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1.4 Star characteristics

The list of the 300 brightest stars selected for use by GOMOS measurements is provided in the Appendix B of this document. Over 2003, 177 different stars were used for the occultation measurements.

The star characteristics impact the quality and the accuracy of the measurements and of the retrieved products. The visual magnitude of the star gives an indication of the star brightness. It ranges from -1.44 for the brightest one (Sirius) to 4.5 for the faintest ones. A star is usually considered as being strong if its visual magnitude is lower than 0.8 and as being faint if it is higher than 2. Only stars with a visual magnitude lower than 3.553 are used for the GOMOS measurements.

The spectral type of the star (the shape of its spectrum) is approximated by its effective temperature. It ranges from 2800 K to 39000 K. A star is usually considered as being cold if its effective temperature is lower than 6000 K and as being hot if it is higher than 10000 K.

The signal-to-noise ratio of the measurement depends on both the visual magnitude of the star and its effective temperature.