Living With A Red Dwarf: Rotation, Starspots, Activity Cycles, Coronal X-ray Activity And X-uv Irradiances Of Proxima Centauri

Details Living With A Red Dwarf: Rotation, Starspots, Activity Cycles, Coronal X-ray Activity And X-uv Irradiances Of Proxima Centauri Living With A Red Dwarf: Rotation, Starspots, Activity Cycles, Coronal X-ray Activity And X-uv Irradiances Of Proxima Centauri

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21110311j&link_type=abstract

American Astronomical Society, AAS Meeting #211, #103.11; Bulletin of the American Astronomical Society, Vol. 39, p.921

Astronomy and Astrophysics

Astronomy

Scientific paper

As part of our Living with a Red Dwarf Program, we have carried out a detailed study of the radiative and plasma properties of the nearby dM5.5e star Proxima Centauri. Proxima Cen is noteworthy as the nearest star to the Sun. Because of its proximity ( 4.3 L.Y.) and membership in the α Cen system, Proxima Cen is an important star to use as a surrogate for solar-aged mid-dM stars. It is relatively bright (V = 11-mag) and has well determined observational and physical properties (MV, Teff, [Fe/H], angular diameter, mass and age). Importantly for our purposes, Proxima Cen has a reliable age of 5.5-6.0 Gyr from its association with the α Cen system in which α Cen A (G2 V) has a reliable isochronal age determination. We have analyzed 5 years of ASAS-3, V-band photometry to search for evidence of short- and long-term variations in brightness that could arise from magnetically related phenomenon (star spots, faculae, and possible UV flares). We also examine its coronal X-ray emission and variations as well as the stars chromospheric and transition regions in the UV from IUE and FUSE observations. The X-UV/optical data are combined and irradiances are calculated for use in extrasolar planet studies. From the photometry we find a rotational modulation of Prot = 83.5 days, in excellent agreement with the earlier HST/FGS study of Benedict et al. (1998). The character of its light variations indicates possible differential rotation as well as a probable long-term activity cycle of 6.9 +/- 0.5 yrs. Although Proxima Cen should be a fully convective star with a different magnetic dynamo (α2) than our Sun (αΩ), its overall magnetic behavior appears to be solar-like.
This research is supported by grants from NSF/RUI AST-507536 and NASA Grants NNX06AD386 and NNG04G038G. We are grateful for this support.

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