摘要：HIP 65426 b is a recently discovered exoplanet imaged during the course of the SPHERE-SHINE survey. Here we present newL′ andM′ observations of the planet from the NACO instrument at the VLT from the NACO-ISPY survey, as well as a newY –Hspectrum andK-band photometry from SPHERE-SHINE. Using these data, we confirm the nature of the companion as a warm, dusty planet with a mid-L spectral type. From comparison of its SED with the BT-Settl atmospheric models, we derive a best-fit effective temperature ofTeff= 1618 ± 7 K, surface gravity logg= 3.78−0.03+0.04and radiusR= 1.17 ± 0.04RJ(statistical uncertainties only). Using the DUSTY and COND isochrones we estimate a mass of 8 ± 1MJ. Combining the astrometric measurements from our new datasets and from the literature, we show the first indications of orbital motion of the companion (2.6σsignificance)and derive preliminary orbital constraints. We find a highly inclined orbit (i= 1.07−10+13deg) with an orbital period of 800−400+1200yr. We also report SPHERE sparse aperture masking observations that investigate the possibility that HIP 65426 b was scattered onto its current orbit by an additional companion at a smaller orbital separation. From this data we rule out the presence of brown dwarf companions with masses greater than 16MJat separations larger than 3 AU, significantly narrowing the parameter space for such a companion.
关键词：Key wordsenstars: individual: HIP 65426planets and satellites: atmospherestechniques: high angular resolutionplanets and satellites: detectionplanetary systems
