side thermal emission from the surface of the planet at T ~ 3480 K.

scholarly journals The potential for imaging low-mass companions to solar-type stars: Utilising radial-velocity data from the AAPS, Keck & Lick projects

2005 ◽  
Vol 1 (C200) ◽  
pp. 593-596
Author(s):  
J. S. Jenkins ◽  
H. R. A. Jones ◽  
C. G. Tinney ◽  
C. McCarthy ◽  
B. D. Carter ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Velocity Data ◽  
Solar Type ◽  
Low Mass ◽  
Radial Velocity Data

scholarly journals Kinematics of Disk Stars in the Solar Neighbourhood

1998 ◽  
Vol 11 (1) ◽  
pp. 574-574
Author(s):  
A.E. Gómez ◽  
S. Grenier ◽  
S. Udry ◽  
M. Haywood ◽  
V. Sabas ◽  
...  
Keyword(s):  
Dispersion Relation ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Tangential Velocity ◽  
Thin Disk ◽  
The Other ◽  
Proper Motions ◽  
Velocity Data ◽  
Kinematic Data ◽  
Radial Velocity Data

Using Hipparcos parallaxes and proper motions together with radial velocity data and individual ages estimated from isochones, the velocity ellipsoid has been determined as a function of age. On the basis of the available kinematic data two different samples were considered: a first one (7789 stars) for which only tangential velocities were calculated and a second one containing 3104 stars with available U, V and W velocity components and total velocities ≤ 65 km.s-1. The main conclusions are: -Mixing is not complete at about 0.8-1 Gyr. -The shape of the velocity ellipsoid changes with time getting rounder from σu/σv/σ-w = 1/0.63/0.42 ± 0.04 at about 1 Gyr to1/0.7/0.62 ±0.04 at 4-5 Gyr. -The age-velocity-dispersion relation (from the sample with kinematical selection) rises to a maximum, thereafter remaining roughly constant; there is no dynamically significant evolution of the disk after about 4-5 Gyr. -Among the stars with solar metallicities and log(age) > 9.8 two groups are identified: one has typical thin disk characteristics, the other is older than 10 Gyr and lags the LSR at about 40 km.s-1 . -The variation of the tangential velocity with age(without selection on the tangential velocity) shows a discontinuity at about 10 Gyr, which may be attributed to stars typically of the thick disk populations for ages > 10 Gyr.

An Efficient Dual-Resolution Approach for Ensemble Data Assimilation and Tests with Simulated Doppler Radar Data

2008 ◽  
Vol 136 (3) ◽  
pp. 945-963 ◽  
Author(s):  
Jidong Gao ◽  
Ming Xue
Keyword(s):  
High Resolution ◽  
Data Assimilation ◽  
Radial Velocity ◽  
Computational Cost ◽  
Radar Data ◽  
Horizontal Resolution ◽  
Velocity Data ◽  
Background Error ◽  
Cross Covariance ◽  
Radial Velocity Data

Abstract A new efficient dual-resolution (DR) data assimilation algorithm is developed based on the ensemble Kalman filter (EnKF) method and tested using simulated radar radial velocity data for a supercell storm. Radar observations are assimilated on both high-resolution and lower-resolution grids using the EnKF algorithm with flow-dependent background error covariances estimated from the lower-resolution ensemble. It is shown that the flow-dependent and dynamically evolved background error covariances thus estimated are effective in producing quality analyses on the high-resolution grid. The DR method has the advantage of being able to significantly reduce the computational cost of the EnKF analysis. In the system, the lower-resolution ensemble provides the flow-dependent background error covariance, while the single-high-resolution forecast and analysis provides the benefit of higher resolution, which is important for resolving the internal structures of thunderstorms. The relative smoothness of the covariance obtained from the lower 4-km-resolution ensemble does not appear to significantly degrade the quality of analysis. This is because the cross covariance among different variables is of first-order importance for “retrieving” unobserved variables from the radar radial velocity data. For the DR analysis, an ensemble size of 40 appears to be a reasonable choice with the use of a 4-km horizontal resolution in the ensemble and a 1-km resolution in the high-resolution analysis. Several sensitivity tests show that the DR EnKF system is quite robust to different observation errors. A 4-km thinned data resolution is a compromise that is acceptable under the constraint of real-time applications. A data density of 8 km leads to a significant degradation in the analysis.

scholarly journals Precipitation cloud identification based on faster-RCNN for Doppler weather radar

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Yuanbo Ran ◽  
Haijiang Wang ◽  
Li Tian ◽  
Jiang Wu ◽  
Xiaohong Li
Keyword(s):  
Radial Velocity ◽  
Vertical Direction ◽  
Weather Radar ◽  
Radar Reflectivity ◽  
Convective Precipitation ◽  
Horizontal Wind ◽  
Doppler Weather Radar ◽  
Velocity Data ◽  
Precipitation Processes ◽  
Radial Velocity Data

AbstractPrecipitation clouds are visible aggregates of hydrometeor in the air that floating in the atmosphere after condensation, which can be divided into stratiform cloud and convective cloud. Different precipitation clouds often accompany different precipitation processes. Accurate identification of precipitation clouds is significant for the prediction of severe precipitation processes. Traditional identification methods mostly depend on the differences of radar reflectivity distribution morphology between stratiform and convective precipitation clouds in three-dimensional space. However, all of them have a common shortcoming that the radial velocity data detected by Doppler Weather Radar has not been applied to the identification of precipitation clouds because it is insensitive to the convective movement in the vertical direction. This paper proposes a new method for precipitation clouds identification based on deep learning algorithm, which is according the distribution morphology of multiple radar data. It mainly includes three parts, which are Constant Altitude Plan Position Indicator data (CAPPI) interpolation for radar reflectivity, Radial projection of the ground horizontal wind field by using radial velocity data, and the precipitation clouds identification based on Faster-RCNN. The testing result shows that the method proposed in this paper performs better than the traditional methods in terms of precision. Moreover, this method boasts great advantages in running time and adaptive ability.

scholarly journals Red Optical Planet Survey: A radial velocity search for low mass M dwarf planets

2013 ◽  
Vol 47 ◽  
pp. 05002
Author(s):  
J.R. Barnes ◽  
J.S. Jenkins ◽  
H.R.A. Jones ◽  
P. Rojo ◽  
P. Arriagada ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Dwarf Planets ◽  
Low Mass ◽  
M Dwarf

The CORAVEL Radial Velocity Data Base

2017 ◽  
Vol 13 (S334) ◽  
pp. 271-272
Author(s):  
Stéphane Udry ◽  
Maxime Marmier ◽  
Michel Mayor ◽  
Johannes Andersen ◽  
Birgitta Nordström
Keyword(s):  
Radial Velocity ◽  
Data Base ◽  
Radial Velocities ◽  
Velocity Data ◽  
Radial Velocity Data

AbstractFrom 1977 to 1999, thousands of accurate radial velocities in both hemispheres were made on a large variety of programmes with the two CORAVEL scanners. The data base of ~350000 individual observations will now be made available to complement the Gaia data.

scholarly journals A microvariability study of nearby M dwarfs from the Western Italian Alps: Status update

2010 ◽  
Vol 6 (S276) ◽  
pp. 525-526
Author(s):  
Mario Damasso ◽  
Andrea Bernagozzi ◽  
Enzo Bertolini ◽  
Paolo Calcidese ◽  
Paolo Giacobbe ◽  
...  
Keyword(s):  
Italian Alps ◽  
M Dwarfs ◽  
Red Dwarfs ◽  
Typical Period ◽  
Low Mass ◽  
M Stars ◽  
Rocky Planets ◽  
Long Term Survey

AbstractSmall ground-based telescopes can effectively be used to look for transiting rocky planets around nearby low-mass M stars, as recently demonstrated for example by the MEarth project. Since December 2009 at the Astronomical Observatory of the Autonomous Region of Aosta Valley (OAVdA) we are monitoring photometrically a sample of red dwarfs with accurate parallax measurements. The primary goal of this ‘pilot study’ is the characterization of the photometric microvariability of each target over a typical period of approximately 2 months. This is the preparatory step to long-term survey with an array of identical small telescopes, with kick-off in early 2011. Here we discuss the present status of the study, describing the stellar sample, and presenting the most interesting results obtained so far, including the aggressive data analysis devoted to the characterization of the variability properties of the sample and the search for transit-like signals.

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