نتایج جستجو برای: mira stars
تعداد نتایج: 57810 فیلتر نتایج به سال:
We have measured nonzero closure phases for about 29% of our sample of 56 nearby asymptotic giant branch (AGB) stars, using the three-telescope InfraredOptical Telescope Array (IOTA) interferometer at near-infrared wavelengths (H band) and with angular resolutions in the range 5Y10 mas. These nonzero closure phases can only be generated by asymmetric brightness distributions of the target stars...
We reobserved in the $R_C$ and $i'_{Sloan}$ bands, during years 2020-2021, seven Mira variables Cassiopeia, for which historical light curves were available from Asiago Observatory plates taken 1967-84. The aim was to check if any of them had undergone a substantial change period or curve shape. Very recent public data form ZTF-DR5 also used expand our time base window. A marked color detected ...
The time variation in the water-vapour bands in oxygen-rich Mira variables has been investigated using multi-epoch ISO/SWS spectra of four Mira variables in the 2.5–4.0 µm region. All four stars show H2O bands in absorption around minimum in the visual light curve. At maximum, H2O emission features appear in the ∼3.5– 4.0 µm region, while the features at shorter wavelengths remain in absorption...
Hipparcos trigonometrical parallaxes of Mira-type variables have been combined with ground-based angular diameter measurements to derive linear diameters. Of eight stars with ground-based data, six have diameters indicating overtone pulsation whilst two, both with periods over 400 day, are pulsating in the fundamental. Hipparcos parallaxes of 11 Miras have been combined with extensive infrared ...
A survey of CO(3–2) emission from optically visible oxygen–rich Mira variable stars within 500 pc of the sun was conducted. A molecular envelope was detected surrounding 36 of the 66 stars examined. Some of these stars have lower outflow velocities than any Miras previously detected in CO. The average terminal velocity of the ejected material was 7.0 km s 1, about half the value found in Miras ...
JHKs near-infrared photometry of stars in the Phoenix dwarf galaxy is presented and discussed. Combining these data with the optical photometry of Massey et al. allows a rather clean separation of field stars from Phoenix members. The discovery of a Mira variable (P = 425 days), which is almost certainly a carbon star, leads to an estimate of the distance modulus of 23.10 ± 0.18 that is consist...
Interferometric measurements of stellar sizes in frequency bands ranging from the near-infrared to longer wavelengths give different results. Various explanations have been proposed to account for these variations in apparent size with wavelength, but none have been entirely consistent. We propose that thermal ionization in the stellar atmosphere and resulting opacity, primarily due to free-fre...
We describe an observing campaign using the Very Long Baseline Array (VLBA) to monitor the time-evolution of the v = 1, J = 1−0 SiO maser emission towards the Mira variable TX Cam. The data reported here cover the period 1997 May 24 to 1999 February 19, during which the SiO maser emission was im-aged at approximately biweekly intervals. The result is an animated movie at an angular resolution o...
The nearby Mira-like variable L2 Pup is shown to be undergoing an unprecedented dimming episode. The stability of the period rules out intrinsic changes to the star, leaving dust formation along the line of sight as the most likely explanation. Episodic dust obscuration events are fairly common in carbon stars but have not been seen in oxygen-rich stars. We also present a 10-μm spectrum, taken ...
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