The Fainting of α Centauri A, Resolved
Open Access
- 11 April 2008
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 678 (2), L121-L124
- https://doi.org/10.1086/588581
Abstract
Beginning in 2003, XMM-Newton snapshot monitoring of α Centauri (HD 128620, 128621: G2 V, K1 V) documented a steady fading of the primary's X-ray corona, which had all but disappeared by early 2005. The steep decline in LX was at odds with the previous two decades of high-energy measurements, which showed only modest variability of the Sun-like star. A Chandra LETGS spectrum in 2007 June, however, fully resolved the source of the curious X-ray darkening: a depletion of plasma above ~2 MK had substantially depressed the line spectrum where the XMM-Newton response peaks (λ 30 Å), even though the overall coronal luminosity, dominated by longer wavelength emissions, had declined only slightly. This is reminiscent of the Sun's magnetic activity cycle, where the 2-3 MK active regions of sunspot maximum give way to the spatially pervasive, but cycle-independent, 1 MK "quiet corona" at minimum. This emphasizes that any discussion of cyclic coronal variability in low-activity stars will depend crucially on the energy coverage of the measurements.This publication has 13 references indexed in Scilit:
- X-rays from α Centauri – The darkening of the solar twinAstronomy & Astrophysics, 2005
- Convective Dynamos and the Minimum X‐Ray Flux in Main‐Sequence StarsThe Astrophysical Journal, 2005
- High-amplitude, long-term X-ray variability in the solar-type star HD 81809: The beginning of an X-ray activity cycle?Astronomy & Astrophysics, 2004
- An Estimate of the Sun’sROSAT‐PSPC X‐Ray Luminosities UsingSNOE‐SXP MeasurementsThe Astrophysical Journal, 2003
- Chandra-LETGS X-ray observation of α Centauri: A nearby (G2V + K1V) binary systemAstronomy & Astrophysics, 2003
- First Light Measurements of Capella with the Low-Energy Transmission Grating Spectrometer aboard the [ITAL]Chandra X-Ray Observatory[/ITAL]The Astrophysical Journal, 2000
- The Sun as an X‐Ray Star. II. Using theYohkoh/Soft X‐Ray Telescope–derived Solar Emission Measure versus Temperature to Interpret Stellar X‐Ray ObservationsThe Astrophysical Journal, 2000
- AXAF High-Resolution Camera (HRC): calibration and recalibration at XRCF and beyondPublished by SPIE-Intl Soc Optical Eng ,1997
- Einstein detection of X-rays from the Alpha Centauri systemThe Astrophysical Journal, 1982
- X-rays from Alpha CentauriThe Astrophysical Journal, 1978