Rotational modulation of spectroscopic Zeeman signatures in low-mass stars

Ryan C. Terrien; Allison Keen; Katy Oda; Winter Parts(they/them); Guðmundur Stefánsson; Suvrath Mahadevan; Paul Robertson; Joe P. Ninan; Corey Beard; Chad F. Bender; William D. Cochran; Katia Cunha; Scott A. Diddams; Connor Fredrick; Samuel Halverson; Fred Hearty; Adam Ickler; Shubham Kanodia; Jessica E. Libby-Roberts; Jack Lubin; Andrew J. Metcalf; Freja Olsen; Lawrence W. Ramsey; Arpita Roy; Christian Schwab; Verne V. Smith; Ben Turner

doi:10.3847/2041-8213/ac4fc8

Rotational modulation of spectroscopic Zeeman signatures in low-mass stars

Ryan C. Terrien^*, Allison Keen, Katy Oda, Winter Parts(they/them), Guðmundur Stefánsson, Suvrath Mahadevan, Paul Robertson, Joe P. Ninan, Corey Beard, Chad F. Bender, William D. Cochran, Katia Cunha, Scott A. Diddams, Connor Fredrick, Samuel Halverson, Fred Hearty, Adam Ickler, Shubham Kanodia, Jessica E. Libby-Roberts, Jack LubinAndrew J. Metcalf, Freja Olsen, Lawrence W. Ramsey, Arpita Roy, Christian Schwab, Verne V. Smith, Ben Turner

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

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.

Original language	English
Article number	L11
Pages (from-to)	1-9
Number of pages	9
Journal	Astrophysical Journal Letters
Volume	927
Issue number	1
DOIs	https://doi.org/10.3847/2041-8213/ac4fc8
Publication status	Published - 1 Mar 2022

Bibliographical note

Copyright © 2022. The Author(s). Published by the American Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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Terrien, R. C., Keen, A., Oda, K., Parts(they/them), W., Stefánsson, G., Mahadevan, S., Robertson, P., Ninan, J. P., Beard, C., Bender, C. F., Cochran, W. D., Cunha, K., Diddams, S. A., Fredrick, C., Halverson, S., Hearty, F., Ickler, A., Kanodia, S., Libby-Roberts, J. E., ... Turner, B. (2022). Rotational modulation of spectroscopic Zeeman signatures in low-mass stars. Astrophysical Journal Letters, 927(1), 1-9. [L11]. https://doi.org/10.3847/2041-8213/ac4fc8

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title = "Rotational modulation of spectroscopic Zeeman signatures in low-mass stars",

abstract = "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 {\AA} 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.",

author = "Terrien, {Ryan C.} and Allison Keen and Katy Oda and Winter Parts(they/them) and Gu{\dh}mundur Stef{\'a}nsson and Suvrath Mahadevan and Paul Robertson and Ninan, {Joe P.} and Corey Beard and Bender, {Chad F.} and Cochran, {William D.} and Katia Cunha and Diddams, {Scott A.} and Connor Fredrick and Samuel Halverson and Fred Hearty and Adam Ickler and Shubham Kanodia and Libby-Roberts, {Jessica E.} and Jack Lubin and Metcalf, {Andrew J.} and Freja Olsen and Ramsey, {Lawrence W.} and Arpita Roy and Christian Schwab and Smith, {Verne V.} and Ben Turner",

note = "Copyright {\textcopyright} 2022. The Author(s). Published by the American Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.",

year = "2022",

month = mar,

day = "1",

doi = "10.3847/2041-8213/ac4fc8",

language = "English",

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Terrien, RC, Keen, A, Oda, K, Parts(they/them), W, Stefánsson, G, Mahadevan, S, Robertson, P, Ninan, JP, Beard, C, Bender, CF, Cochran, WD, Cunha, K, Diddams, SA, Fredrick, C, Halverson, S, Hearty, F, Ickler, A, Kanodia, S, Libby-Roberts, JE, Lubin, J, Metcalf, AJ, Olsen, F, Ramsey, LW, Roy, A, Schwab, C, Smith, VV & Turner, B 2022, 'Rotational modulation of spectroscopic Zeeman signatures in low-mass stars', Astrophysical Journal Letters, vol. 927, no. 1, L11, pp. 1-9. https://doi.org/10.3847/2041-8213/ac4fc8

TY - JOUR

T1 - Rotational modulation of spectroscopic Zeeman signatures in low-mass stars

AU - Terrien, Ryan C.

AU - Keen, Allison

AU - Oda, Katy

AU - Parts(they/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 - Copyright © 2022. The Author(s). Published by the American Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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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DO - 10.3847/2041-8213/ac4fc8

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VL - 927

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EP - 9

JO - Astrophysical Journal Letters

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ER -

Rotational modulation of spectroscopic Zeeman signatures in low-mass stars

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