SCExAO/CHARIS and Gaia Direct Imaging and Astrometric Discovery of a Superjovian Planet 3–4 λ / D from the Accelerating Star HIP 54515*

2025/12/01 by Thayne Currie, Currie, Thayne, Yiting Li +65 · 3 voices · 5 citations
Physics and Astronomy · #Astrometry #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Coronagraph #Direct imaging #Eccentricity (behavior) #Exoplanet #Luminosity #Orbital eccentricity #Planet #Stellar, planetary, and galactic studies #Telescope

paper · pdf · open access · doi:10.3847/1538-3881/ae1a82

published in The Astronomical Journal 171(1), 5 (Institute of Physics)

openalex created_date 2025/12/03 · openalex publication_date 2025/12/03 · openalex updated_date 2026/08/04

Abstract

Abstract We present the discovery of a superjovian planet around the young A5 star HIP 54515, detected using precision astrometry from the Hipparcos Gaia Catalogue of Accelerations and high-contrast imaging with SCExAO/CHARIS from the recently commenced OASIS program. SCExAO/CHARIS detects HIP 54515 b in five epochs 0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 145–0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 192 from the star (∼3–4 λ / D at 1.65 μ m), exhibiting clockwise orbital motion. HIP 54515 b lies near the M/L transition with a luminosity of log( L / L ⊙ ) ∼−3.52 ± 0.03. Dynamical modeling constrains its mass and mass ratio to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>17.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>7.6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M Jup and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.0090</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.0024</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.0036</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and favors a ∼25 au semimajor axis. HIP 54515 b adds to a growing list of superjovian planets with moderate eccentricities ( e ≈ 0.4). Now, the third planet discovered from surveys combining high-contrast extreme adaptive optics imaging with precision astrometry, HIP 54515 b, should help improve empirical constraints on the luminosity evolution and eccentricity distribution of the most massive planets. It may also provide a key technical test of the Roman Space Telescope Coronagraph Instrument’s performance in the low stellar flux, small angular separation limit, and a demonstration of its ability to yield constrainable planet spectral properties.

Citations

• A New Algorithm for Point‐Spread Function Subtraction in High‐Contrast Imaging: A Demonstration with Angular Differential Imaging
• Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique
• emcee: The MCMC Hammer
• A New Distortion Solution for NIRC2 on the Keck II Telescope
• OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B: A Substellar Companion Suitable for the Roman Coronagraph Technology Demonstration*
• On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb
• VLTI/GRAVITY Observations of AF Lep b: Preference for Circular Orbits, Cloudy Atmospheres, and a Moderately Enhanced Metallicity
• The California Legacy Survey. I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades
• INTRINSIC COLORS, TEMPERATURES, AND BOLOMETRIC CORRECTIONS OF PRE-MAIN-SEQUENCE STARS

Cited by

• OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B: A Substellar Companion Suitable for the Roman Coronagraph Technology Demonstration*
• Decisively Demonstrating Roman CGI's TTR5 Requirement by Reimaging a Newly-Discovered Brown Dwarf Orbiting a Bright Accelerating Star
• The HIP 54515 b Superjovian Planet as an Early, Critical Look at the Roman Coronagraph's Performance in the Faint Target Star, Small IWA Limit
• A Test of Substellar Evolutionary Models with High-Precision Ages from Asteroseismology and Gyrochronology for the Benchmark System HR 7672AB
• Discovery of a Low-Mass Companion to the Accelerating Star HIP 53005 with Strongly Conflicting Mass Estimates

Discussions

• (announcement 1 of 2) everyone, say hello to ... HIP 54515 b: the 3rd planet jointly discovered from direct imaging and astrometry arxiv.org/abs/2512.02159 [Currie & Li et al. 2025, AJ in press] Press [bsky, 24 points, 1 comments]
• From SCExAO and CHARIS: Currie+ with a superJovian around HIP 54515 and El Morsy+ with substellar companion HIP 71618 adding to the superJovian/Brown Dwarf menagerie at 17 and 60 Jupiter masses respec [bsky, 16 points, 0 comments]
• SCExAO/CHARIS and Gaia Imaging and Astrometric Discovery of a Superjovian Planet from the Accelerating Star HIP 54515 / OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B - A Substel [bsky, 1 points, 0 comments]

Related

• The HIP 54515 b Superjovian Planet as an Early, Critical Look at the Roman Coronagraph's Performance in the Faint Target Star, Small IWA Limit
• A New Type of Exoplanet Direct Imaging Search: The SCExAO/CHARIS Survey of Accelerating Stars
• OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B: A Substellar Companion Suitable for the Roman Coronagraph Technology Demonstration*
• Multi-band Spectral and Astrometric Characterization of the HIP 99770 b Planet with SCExAO/CHARIS and Gaia
• A Jupiter analogue and a cold Super-Neptune orbiting the solar-twin star HIP 104045