3400-7500 Å Energy Distribution and JHKLM Photometry of Solar-Type Stars

Irina N. GLushneva

Sternberg Astronomical Institute, Moscow State University
413 Universitetskij Prospect, 119899 Moscow, Russia

Energy distribution data in the range 3400 - 7500 AA obtained by means of the scanner installed at the 60-cm Zeiss reflector, and JHKLM photometry provided at the 1.25 m reflector of the Sternberg Institute Crimean Station for 8 stars of spectral types G1.5-G3 of V and IV luminosity classes, are presented. The accuracy of the spectrophotometric data is 1.5% in the range 4000 - 6000 AA. and about 2% in the ranges 3400 - 4000 and 6000 - 7500 AA. The accuracy of the JHKLM photometry is 2% in the bands J,H,K and L and 5% in the M band. Comparison of energy distribution in the spectra of stars with three reliable sets of spectrophotometric data of the Sun shows that the temperature of BS 88, BS 7504 and BS 4030 is lower than of the Sun, and the temperature of HD 213575 is near to the solar one.

Comparison of the stellar JHKLM photometry with synthetic solar photometry in these IR bands was done. In the case of the equality of J magnitudes of the Sun and BS 7504, the differences of fluxes in K and L bands are maximal (9-13%), while in the H and M bands they are only 1-2%.

JHKLM photometry of different authors is presented. The differences between the measurements of various authors are more in many cases than the accuracy declared.

Comparison of color indices J-H, J-K, J-L, J-M of the solar type stars and of the Sun doesn't permit us to consider these stars as full solar analogs.

1. Introduction

Comparison of solar spectral energy distribution and photometric characteristics of the Sun with the corresponding data for solar type stars may be very useful when we answer the question of whether the Sun is the typical representative of the spectral type G2~V. The Sun is well known to be the standard of this subtype in the MK - classification based on the spectral lines intensities.

The Sun is often used as a standard in the investigations of different parameters of stars such as luminosity, mass, metallicity and so on. It is very important also to know photometric parameters of the Sun, i.e. color indices in different photometric systems. The position of the Sun on the two - color diagrams and comparison with solar type stars positions will make use for the decision of the problem if the Sun is "quite normal" or "slightly peculiar" star.