Edasich
dK star
Number of posts : 2285
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02
 | | Subject: Results from The COPAINS Pilot Survey: 4 New Brown Dwarfs 5th May 2022, 5:31 am | |
| Results from The COPAINS Pilot Survey: four new brown dwarfs and a high companion detection rate for accelerating stars - Quote :
- The last decade of direct imaging (DI) searches for sub-stellar companions has uncovered a widely diverse sample that challenges the current formation models, while highlighting the intrinsically low occurrence rate of wide companions, especially at the lower end of the mass distribution. These results clearly show how blind surveys, crucial to constrain the underlying planet and sub-stellar companion population, are not an efficient way to increase the sample of DI companions. It is therefore becoming clear that efficient target selection methods are essential to ensure a larger number of detections. We present the results of the COPAINS Survey conducted with SPHERE/VLT, searching for sub-stellar companions to stars showing significant proper motion differences (Delta mu) between different astrometric catalogues. We observed twenty-five stars and detected ten companions, including four new brown dwarfs: HIP 21152 B, HIP 29724 B, HD 60584 B and HIP 63734 B. Our results clearly demonstrates how astrometric signatures, in the past only giving access to stellar companions, can now thanks to Gaia reveal companions well in the sub-stellar regime. We also introduce FORECAST (Finley Optimised REtrieval of Companions of Accelerating STars), a tool which allows to check the agreement between position and mass of the detected companions with the measured Delta mu. Given the agreement between the values of the masses of the new sub-stellar companions from the photometry with the model-independent ones obtained with FORECAST, the results of COPAINS represent a significant increase of the number of potential benchmarks for brown dwarf and planet formation and evolution theories.
Listed in EPE http://exoplanet.eu/catalog/hip_63734_b/http://exoplanet.eu/catalog/hip_21152_b/http://exoplanet.eu/catalog/hip_29724_b/http://exoplanet.eu/catalog/hd_60584_b/ | |
|
Edasich
dK star
Number of posts : 2285
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02
| | Subject: Re: Results from The COPAINS Pilot Survey: 4 New Brown Dwarfs 6th May 2022, 4:27 pm | |
| Fresh update!  Direct Imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS - Quote :
- We present the direct-imaging discovery of a substellar companion in orbit around a Sun-like star member of the Hyades open cluster. So far, no other substellar companions have been unambiguously confirmed via direct imaging around main-sequence stars in Hyades. The star HIP 21152 is an accelerating star as identified by the astrometry from the Gaia and Hipparcos satellites. We have detected the companion, HIP 21152 B, in multi-epoch using the high-contrast imaging from SCExAO/CHARIS and Keck/NIRC2. We have also obtained the stellar radial-velocity data from the Okayama 188cm telescope. The CHARIS spectroscopy reveals that HIP 21152 B's spectrum is consistent with the L/T transition, best fit by an early T dwarf. Our orbit modeling determines the semi-major axis and the dynamical mass of HIP 21152 B to be 17.0+7.1-3.5 au and 27.5+8.7-5.3 MJup, respectively. The mass ratio of HIP 21152 B relative to its host is ≈2%, near the planet/brown dwarf boundary suggested from recent surveys. Mass estimates inferred from luminosity evolution models are slightly higher (33-42 MJup). With a dynamical mass and a well-constrained age due to the system's Hyades membership, HIP 21152 B will become a critical benchmark in understanding the formation, evolution, and atmosphere of a substellar object as a function of mass and age. Our discovery is yet another key proof-of-concept for using precision astrometry to select direct imaging targets.
| |
|
Planet Table