8,218 research outputs found
UBVRI CCD photometry of the OB associations Bochum 1 and Bochum 6
We report the first deep CCD photometry of 2460 stars in the field of
two poorly studied OB associations Bochum 1 and Bochum 6. We selected 15 and 14
probable members in Bochum 1 and Bochum 6 respectively using photometric
criteria and proper motion data of Tycho 2. Our analysis indicates variable
reddening having mean value of 0.470.10 and 0.710.13 mag
for Bochum 1 and Bochum 6 respectively. Using the zero-age main-sequence
fitting method, we derive a distance of 2.80.4 and 2.50.4 Kpc for
Bochum 1 and Bochum 6 respectively. We obtain an age of 105 Myrs for both
the associations from isochrone fitting. In both associations high and low mass
stars have probably formed together. Within the observational uncertainties,
mass spectrum of the both associations appears to be similar to the Salpeter's
one.Comment: 14 pages, 7 figures, 6 tables. Accepted for Bull. Astr. Soc. Indi
Non-uniform extinction in young open star clusters
The extinction law and the variation of colour excess with position,
luminosity as well as spectral class in young open star clusters NGC 663,
NGC869, NGC 884, NGC 1502, NGC 1893, NGC 2244, NGC 2264, NGC 6611, Tr 14, Tr
15,Tr 16, Coll 228, Tr 37 and Be 86 have been studied. The difference in the
minimum and maximum values of E(B-V) of cluster members has been considered as
a measure of the presence of non-uniform gas and dust inside the clusters. Its
value ranges from 0.22 to 1.03 mag in clusters under study, which indicates
that non-uniform extinction is present in all the clusters. It has been noticed
for the first time in NGC 1502 and Tr 37. It is also found that the
differential colour excess in open clusters, which may be due to the presence
of gas and dust, decreases systematically with the age of clusters indicating
that matter is used either in star formation or blown away by hot stars or
both. There is no uniformity in the variation of E(B-V) with either position or
spectral class or luminosity.Comment: 11 pages, 8 figures, 4 tables; accepted for publication in MNRAS,
typos adde
Luffa aegyptiaca (Gourd) Fruit Juice as a Source of Peroxidase
Peroxidases have turned out to be potential biocatalyst for a variety of organic reactions. The research work reported in this communication was done with the objective of finding a convenient rich source of peroxidase which could be used as a biocatalyst for organic synthetic reactions. The studies made have shown that Luffa aegyptiaca (gourd) fruit juice contains peroxidase activity of the order of 180 enzyme unit/mL. The Km values of this peroxidase for the substrates guaiacol and hydrogen peroxide were 2.0 and 0.2 mM, respectively. The pH and temperature optima were 6.5 and 60°C, respectively. Like other peroxidases, it followed double displacement type mechanism. Sodium azide inhibited the enzyme competitively with Ki value of 3.35 mM
Simulations Show that Vortex Flows could Heat the Chromosphere in Solar Plage
The relationship between vortex flows at different spatial scales and their
contribution to the energy balance in the chromosphere is not yet fully
understood. We perform three-dimensional (3D) radiation-magnetohydrodynamic
(MHD) simulations of a unipolar solar plage region at a spatial resolution of
10 km using the MURaM code. We use the swirling-strength criterion that mainly
detects the smallest vortices present in the simulation data. We additionally
degrade our simulation data to smooth-out the smaller vortices, so that also
the vortices at larger spatial scales can be detected. Vortex flows at various
spatial scales are found in our simulation data for different effective spatial
resolutions. We conclude that the observed large vortices are likely clusters
of much smaller ones that are not yet resolved by observations. We show that
the vertical Poynting flux decreases rapidly with reduced effective spatial
resolutions and is predominantly carried by the horizontal plasma motions
rather than vertical flows. Since the small-scale horizontal motions or the
smaller vortices carry most of the energy, the energy transported by vortices
deduced from low resolution data is grossly underestimated. In full resolution
simulation data, the Poynting flux contribution due to vortices is more than
adequate to compensate for the radiative losses in plage, indicating their
importance for chromospheric heating.Comment: 8 pages, 5 figures, accepted in ApJ
BVRI CCD photometric standards in the field of GRB 990123
The CCD magnitudes in Johnson and Cousins photometric passbands are
determined for 18 stars in the field of GRB 990123. These measurements can be
used in carrying out precise CCD photometry of the optical transient of GRB
990123 using differential photometric techniques during non--photometric sky
conditions. A comparison with previous photometry indicates that the present
photmetry is more precise.Comment: Tex file, 5 pages with 1 figure. Bull. Astron. Society India, Vol. 27
(accepted
- …