Modification of the MOOG spectral synthesis codes to account for Zeeman broadening of spectral lines

Abstract

In an attempt to widen access to the study of magnetic fields in stellar astronomy, I present MOOGStokes, a version of the MOOG one-dimensional LTE radiative transfer code, overhauled to incorporate a Stokes vector treatment of polarized radiation through a magnetic medium. MOOGStokes is a suite of three complementary programs, which together can synthesize the disk-averaged emergent spectrum of a star with a magnetic field. The first element (a pre-processing script called CounterPoint) calculates for a given magnetic field strength, wavelength shifts and polarizations for the components of Zeeman sensitive lines. The second element (a MOOG driver called SynStokes derived from the existing MOOG driver Synth) uses the list of Zeeman shifted absorption lines together with the existing machinery of MOOG to synthesize the emergent spectrum at numerous locations across the stellar disk, accounting for stellar and magnetic field geometry. The third and final element (a post-processing script called DiskoBall) calculates the disk-averaged spectrum by weighting the individual emergent spectra by limb darkening and projected area, and applying the effects of Doppler broadening. All together, the MOOGStokes package allows users to synthesize emergent spectra of stars with magnetic fields in a familiar computational framework. MOOGStokes produces disk-averaged spectra for all Stokes vectors (I, Q, U, and V), normalized by the continuum. MOOGStokes agrees well with the predictions of INVERS10 a polarized radiative transfer code with a long history of use in the study of stellar magnetic fields. In the non-magnetic limit, MOOGStokes also agrees with the predictions of the scalar version of MOOG.

10 pages, 4 figures Accepted for publication by the Astronomical Journal. Code and tutorial available at http://www.mpia.de/~deen

References in corpus (2)

• Searching for links between magnetic fields and stellar evolution III. Measurement of magnetic fields in open cluster Ap stars with ESPaDOnS
• Stokes IQUV Magnetic Doppler Imaging of Ap stars I. ESPaDOnS and NARVAL Observations

Cited by in corpus (21)

• Zodiacal Exoplanets In Time (ZEIT) I: A Neptune-sized planet orbiting an M4.5 dwarf in the Hyades Star Cluster
• Placing the spotted T Tauri star LkCa 4 on an HR diagram
• Characterizing TW Hydra
• A high resolution spectroscopic atlas of M subdwarfs - Effective temperature and metallicity
• Doppler imaging of chemical spots on magnetic Ap/Bp stars. Numerical tests and assessment of systematic errors
• The IGRINS YSO Survey I. Stellar parameters of pre-main sequence stars in Taurus-Auriga
• Constraining atmospheric parameters and surface magnetic fields with $\text{ZeeTurbo}$: an application to SPIRou spectra
• The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars
• Estimating the atmospheric properties of 44 M dwarfs from SPIRou spectra
• Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf
• Measuring the magnetic field of young stars using iSHELL observations: BP Tau and V347 Aur
• The Mean Magnetic Field Strength of CI Tau
• Is T Tauri North a 'Classical' T Tauri star?
• The IGRINS YSO Survey III: Stellar parameters of pre-main sequence stars in Ophiuchus and Upper Scorpius
• Data-Driven Spectroscopy of Cool Stars at High Spectral Resolution
• Projected Rotational Velocities and Fundamental Properties of Low-Mass Pre-Main Sequence Stars in the Taurus-Auriga Star Forming Region
• An Interpretable Machine Learning Framework for Modeling High-Resolution Spectroscopic Data
• Star-Crossed Lovers DI Tau A and B: Orbit Characterization and Physical Properties Determination
• Using Gravity as an Age Indicator for Young Stars
• Magnetic field measurements in a sample of Class I and flat-spectrum protostars observed with SPIRou
• The Variation of Circumstellar Parameters through Early Stellar Evolution