Radial Velocity Monitoring of the Young Star Hubble 4: Disentangling Starspot Lifetimes from Orbital Motion

Abstract

We studied the weak-lined T Tauri star Hubble 4, a known long-period binary, and its starspot phenomena. We used optical radial velocity (RV) data taken over a span of 14 years (2004-2010, 2017-2019) at the McDonald Observatory 2.7m Harlan J. Smith telescope and single epoch imaging from the HST/WFC3 instrument. The observed and apparent RV variations show contributions, respectively, from the binary motion as well as from a large spot group on one of the stars, presumed to be the primary. Fitting and removing the orbital signal from the RVs, we found the lower bound on the lifetime of a previously identified large spot group on the surface of the star to be at least 5.1 years. A $\sim 5$ year lower limit is a long, but not unprecedented, duration for a single spot group. The later epoch data indicate significant spot evolution has occurred, placing an upper bound on the spot group lifetime at 12 years. We find that pre-main sequence evolutionary models for the age of Taurus ($\sim 2$ Myr), combined with component mass estimates from the literature, permit us to reproduce the HST relative photometry and the binary-induced contribution to the apparent RV variations. The long-lived star spot we find on Hubble 4 has significant implications for dynamo models in young stars, as it adds evidence for long lifetimes of magnetic field topologies. There are also significant implications for young star exoplanet searches as long-lived coherent RV signals may be spot-induced and not the result of planetary motion. (This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.)

arXiv comment45 pages, 16 figures, 4 tables, to be published in the Astrophysical Journal (ApJ)

References in corpus (31)

• The chemical composition of the Sun
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• Models of Stars, Brown Dwarfs and Exoplanets
• Mapping the Shores of the Brown Dwarf Desert II: Multiple Star Formation in Taurus-Auriga
• Planet Hunters X. KIC 8462852 - Where's the Flux?
• Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra
• Zodiacal Exoplanets in Time (ZEIT) III: A short-period planet orbiting a pre-main-sequence star in the Upper Scorpius OB Association
• Connecting Flares and Transient Mass Loss Events in Magnetically Active Stars
• Hint of a transiting extended atmosphere on 55 Cancri b
• The Disk Substructures at High Angular Resolution Project (DSHARP): IV. Characterizing substructures and interactions in disks around multiple star systems
• New periodic variable stars coincident with ROSAT sources discovered using SuperWASP
• The Gould's Belt Distances Survey (GOBELINS). IV. Distance, Depth and Kinematics of the Taurus Star-Forming Region
• The Twenty-Five Year Lick Planet Search
• The Degree of Alignment Between Circumbinary Disks and Their Binary Hosts
• The quest for stellar coronal mass ejections in late-type stars: I. Investigating Balmer-line asymmetries of single stars in Virtual Observatory data
• SPECIES I: Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars
• Detection of Na, K, and H$\alpha$ absorption in the atmosphere of WASP-52b using ESPRESSO
• Starspot-induced optical and infrared radial velocity variability in T Tauri star Hubble 4
• The hot Jupiter of the magnetically-active weak-line T Tauri star V830 Tau
• Testing the Reality of Strong Magnetic Fields on T Tauri Stars: The Naked T Tauri Star Hubble 4
• Probing the Origin of Stellar Flares on M dwarfs Using TESS Data Sectors 1-3
• Time resolved spectroscopic observations of an M-dwarf flare star EV Lacertae during a flare
• How Hot is the Wind from TW Hydrae?
• On Sunspot and Starspot Lifetimes
• Star Spot Induced Radial Velocity Variability in LkCa 19
• Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES
• Evidence for abnormal H$\alpha$ variability during near-transit observations of HD 189733 b
• Dynamical Masses of Young Stars II: Young Taurus Binaries Hubble~4, FF~Tau, and HP~Tau/G3
• H-alpha Variability in PTFO8-8695 and the Possible Direct Detection of Emission from a 2 Million Year Old Evaporating Hot Jupiter

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