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Title: CONSTRAINTS ON THE UBIQUITY OF CORONAL X-RAY CYCLES

Abstract

Stellar activity cycles are known to be a widespread phenomenon amongst moderately active solar- and late-type stars from long-term periodic variations in chromospheric Ca II H and K emission lines, yet to date, only a handful of coronal X-ray cycles are known. We have surveyed serendipitously observed stellar sources in fields observed multiple times in the last decade by XMM-Newton and present our analysis of nine stars from six fields. Since our sample is flux-limited, it is strongly biased toward higher levels of X-ray activity. We fit a single temperature APEC spectrum to each source and search for significant periodicities using a Lomb-Scargle periodogram. We use a Monte Carlo (MC) algorithm to yield robust analysis of the statistical significance of cycle detections and non-detections. None of the nine stellar light curves show any convincing indications of periodicity. From MC simulations, we simulate the detection capabilities of our methodology and, assuming a uniform distribution of cycle periods and strengths over the domain searched, we conclude with 95% confidence that less than 72% of the stars represented by our sample of active stars have 5-13 year coronal X-ray cycles.

Authors:
 [1]; ;  [2]
  1. Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22086379
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALGORITHMS; ASTRONOMY; ASTROPHYSICS; CALCIUM IONS; COMPUTERIZED SIMULATION; COSMIC X-RAY SOURCES; DIAGRAMS; EMISSION SPECTRA; MAIN SEQUENCE STARS; MONTE CARLO METHOD; PERIODICITY; PHOTON EMISSION; STELLAR ACTIVITY; STELLAR CORONAE; VISIBLE RADIATION; X RADIATION

Citation Formats

Hoffman, John, Guenther, Hans M., and Wright, Nicholas J., E-mail: hoffma24@illinois.edu, E-mail: guenther@head.cfa.harvard.edu, E-mail: nwright@cfa.harvard.edu. CONSTRAINTS ON THE UBIQUITY OF CORONAL X-RAY CYCLES. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/2/145.
Hoffman, John, Guenther, Hans M., & Wright, Nicholas J., E-mail: hoffma24@illinois.edu, E-mail: guenther@head.cfa.harvard.edu, E-mail: nwright@cfa.harvard.edu. CONSTRAINTS ON THE UBIQUITY OF CORONAL X-RAY CYCLES. United States. doi:10.1088/0004-637X/759/2/145.
Hoffman, John, Guenther, Hans M., and Wright, Nicholas J., E-mail: hoffma24@illinois.edu, E-mail: guenther@head.cfa.harvard.edu, E-mail: nwright@cfa.harvard.edu. Sat . "CONSTRAINTS ON THE UBIQUITY OF CORONAL X-RAY CYCLES". United States. doi:10.1088/0004-637X/759/2/145.
@article{osti_22086379,
title = {CONSTRAINTS ON THE UBIQUITY OF CORONAL X-RAY CYCLES},
author = {Hoffman, John and Guenther, Hans M. and Wright, Nicholas J., E-mail: hoffma24@illinois.edu, E-mail: guenther@head.cfa.harvard.edu, E-mail: nwright@cfa.harvard.edu},
abstractNote = {Stellar activity cycles are known to be a widespread phenomenon amongst moderately active solar- and late-type stars from long-term periodic variations in chromospheric Ca II H and K emission lines, yet to date, only a handful of coronal X-ray cycles are known. We have surveyed serendipitously observed stellar sources in fields observed multiple times in the last decade by XMM-Newton and present our analysis of nine stars from six fields. Since our sample is flux-limited, it is strongly biased toward higher levels of X-ray activity. We fit a single temperature APEC spectrum to each source and search for significant periodicities using a Lomb-Scargle periodogram. We use a Monte Carlo (MC) algorithm to yield robust analysis of the statistical significance of cycle detections and non-detections. None of the nine stellar light curves show any convincing indications of periodicity. From MC simulations, we simulate the detection capabilities of our methodology and, assuming a uniform distribution of cycle periods and strengths over the domain searched, we conclude with 95% confidence that less than 72% of the stars represented by our sample of active stars have 5-13 year coronal X-ray cycles.},
doi = {10.1088/0004-637X/759/2/145},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}