Precision Temperatures of Stars

I use the term precision rather than accurate because the temperatures I'm speaking of are relative, star-to-star, or variations of one star with time. The technique that works best is to use the ratio of depths of spectral lines. High resolution spectrographs and light detectors capable of very high precision allow this type of work to be done. Calibration is obtained by looking at the change in line-depth ratio for a group of stars having a range in effective temperature. Fundamental measurements of effective temperature have been done by other people.

The technique of line-depth ratios was recently applied to the sun, and here we find a temperature variation amounting to 1.3-1.5 K over the solar cycle.

Other stars also show temperature variations, some several times larger than the Sun's. See the page on magnetic activity.

References:

• David F. Gray 1996 in Stellar Surface Structure, IAU Symposium 176, (Kluwer: Dordrecht), K.G. Strassmeier & J.L. Linsky, eds., p. 227, The Determination of Temperature from Spectral Lines.
• David F. Gray & W.C. Livingston 1996 Astrophys. J. 474, 802, Monitoring the Solar Temperature: Spectroscopic Temperature Variations of the Sun.
• David F. Gray & W.C. Livingston 1996 Astrophys. J. 474, 798, Monitoring the Solar Temperature: Empirical Calibration of the Temperature Sensitivity of C I 5380.
• David F. Gray 1995 Publ. Astron. Soc. Pacific 107, 120, Comparing the Sun with Other Stars Along the Temperature Coordinate.
• David F. Gray 1994 Publ. Astron. Soc. Pacific 106, 1248, Spectral Line-Depth Ratios as Temperature Indicators for Cool Stars.
• David F. Gray & Heather L. Johanson 1991 Publ. Astron. Soc. Pacific 103, 439, Precise Measurements of Stellar Temperatures Using Line-Depth Ratios.

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