Open AccessInfrared colours for Mira‐like long‐period variables found in the Catalogue
Author(s) -
Whitelock Patricia,
Marang Freddy,
Feast Michael
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03743.x
Subject(s) - physics , astrophysics , photometry (optics) , amplitude , stars , hertzsprung–russell diagram , astronomy , infrared excess , infrared , supergiant , globular cluster , variable star , magnitude (astronomy) , instability strip , stellar evolution , cepheid variable , quantum mechanics
Near‐infrared, JHKL , photometry is presented for 193 Mira and semi‐regular variables that were observed by Hipparcos; periods, bolometric magnitudes and amplitudes are derived for 92 of them. Because of the way in which the Hipparcos targets were selected, this group of stars provides a useful data base of Miras with low mass‐loss rates Various period–colour relationships are discussed in detail. The colour, particularly at a given period is found to depend on the pulsation amplitude of the star. A comparison with models suggests that this is a consequence of atmospheric extension, in the sense that large‐amplitude pulsators have very extended atmospheres and redder and but bluer than their lower amplitude counterparts. The stars with very extended atmospheres also have higher values of and hence higher mass‐loss rates. This finding provides further evidence for the causal connection between pulsation and mass loss. Two sequences are identified in the versus log P diagram (where Hp is the Hipparcos broad‐band magnitude) at short periods At a given period these two groups have, on average, the same pulsation amplitude, but different JHKL colours and spectral types. The short‐period stars in the bluer sequence have similar near‐infrared colours to the Miras found in globular clusters. Long‐term trends in the infrared light curves are discussed for stars that have sufficient data.