Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Full Refereed Journal Article (PDF/Postscript)
· Full Refereed Scanned Article (GIF)
· References in the article
· Citations to the Article (34) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (1)
· Also-Read Articles (Reads History)
· Translate This Page
The activity cycle of Sigma Draconis
Gray, David F.; Baliunas, Sallie L.; Lockwood, G. W.; Skiff, Brian A.
AA(Western Ontario Univ., London, Canada), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(Lowell Observatory, Flagstaff, AZ), AD(Lowell Observatory, Flagstaff, AZ)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 400, no. 2, p. 681-691. (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
Dwarf Stars, Line Spectra, Stellar Activity, Stellar Spectrophotometry, Stellar Temperature, Metallicity, Solar Cycles, Solar Granulation
Bibliographic Code:


Investigations of the temperature and granulation of Sigma Draconis (HR 7462, HD 185144, K0 V) are discussed. Temperature is monitored using a line-depth ratio, and temperature variations of about 5 K are seen. Intermediate-band photometry and Ca II H and K-line emission mimic the temperature changes: a monotonic decline from the 1984 season, a smooth minimum around 1988, followed by a rise back to the 1984 values at the current time. The temperature variations are physically compatible with the photometric ones, implying a constant radius over the activity cycle. Granulation is invariant during this portion of the activity cycle, at least to the level of about +/- 3 m/s, or about +/- 5 percent. The temperature variations by themselves can also be interpreted as rotational modulation with a 20.3-d period, but no evidence of this period is seen in the photometry, the H and K emission, or the line asymmetries, and it is argued to be a chance occurrence.

Printing Options

Print whole paper
Print Page(s) through

Return 600 dpi PDF to Acrobat/Browser. Different resolutions (200 or 600 dpi), formats (Postscript, PDF, etc), page sizes (US Letter, European A4, etc), and compression (gzip,compress,none) can be set through the Printing Preferences

More Article Retrieval Options

HELP for Article Retrieval

Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)


Find Similar Abstracts:

Use: Authors
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
arXiv e-prints