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Shivanandan, K.

Publications and source records attributed to Shivanandan, K..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Multiwavelength observations of two B-star nurseries - DR 15 and DR 20

New observations of DR 15 and 20 are reported as part of a study of compact H II regions in the Cyg X region. The radio and FIR data for these objects, when combined with (C-12)O maps, IRAS imagery, and optical photographs, provide new insights into the structure of this complex region and the nature of the star-formation process there. The observations show that DR 15 may consist of one or two B0 ZAMS stars whose H I regions have formed a low-density cavity within a molecular cloud. DR 20 appears to be a young OB cluster. The cluster is dominated by an O5.5 ZAMS star and also contains an approximately 3500-yr-old B0 star appearing as a compact H II region, along with weak FIR sources that may be B0-star candidates.

Odenwald, S. F.↗
NASA NTRS1986

Far-infrared and radio observations of DR 6, DR 7, and DR 22

Far-infrared maps are presented for three young H II regions in the Cygnus X region. DR 6 and 7 were mapped in the wavelength band from 40 to 250 microns at 1 arcmin resolution, while DR 22 was mapped in the same band and also at 100-250 microns, providing dust temperature and optical depth information. New VLA maps of these sources are also presented. It is concluded that DR 6 and 7 are powered by clusters of late O or early B type stars, with ages 100,000 yr or less, while DR 22 appears to be produced by a single O6 ZAMS star. Existing (C-12)O maps suggest that the formation of these objects occurred near the edges of molecular clouds.

Odenwald, S.↗
NASA NTRS1985

Superconducting electromagnetic actuators for astronomical Fabry-Perot interferometers

Two types of superconducting electromagnetic actuators linear and angular - for precise control of Fabry-Perot spectrometer etalons at liquid helium temperature were manufactured and tested successfully. The linear displacement unit (45 Newtons/Amp) has maximum travel of + or - 44 microns with off-axis deviation of less than 1.5 arcseconds for 15 microns path. The angular unit has maximum tilt of + or - 8 arcminutes and can maintain parallelism of two etalons to better than 0.3 arcsecond of angle by compensating the differential contraction upon cooling and off-axis deviation of the linear displacement unit. These actuators are proving especially useful in low temperature infrared instrumentation where other choices, such as piezoelectric crystals, fail and where essentially zero power dissipation permits low infrared backgrounds to be maintained along with long cryogenic lifetimes.

Nishimura, T.↗
NASA NTRS1984

High-resolution far-infrared observations of the extended W51 complex

A far-IR map with 1 arcmin resolution was obtained of the W51 H II region molecular cloud complex. The 40-120 microns survey was performed to study embedded sources which excite the H II gas. The far-IR emission distribution overlapped radio emissions from the region, implying that the extended dust clouds were heated by the same sources as the H II regions. Four compact sources were characterized and associated with concentrations of luminosities that suggested a scarcity of low-mass stars. The brightest source, labeled W51-I, has a luminosity/mass ratio of 150, high enough to indicate a burst of massive O star formation. No triggering mechanism was identified for the burst of star formation.

Rengarajan, T. N.↗
NASA NTRS1984

A liquid helium cooled Fabry-Perot infrared spectrometer

A liquid-helium-cooled Fabry-Perot infrared spectrometer offering excellent performance in the middle infrared range has been constructed and tested. The spectrometer is based on newly developed superconducting actuators which control the alignment and tuning at 4.2 K with virtually no power dissipation within the instrument. Depending on the availability of high-quality etalons, this type of spectrometer should be useful in a wide range of infrared astronomical spectroscopy applications.

Nishimura, T.↗
NASA NTRS1984

Far-infrared sources in the vicinity of the supernova remnant W28

The W28 supernova remnant molecular cloud complex has been surveyed in the 40-250 micron spectral range with a three-sigma sensitivity of 100-165 Jy per beam. Only two sources have been found. One, located near the center of the SNR, has a luminosity of 54,000 solar luminosities and can be identified with the thermal radio source G6.6-0.1. The energizing source is probably an O-type ZAMS star. The second source, which is near the boundary of the SNR at a sharp gradient of OH absorption, has a luminosity of 6000 solar luminosities and has no radio counterpart. It is best explained as a B1 ZAMS star or a pre-main sequence object presumably formed from the impact of an expanding SNR with a molecular cloud. No far-IR emission is observed at the position of the CO molecular cloud, which seems to have been impacted by the SNR.

Odenwald, S. F.↗
NASA NTRS1977

Far infrared observations of IRC + 10216

Results are reported for measurements of IRC + 10216 at 100 microns made with the 91-cm telescope of NASA's Kuiper Airborne Infrared Observatory. The IR photometer employed consisted of a gallium-doped germanium photoconductive detector with a MOSFET preamplifier and load resistor. Signals obtained from the source at modulation frequencies of 30 and 100 Hz are plotted, and the 100-micron flux measurements are shown to be in agreement with previous bolometric measurements. It is noted that the sensitivity of the photoconductive detection system is comparable to that of the conventional bolometers that have been used in airborne IR observations.

Shivanandan, K.↗
NASA NTRS1968

Infrared rocket observations.

IR telescope for rocket observations using liquid nitrogen coolant to eliminate terrestrial and telescope radiation, using InAs and InSb detectors

Harwit, M.↗