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 - Funding Information:
We acknowledge support from NSF grant Nos. AST 1006676, AST 1126413, AST 1310875, AST 1310885, AST 2009955, AST 2009889, AST 2009982, AST 2009554, and the NASA Astrobiology Institute (NNA09DA76A) in our pursuit of precision radial velocities in the NIR. We also acknowledge support from the Heising-Simons Foundation via grant No. 2017-0494. This research was conducted in part under NSF grant Nos. AST-2108493, AST-2108512, AST-2108569, and AST-2108801 in support of the HPF Guaranteed Time Observations survey. We also acknowledge support from the NASA Extreme Precision Radial Velocity program via grant No. 80NSSC21K2006. We also acknowledge support from the Carleton College Towsley Endowment, as well as the Minnesota Space Grant Consortium. K.C. and V.S. acknowledge partial support by the National Science Foundation through NSF grant No. AST-2009507.
Funding Information:
These results are based on observations obtained with the Habitable-zone Planet Finder Spectrograph on the Hobby–Eberly Telescope (HET). The HET is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universitat Munchen, and Georg-August Universitat Gottingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. The HET collaboration acknowledges the support and resources from the Texas Advanced Computing Center. We thank the resident astronomers and telescope operators at the HET for the skillful execution of our observations with HPF.
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 -