1,857 research outputs found
New surveys of UBV photometry and absolute proper motions at intermediate latitude
A photometric and proper motion survey has been obtained in 2 directions at
intermediate latitude: (, ;
,) and
(, ; ,
). The survey covers 7.13 and 20.84 square
degrees, respectively. The limiting magnitude is about 18.5 in V for both
directions. We have derived the density laws for stars (M 3.5) as a
function of distance from the galactic plane. The density laws for stars follow
a sum of two exponentials with scale heights of 240 pc (thin disk) and 790 pc
(thick disk), respectively. The local density of thick disk is found to be
6.13 % relative to the thin disk. The kinematical distribution of stars
has been probed to distances up to 3.5 kpc above the galactic plane. New
estimates of the parameters of velocity ellipsoid have been derived for the
thick disk of the Galaxy. A comparison of our data sets with the Besan\c con
model star count predictions has been performed, giving a good agreement in the
magnitude range V = 13 to 18.Comment: 13 pages, 8 PS figures, To appear in A&
Effect of Hedging-Integrated Rule Curves on the Performance of the Pong Reservoir (India) During Scenario-Neutral Climate Change Perturbations
This study has evaluated the effects of improved, hedging-integrated reservoir rule
curves on the current and climate-change-perturbed future performances of the Pong reservoir,
India. The Pong reservoir was formed by impounding the snow- and glacial-dominated Beas
River in Himachal Pradesh. Simulated historic and climate-change runoff series by the
HYSIM rainfall-runoff model formed the basis of the analysis. The climate perturbations used
delta changes in temperature (from 0° to +2 °C) and rainfall (from −10 to +10 % of annual
rainfall). Reservoir simulations were then carried out, forced with the simulated runoff
scenarios, guided by rule curves derived by a coupled sequent peak algorithm and genetic
algorithms optimiser. Reservoir performance was summarised in terms of reliability, resilience,
vulnerability and sustainability. The results show that the historic vulnerability reduced from
61 % (no hedging) to 20 % (with hedging), i.e., better than the 25 % vulnerability often
assumed tolerable for most water consumers. Climate change perturbations in the rainfall
produced the expected outcomes for the runoff, with higher rainfall resulting in more runoff
inflow and vice-versa. Reduced runoff caused the vulnerability to worsen to 66 % without
hedging; this was improved to 26 % with hedging. The fact that improved operational practices
involving hedging can effectively eliminate the impacts of water shortage caused by climate
change is a significant outcome of this study
The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds
Given the rarity of young O star candidates, compact HII regions embedded in
dense molecular cores continue to serve as potential sites to peer into the
details of high-mass star formation. To uncover the ionizing sources of the
most luminous and compact HII regions embedded in the RCW106 and RCW122 giant
molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus
providing an opportunity to examine spatial scales of a few hundred to a
thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra
(R=350), including the fine structure lines [ArIII] and [NeII], were obtained
for four luminous compact HII regions, embedded inside the dense cores within
the RCW106 and RCW122 molecular cloud complexes. At this resolution, these
targets reveal point-like sources surrounded by nebulosity of different
morphologies, uncovering details at spatial dimensions of <1000AU. The
point-like sources display [ArIII] and [NeII] lines - the ratios of which are
used to estimate the temperature of the embedded sources. The derived
temperatures are indicative of mid-late O type objects for all the sources with
[ArIII] emission. Previously known characteristics of these targets from the
literature, including evidence of disk or accretion suggest that the identified
sources may grow more to become early-type O stars by the end of the star
formation process
On the shell star pleione (BU Tauri)
BU Tauri (Pleione) an interesting star in the Pleiades cluster, has been observed spectrophotometrically. The energy distribution curves of the star have been discussed vis a vis model atmospheres for normal stars in the appropriate range of temperature and effective gravity. The changes in the energy distribution curve noticed during our observations and previous observations taken from the literature have been pointed out. On the basis of the measured Há emission equivalent width, a rough estimate of the dimensions of the extended envelope of the star has been made
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