8 research outputs found
Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlense H alpha line
We discuss high-resolution, time-resolved spectra of the caustic exit of the
binary microlensing event OGLE 2002-BUL-69 obtained with UVES on the VLT. The
source star is a G5III giant in the Galactic Bulge. During such events, the
source star is highly magnified, and a strong differential magnification around
the caustic resolves its surface. Using an appropriate model stellar atmosphere
generated by the NextGEN code we obtained a model light curve for the caustic
exit and compared it with a dense set of photometric observations obtained by
the PLANET microlensing follow up network. We further compared predicted
variations in the H alpha equivalent width with those measured from our
spectra. While the model and observations agree in the gross features, there
are discrepancies suggesting shortcomings in the model, particularly for the H
alpha line core, where we have detected amplified emission from the stellar
chromosphere as the source star's trailing limb exited the caustic. This
achievement became possible by the provision of the OGLE-III Early Warning
System, a network of small telescopes capable of nearly-continuous
round-the-clock photometric monitoring, on-line data reduction, daily
near-real-time modelling in order to predict caustic crossing parameters, and a
fast and efficient response of a 8m-class telescope to a
``Target-Of-Opportunity'' observation request.Comment: 4 pages Latex, 3 figures, accepted for publication to astronomy and
astrophysics letter
Full characterization of binary-lens event OGLE-2002-BLG-069 from PLANET observations
We analyze the photometric data obtained by PLANET and OGLE on the
caustic-crossing binary-lens microlensing event OGLE-2002-BLG-069. Thanks to
the excellent photometric and spectroscopic coverage of the event, we are able
to constrain the lens model up to the known ambiguity between close and wide
binary lenses. The detection of annual parallax in combination with
measurements of extended-source effects allows us to determine the mass,
distance and velocity of the lens components for the competing models. While
the model involving a close binary lens leads to a Bulge-Disc lens scenario
with a lens mass of M=(0.51 +- 0.15) M_sol and distance of D_L=(2.9 +- 0.4)
kpc, the wide binary lens solution requires a rather implausible binary
black-hole lens (M >=126 M_sol). Furthermore we compare current
state-of-the-art numerical and empirical models for the surface brightness
profile of the source, a G5III Bulge giant. We find that a linear
limb-darkening model for the atmosphere of the source star is consistent with
the data whereas a PHOENIX atmosphere model assuming LTE and with no free
parameter does not match our observations.Comment: 9 pages, 9 figures, accepted by A&
Self-perceived stress reactivity is an indicator of psychosocial impairment at the workplace
BACKGROUND: Work related stress is associated with a range of debilitating health outcomes. However, no unanimously accepted assessment tool exists for the early identification of individuals suffering from chronic job stress. The psychological concept of self-perceived stress reactivity refers to the individual disposition of a person to answer stressors with immediate as well as long lasting stress reactions, and it could be a valid indicator of current as well as prospective adverse health outcomes. The aim of this study was to determine the extent to which perceived stress reactivity correlates with various parameters of psychosocial health, cardiovascular risk factors, and parameters of chronic stress and job stress in a sample of middle-aged industrial employees in a so-called "sandwich-position". METHODS: In this cross-sectional study, a total of 174 industrial employees were assessed for psychosocial and biological stress parameters. Differences between groups with high and low stress reactivity were analysed. Logistic regression models were applied to identify which parameters allow to predict perceived high versus low stress reactivity. RESULTS: In our sample various parameters of psychosocial stress like chronic stress and effort-reward imbalance were significantly increased in comparison to the normal population. Compared to employees with perceived low stress reactivity, those with perceived high stress reactivity showed poorer results in health-related complaints, depression, anxiety, sports behaviour, chronic stress, and effort-reward imbalance. The educational status of employees with perceived low stress reactivity is higher. Education, cardiovascular complaints, chronic stress, and effort-reward imbalance were moderate predictors for perceived stress reactivity. However, no relationship was found between stress reactivity and cardiovascular risk factors in our sample. CONCLUSIONS: Job stress is a major burden in a relevant subgroup of industrial employees in a middle management position. Self-perceived stress reactivity seems to be an appropriate concept to identify employees who experience psychosocial stress and associated psychological problems at the workplace