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J/PAZh/43/460        AI CMi UBV light curves                  (Arkhipova+, 2017)

AI Canis Minoris, a pulsating low-mass supergiant at an early transition phase from the AGB to the post-AGB stage of evolution. Arkhipova V.P., Ikonnikova N.P., Esipov V.F., Komissarova G.V. <Pis'ma Astron. Zh. 43, 460 (2017)> =2017AstL...43..416A =2017PAZh...43..460A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Stars, variable ; Photometry, UBV Keywords: post-AGB supergiants - photometric and spectroscopic observations - semiregular variable stars - AGB and post-AGB stellar evolution - dust shells - masers Abstract: The U BV photometry and low-resolution spectroscopy for the semiregular variable AI CMi, a candidate for post-AGB objects, performed in 1996-2016 and 2000-2013, respectively, are presented. The star showed multiperiodic brightness variations with an amplitude up to 1.5m in the V band, a significant (up to 0.4m) bluing of the B-V and U-B colors as the star faded, and a change of its spectrum from G5 I to K3-5 I, depending on its brightness. A possible long-term fading of AI CMi below 8.5m in the period from May 2013 to early 2015 is observed in the light curve. The colors in this episode did not change the pattern of their unusual behavior with brightness. The main feature of the spectrum for AI CMi is the appearance and strengthening of TiO absorption bands as its brightness declines, which are atypical in the spectra of ordinary G5-K3 supergiants. The bluing of the B-V and U-B colors is interpreted as the blanketing of stellar radiation predominantly in V (and to a lesser extent in B) by the TiO absorption bands whose intensity increases dramatically with decreasing brightness. Another cause of the bluing can be the scattering of stellar radiation by small dust particles in the gas-dust shell of AI CMi. The star's continuum-normalized spectra over the period from 2000 to 2013 in the wavelength range 4200 to 7700 or 9200Å are presented. These were taken at different phases of the pulsation cycle and clearly demonstrate the behavior of the TiO absorption bands depending on the V magnitude and B-V color. The equivalent widths of individual TiO bands were measured, and their correlation with the photometric parameters of the star is shown. AI CMi belongs to the O-rich branch of AGB/post-AGB supergiants and has a luminosity of ∼4000L at a distance of 1500±700pc. The mass of AI CMi is most likely small and close to the lower mass limit for post-AGB stars. The connection of the star's pulsational activity and nonstationary wind with the formation of its molecular and dust shells is discussed briefly. Description: The UBV observations of AI CMi were carried out at the Crimean Station of the SAI MSU using a 60-cm Zeiss reflector with a photoelectric photometer designed by Lyuty (1971, Soobshch. GAISh, No. 172, 30) with a 27" aperture. We began to observe AI CMi in 1996 and obtained more than 200 UBV magnitude estimates for the star in 21 years. Table 1 presents our UBV photometry for AI CMi reduced to the Johnson system. Objects: -------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------- 07 35 41.15 +00 14 58.0 AI CMi = V* AI CMi -------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 25 206 UBV observations of AI CMi in 1996-2016
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 7 I7 d JD Julian date 9- 13 F5.3 mag Vmag Johnson V magnitude 15- 19 F5.3 mag B-V Johnson B-V colour index 21- 25 F5.3 mag U-B Johnson U-B colour index
Acknowledgements: Natalia Ikonnikova, ikonnikova(at)gmail.com
(End) Patricia Vannier [CDS] 12-Jul-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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