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S Apodis
Variable star in the constellation Apus From Wikipedia, the free encyclopedia
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S Apodis, also known as HD 133444 is a variable star located in the southern circumpolar constellation Apus. It has an apparent magnitude ranging from 9.6 to 17,[3] which is below the limit for naked eye visibility. The object is located relatively far at a distance of approximately 15,000 light years based on Gaia DR3 parallax measurements,[2] but it is drifting closer with a heliocentric radial velocity of −75 km/s.[7]
HD 133444 was discovered to be a variable star by Williamina Fleming, who examined images of the star on 58 photographic plates taken from 1889 through 1895. The discovery was announced in 1896.[14] Annie Jump Cannon included the star, with its variable star designation S Apodis, in her 1907 Second Catalogue of Variable Stars.[15] However, its nature as a carbon star was not observed until 1967 by astronomer Brian Warner.[16] In 1973, HD 133444 was listed as a R Coronae Borealis variable.[17] These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs[18] and fewer than 100 have been discovered as of 2013.[19] A decade later, S Apodis was observed to have a change it its pulsation mode.[9]
S Apodis has a stellar classification of R3, indicating that it is a R-type carbon star. It has a mass of either 0.6 M☉ or 1 M☉,[9] depending on the model. However, it has expanded to an average radius 132 times that of the Sun.[10] It radiates 960 times the luminosity of the Sun[11] from its photosphere at an effective temperature of 4,500–5,115 K,[12] giving it an orange hue. An infrared excess has been detected around the star, indicating the presence of circumstellar dust. The dust has a temperature of 730 K.[20]
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