TY - JOUR
T1 - Rotational Modulation of Spectroscopic Zeeman Signatures in Low-mass Stars
AU - Terrien, Ryan C.
AU - Keen, Allison
AU - Oda, Katy
AU - Partsthey/them, Winter
AU - Stefánsson, Guðmundur
AU - Mahadevan, Suvrath
AU - Robertson, Paul
AU - Ninan, Joe P.
AU - Beard, Corey
AU - Bender, Chad F.
AU - Cochran, William D.
AU - Cunha, Katia
AU - Diddams, Scott A.
AU - Fredrick, Connor
AU - Halverson, Samuel
AU - Hearty, Fred
AU - Ickler, Adam
AU - Kanodia, Shubham
AU - Libby-Roberts, Jessica E.
AU - Lubin, Jack
AU - Metcalf, Andrew J.
AU - Olsen, Freja
AU - Ramsey, Lawrence W.
AU - Roy, Arpita
AU - Schwab, Christian
AU - Smith, Verne V.
AU - Turner, Ben
N1 - Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/3/1
Y1 - 2022/3/1
N2 - Accurate tracers of the stellar magnetic field and rotation are cornerstones for the study of M dwarfs and for reliable detection and characterization of their exoplanetary companions. Such measurements are particularly challenging for old, slowly rotating, fully convective M dwarfs. To explore the use of new activity and rotation tracers, we examined multiyear near-infrared (NIR) spectroscopic monitoring of two such stars-GJ 699 (Barnard's Star) and Teegarden's Star-carried out with the Habitable-zone Planet Finder spectrograph. We detected periodic variations in absorption line widths across the stellar spectrum, with higher amplitudes toward longer wavelengths. We also detected similar variations in the strength and width of the 12435.67 Å neutral potassium (K i) line, a known tracer of the photospheric magnetic field. Attributing these variations to rotational modulation, we confirm the known 145 ± 15 day rotation period of GJ 699, and measure the rotation period of Teegarden's Star to be 99.6 ± 1.4 days. Based on simulations of the K i line and the wavelength dependence of the line-width signal, we argue that the observed signals are consistent with varying photospheric magnetic fields and the associated Zeeman effect. These results highlight the value of detailed line profile measurements in the NIR for diagnosing stellar magnetic field variability. Such measurements may be pivotal for disentangling activity and exoplanet-related signals in spectroscopic monitoring of old, low-mass stars.
AB - Accurate tracers of the stellar magnetic field and rotation are cornerstones for the study of M dwarfs and for reliable detection and characterization of their exoplanetary companions. Such measurements are particularly challenging for old, slowly rotating, fully convective M dwarfs. To explore the use of new activity and rotation tracers, we examined multiyear near-infrared (NIR) spectroscopic monitoring of two such stars-GJ 699 (Barnard's Star) and Teegarden's Star-carried out with the Habitable-zone Planet Finder spectrograph. We detected periodic variations in absorption line widths across the stellar spectrum, with higher amplitudes toward longer wavelengths. We also detected similar variations in the strength and width of the 12435.67 Å neutral potassium (K i) line, a known tracer of the photospheric magnetic field. Attributing these variations to rotational modulation, we confirm the known 145 ± 15 day rotation period of GJ 699, and measure the rotation period of Teegarden's Star to be 99.6 ± 1.4 days. Based on simulations of the K i line and the wavelength dependence of the line-width signal, we argue that the observed signals are consistent with varying photospheric magnetic fields and the associated Zeeman effect. These results highlight the value of detailed line profile measurements in the NIR for diagnosing stellar magnetic field variability. Such measurements may be pivotal for disentangling activity and exoplanet-related signals in spectroscopic monitoring of old, low-mass stars.
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U2 - 10.3847/2041-8213/ac4fc8
DO - 10.3847/2041-8213/ac4fc8
M3 - Article
AN - SCOPUS:85126456051
SN - 2041-8205
VL - 927
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L11
ER -