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The He I D3 Line as a Proxy for Magnetic Activity using EXPRES Solar Observations
Momo Ellwarth, Joe Llama, Lily L. Zhao +6
Stellar activity remains one of the primary challenges in the detection and characterization of low-mass exoplanets, as it can induce radial velocity (RV) variations that mask or m…
X-Ray, UV, and Optical Observations of Proxima Centauri's Stellar Cycle
B. J. Wargelin, S. H. Saar, Z. A. Irving +3
Proxima Cen (GJ 551; dM5.5e) is one of only about a dozen fully convective stars known to have a stellar cycle, and the only one to have long-term X-ray monitoring. A previous anal…
The Mean Longitudinal Magnetic Field and its Uses in Radial-Velocity Surveys
F. Rescigno, A. Mortier, X. Dumusque +14
This work focuses on the analysis of the mean longitudinal magnetic field as a stellar activity tracer in the context of small exoplanet detection and characterisation in radial-ve…
Characterizing Solar Center-to-Limb Radial-Velocity Variability with SDO
Michael L. Palumbo, Steven H. Saar, Raphaëlle D. Haywood
Stellar photospheric inhomogeneities are a significant source of noise which currently precludes the discovery of Earth-mass planets orbiting Sun-like stars with the radial-velocit…
Multicomponent Activity Cycles using Hilbert-Huang Analysis
E. N. Velloso, F. Anthony, J. D. do Nascimento +3
The temporal analysis of stellar activity evolution is usually dominated by a complex trade-off between model complexity and interpretability, often by neglecting the non-stationar…
Asteroseismology and Spectropolarimetry of the Exoplanet Host Star Serpentis
Travis S. Metcalfe, Derek Buzasi, Daniel Huber +31
The bright star Ser hosts a hot Neptune with a minimum mass of 13.6 and a 15.5 day orbit. It also appears to be a solar analog, with a mean rotation period of 25.8 d…
Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution
Zackery A. Irving, Steven H. Saar, Bradford J. Wargelin +1
An dynamo, combining shear and cyclonic convection in the tachocline, is believed to generate the solar cycle. However, this model cannot explain cycles in fast rotators (with…
Differences in physical properties of coronal bright points and their ALMA counterparts within and outside coronal holes
F. Matković, R. Brajša, M. Temmer +6
This study investigates and compares brightness and area of coronal bright points (CBPs) inside and outside of coronal holes (CHs) using the single-dish Band 6 observations by the…
X-ray Activity Variations and Coronal Abundances of the Star-Planet Interaction candidate HD 179949
Anshuman Acharya, Vinay L. Kashyap, Steven H. Saar +2
We carry out detailed spectral and timing analyses of the X-ray data of HD 179949, a prototypical example of a star with a close-in giant planet with possible star-planet…
HD 166620: Portrait of a Star Entering a Grand Magnetic Minimum
Jacob K. Luhn, Jason T. Wright, Gregory W. Henry +2
HD 166620 was recently identified as a Maunder Minimum candidate based on nearly 50 years of Ca II H & K activity data from Mount Wilson and Keck-HIRES (Baum et al. 2022). These da…
Magnetic and Rotational Evolution of CrB from Asteroseismology with TESS
Travis S. Metcalfe, Jennifer L. van Saders, Sarbani Basu +15
During the first half of main-sequence lifetimes, the evolution of rotation and magnetic activity in solar-type stars appears to be strongly coupled. Recent observations suggest th…
ALMA small-scale features in the quiet Sun and active regions
R. Brajsa, I. Skokic, D. Sudar +5
Aims. The main aim of the present analysis is to decipher (i) the small-scale bright features in solar images of the quiet Sun and active regions obtained with the Atacama Large Mi…
Long-term stellar activity variations and their effect on radial-velocity measurements
Jean C. Costes, Christopher A. Watson, Ernst de Mooij +8
Long-term stellar activity variations can affect the detectability of long-period and Earth-analogue extrasolar planets. We have, for 54 stars, analysed the long-term trend of five…
Estimating Magnetic Filling Factors From Simultaneous Spectroscopy and Photometry: Disentangling Spots, Plage, and Network
T. W. Milbourne, D. F. Phillips, N. Langellier +21
State of the art radial velocity (RV) exoplanet searches are limited by the effects of stellar magnetic activity. Magnetically active spots, plage, and network regions each have di…
When Do Stalled Stars Resume Spinning Down? Advancing Gyrochronology with Ruprecht 147
Jason Lee Curtis, Marcel A. Agüeros, Sean P. Matt +17
Recent measurements of rotation periods () in the benchmark open clusters Praesepe (670 Myr), NGC 6811 (1 Gyr), and NGC 752 (1.4 Gyr) demonstrate that, after convergi…
Rotation of solar analogs cross-matching Kepler and Gaia DR2
Jose-Dias do Nascimento, Leandro de Almeida, Eduardo Nunes Velloso +10
A major obstacle to interpreting the rotation period distribution for main-sequence stars from Kepler mission data has been the lack of precise evolutionary status for these object…
The spectral impact of magnetic activity on disk-integrated HARPS-N solar observations: exploring new activity indicators
A. P. G. Thompson, C. A. Watson, R. D. Haywood +21
Stellar activity is the major roadblock on the path to finding true Earth-analogue planets with the Doppler technique. Thus, identifying new indicators that better trace magnetic a…
Testing the Spectroscopic Extraction of Suppression of Convective Blueshift
M. Miklos, T. W. Milbourne, R. D. Haywood +21
Efforts to detect low-mass exoplanets using stellar radial velocities (RVs) are currently limited by magnetic photospheric activity. Suppression of convective blueshift is the domi…
Stars at High Spatial Resolution
Kenneth G. Carpenter, Gerard van Belle, Alexander Brown +19
We summarize some of the compelling new scientific opportunities for understanding stars and stellar systems that can be enabled by sub-milliarcsec (sub-mas) angular resolution, UV…
Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations
J. Maldonado, D. F. Phillips, X. Dumusque +29
(Abridged) We perform a detailed study of the main optical activity indicators (Ca II H & K, Balmer lines, Na I D D, and He I D) measured for the Sun…
Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum
A. Collier Cameron, A. Mortier, D. Phillips +33
The time-variable velocity fields of solar-type stars limit the precision of radial-velocity determinations of their planets' masses, obstructing detection of Earth twins. Since 20…
HARPS-N Solar Radial-Velocity Variations Are Dominated By Large, Bright Magnetic Regions
T. W. Milbourne, R. D. Haywood, D. F. Phillips +37
State of the art radial-velocity (RV) exoplanet searches are currently limited by RV signals arising from stellar magnetic activity. We analyze solar observations acquired over a 3…
Observations of the solar chromosphere with ALMA and comparison with theoretical models
R. Brajša, D. Sudar, I. Skokic +9
In this work we use solar observations with the ALMA radio telescope at the wavelength of 1.21 mm. The aim of the analysis is to improve understanding of the solar chromosphere, a…
Optical, UV, and X-Ray Evidence for a 7-Year Stellar Cycle in Proxima Centauri
B. J. Wargelin, S. H. Saar, G. Pojmański +2
Stars of stellar type later than about M3.5 are believed to be fully convective and therefore unable to support magnetic dynamos like the one that produces the 11-year solar cycle.…