A Data-Driven Technique for Measuring Stellar Rotation

Abstract

Measuring stellar rotational velocities is a powerful way to probe the many astrophysical phenomena that drive, or are driven by, the evolution of stellar angular momentum. In this paper, we present a novel data-driven approach to measuring the projected rotational velocity, $v\sin i$. Rather than directly measuring the broadening of spectral lines, we leverage the large information content of high-resolution spectral data to empirically estimate $v\sin i$. We adapt the framework laid down by The Cannon (Ness et al. 2015), which trains a generative model of the stellar flux as a function of wavelength using high-fidelity reference data, and can then produce estimates of stellar parameters and abundances for other stars directly from their spectra. Instead of modeling the flux as a function of wavelength, however, we model the first derivative of the spectra, as we expect the slopes of spectral lines to change as a function of $v\sin i$. This technique is computationally efficient and provides a means of rapidly estimating $v\sin i$ for large numbers of stars in spectroscopic survey data. We analyze SDSS APOGEE spectra, constructing a model informed by high-fidelity stellar parameter estimates derived from high-resolution California Kepler Survey spectra of the same stars. We use the model to estimate $v\sin i$ up to $15km{s}^{-1}$ for $27,000$ APOGEE spectra, in fractions of a second per spectrum. Our estimates agree with the APOGEE $v\sin i$ estimates to within $1.2km{s}^{-1}$.

26 pages, 10 figures. Accepted for publication in ApJ

References in corpus (27)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The SIMBAD astronomical database
• ASPCAP: The Apogee Stellar Parameter and Chemical Abundances Pipeline
• Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
• The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
• Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments
• The Data Reduction Pipeline for the Apache Point Observatory Galactic Evolution Experiment
• The Cannon: A data-driven approach to stellar label determination
• Rotation and differential rotation of active Kepler stars
• The California-Kepler Survey. I. High Resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets
• On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey
• Stellar Rotation Periods of the Kepler Objects of Interest: A Dearth of Close-in Planets around Fast Rotators
• A catalogue of rotation and activity in early-M stars
• Rotation Velocities for M-dwarfs
• Rotation Periods, Variability Properties and Ages for Kepler Exoplanet Candidate Host Stars
• The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
• Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum
• The Impact of Stellar Rotation on the Detectability of Habitable Planets Around M Dwarfs
• Observational studies of stellar rotation
• The Cannon 2: A data-driven model of stellar spectra for detailed chemical abundance analyses
• Fundamental M-dwarf parameters from high-resolution spectra using PHOENIX ACES models: I. Parameter accuracy and benchmark stars
• The SDSS-III APOGEE Radial Velocity Survey of M dwarfs I: Description of Survey and Science Goals
• The Rotation-Activity Correlations in K and M dwarfs. II. New constraints on the dynamo mechanisms in late-K and M dwarfs before and at the transition to complete convection
• Photospheric properties and fundamental parameters of M dwarfs
• Dynamics of rotation in M dwarfs: Indications for a change in the dynamo regime in stars at the onset of complete convection
• The Rotation of M Dwarfs Observed by the Apache Point Galactic Evolution Experiment
• A Near-Infrared Spectroscopic Survey at the SDSS 2.5-meter Telescope?

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