27 research outputs found
Ubv CCD Standards Near 5C1 Radio Sources at Intermediate Galactic Latitude-I
We have been doing a photometric and astrometric sample survey programme on
Schmidt plates in a few selected directions in the Galaxy with an aim to study
galactic stellar populations. In order to calibrate Schmidt plates
photometrically, it is necessary to have a number of photometric standards
which cover the entire range of magnitudes to be studied on the plates. As
Schmidt plates cover a wide area of the sky, the standards should also be
spread over the surface of the plate so as to minimise geometrical effects
present on the plate. This paper is first in a series of papers aimed at to
provide photometric standards in the selected galactic directions to be
studied. In this paper we present photometric magnitudes obtained through CCD
observation in the galactic direction (l=170deg, b=45deg) centered at
alpha(2000) = 9h 41m 20s and delta(2000) = +49deg 54' 20'' and covering an area
of 14 sq degs. B and V magnitudes have been obtained for a total of 214 stars
out of which for 73 stars U magnitudes also have been obtained. The magnitude
range covered is 11<V<21 and 0.18<B-V<1.85.Comment: Postscript file, 13 pages, 1 figure (figure available on request),
paper accepted for publication in the Bulletin of Astronomical Society of
Indi
CCD photometry and astrometry for visual double and multiple stars of the HIPPARCOS catalogue
We present new astrometric and photometric data for 253 visual double stars
of the "intermediate" class, i.e. with angular separations in the range 1
to 15 arcsec. The multi-colour observations were obtained in 1992-94 as part of
the ESO Key Programme "Visual Double Stars" performed at La Silla Observatory (Chile).
Differential magnitudes and colours have been secured in a systematic way while
component magnitudes and colour indices have been determined in the V and I passbands
of the Cousins standard system in good photometric conditions only. Internal and
mean external errors are smaller than respectively 0.01 mag and a few
hundreths of a
magnitude (typically less than 0.03 mag). Relative positions
are obtained as a by-product with internal errors of the order of 0.006´´in angular
separation (corresponding to pixel width ) and 0.07°in position angle. Final accuracies are thoroughly
discussed: we illustrate the overall excellent quality of the data and estimate the quality
degradation for angular separations barely larger than the width of the seeing disk
Hemangiopericytoma of the pancreas: Report of a case and review of the literature
Hemangiopericytoma is an uncommon vascular tumor with variable malignant potential. The origin, structure and function of pericytes remains controversial. Intra-abdominal hemangiopericytomas are highly aggressive soft tissue tumors with a great propensity for malignant transformation. We report on a case of hemangiopericytoma of the pancreas in a 53-year-old female presenting with abdominal pain. Ultrasonography and CT scan revealed a cystic tumor of the head of the pancreas. The patient underwent successful pancreaticoduodenal resection and is alive with no signs of recurrence 25 months following surgery. Ultrastructural studies are necessary to differentiate hemangiopericytomas from other sarcomas. Malignancy may be ascertained only in the presence of metastases or local recurrence. Routine surveillance is advocated
The Hipparcos Input Catalogue: I. Star Selection
International audienc