10 research outputs found
Study of variable stars in the MOA data base: long-period red variables in the Large Magellanic Cloud
One hundred and forty six long-period red variable stars in the Large
Magellanic Cloud (LMC) from the three year MOA project database were analysed.
A careful periodic analysis was performed on these stars and a catalogue of
their magnitudes, colours, periods and amplitudes is presented. We convert our
blue and red magnitudes to band values using 19 oxygen-rich stars. A group
of red short-period stars separated from the Mira sequence has been found on a
(log P, K) diagram. They are located at the short period side of the Mira
sequence consistent with the work of Wood and Sebo (1996). There are two
interpretations for such stars; a difference in pulsation mode or a difference
in chemical composition. We investigated the properties of these stars together
with their colour, amplitude and periodicity. We conclude that they have small
amplitudes and less regular variability. They are likely to be higher mode
pulsators. A large scatter has been also found on the long period side of the
(log P, K) diagram. This is possibly a systematic spread given that the blue
band of our photometric system covers both standard B and V bands and affects
carbon-rich stars.Comment: 19 pages, 19 figures, accepted for publication in MNRA
The interstellar medium towards the Ara OB1 region
We present high resolution (R ~ 4 km/s) absorption measurements of the
interstellar NaI and CaII lines measured towards 14 early-type stars of
distance 123 pc - 1650 pc, located in the direction of the Ara OB1 stellar
cluster. The line profiles can broadly be split into four distinct groupings of
absorption component velocity, and we have attempted to identify an origin and
distance to each of these interstellar features. For gas with absorption
covering the velocity range -10 km/s < V_helio < +10 km/s, we can identify the
absorbing medium with local gas belonging to the Lupus-Norma interstellar
cavity located between 100 and 485 pc in this galactic direction. Gas with
velocities spanning the range -20 km/s < V_helio < +20 km/s is detected towards
stars with distances of 570-800 pc. We identify a wide-spread interstellar
feature at V_helio ~ -15 km/s with the expanding HI shell called GSH 337+00-05,
which is now placed at a distance of ~530 pc.Comment: 12 pages, 5 figures, accepted for publication in Astrophysics & Space
Scienc
Insulin treated diabetes mellitus: causes of death determined from record linkage of population based registers in Leicestershire, UK.
Potential Direct Single-Star Mass Measurement
28 pages including 7 figures. Submitted to ApJWe analyze the lightcurve of the microlensing event OGLE-2003-BLG-175/MOA-2003-BLG-45 and show that it has two properties that, when combined with future high resolution astrometry, could lead to a direct, accurate measurement of the lens mass. First, the lightcurve shows clear signs of distortion due to the Earth\'s accelerated motion, which yields a measurement of the projected Einstein radius \\tilde r_E. Second, from precise astrometric measurements, we show that the blended light in the event is coincident with the microlensed source to within about 15 mas. This argues strongly that this blended light is the lens and hence opens the possibility of directly measuring the lens-source relative proper motion \\vec\\mu_\\rel and so the mass M=(c^2/4G)\\mu_\\rel t_E \\tilde r_E, where t_E is the measured Einstein timescale. While the lightcurve-based measurement of \\tilde r_E is, by itself, severely degenerate, we show that this degeneracy can be completely resolved by measuring the direction of proper motion \\vec\\mu_\\rel