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Title: STELLAR ACTIVITY AND ITS IMPLICATIONS FOR EXOPLANET DETECTION ON GJ 176

Abstract

We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 yr from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over six years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one ormore » more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.« less

Authors:
 [1]; ; ;  [2]; ;  [3]
  1. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
  2. Department of Astronomy and McDonald Observatory, University of Texas at Austin, Austin, TX 78712 (United States)
  3. Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Boulevard, Box 9501, Nashville, TN 37209 (United States)
Publication Date:
OSTI Identifier:
22522091
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 801; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DETECTION; INDEXES; MODULATION; ORBITS; PHOTOMETRY; RADIAL VELOCITY; RESOLUTION; ROTATION; SODIUM; STARS; STELLAR ACTIVITY; SURFACES; TELESCOPES; VISIBLE RADIATION

Citation Formats

Robertson, Paul, Endl, Michael, Cochran, William D., MacQueen, Phillip J., Henry, Gregory W., and Williamson, Michael H., E-mail: pmr19@psu.edu. STELLAR ACTIVITY AND ITS IMPLICATIONS FOR EXOPLANET DETECTION ON GJ 176. United States: N. p., 2015. Web. doi:10.1088/0004-637X/801/2/79.
Robertson, Paul, Endl, Michael, Cochran, William D., MacQueen, Phillip J., Henry, Gregory W., & Williamson, Michael H., E-mail: pmr19@psu.edu. STELLAR ACTIVITY AND ITS IMPLICATIONS FOR EXOPLANET DETECTION ON GJ 176. United States. doi:10.1088/0004-637X/801/2/79.
Robertson, Paul, Endl, Michael, Cochran, William D., MacQueen, Phillip J., Henry, Gregory W., and Williamson, Michael H., E-mail: pmr19@psu.edu. Tue . "STELLAR ACTIVITY AND ITS IMPLICATIONS FOR EXOPLANET DETECTION ON GJ 176". United States. doi:10.1088/0004-637X/801/2/79.
@article{osti_22522091,
title = {STELLAR ACTIVITY AND ITS IMPLICATIONS FOR EXOPLANET DETECTION ON GJ 176},
author = {Robertson, Paul and Endl, Michael and Cochran, William D. and MacQueen, Phillip J. and Henry, Gregory W. and Williamson, Michael H., E-mail: pmr19@psu.edu},
abstractNote = {We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 yr from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over six years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.},
doi = {10.1088/0004-637X/801/2/79},
journal = {Astrophysical Journal},
number = 2,
volume = 801,
place = {United States},
year = {Tue Mar 10 00:00:00 EDT 2015},
month = {Tue Mar 10 00:00:00 EDT 2015}
}