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Naranan, S.

Publications and source records attributed to Naranan, S..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Balloon observations of hard X-rays from some galactic X-ray sources

An X-ray telescope consisting of 400 cm phoswich detectors (NaI(T1)/CsI(Na)) was flown from Hyderabad (India) on 18 December 1984. The field of view was 5 deg x 5 deg FWHM. In a 10 hour float at 4 MB several galactic X-ray sources were tracked by the telescope using an on-board microprocessor. Fluxes and spectra in 18-120 keV X-rays for SCO X-1, GX 1+4, Gx 5-1, GX 17+2, SCT X-1, CYC X-1 an CYG X-3 will be presented.

Damle, S. V.↗
NASA NTRS1985

Balloon observations of hard X-rays from NGC 4151 and an X-ray transient source

An X-ray telescope consisting of 400 sq cm phoswich detectors (NaI(Tl)/CsI(Na)) was flown from Hyderabad (India) on 31 October 1980; the field of view was 11 deg x 1 deg FWHM. During a five hour observation at 5 millibars two X-ray sources were seen: (1) the variable Seyfert Galaxy NGC 4151; and (2) a transident of approximately 8 minutes duration in the vicinity of the variable source 4U1444 43 which may be associated with the galaxy NGC 5608. X-ray fluxes and spectra in 18-120 keV X-rays are presented.

Kunte, P. K.↗
NASA NTRS1985

Complex structure of the supernova remnant HB 3

HB 3 is an old, large (84 pc diameter) supernova remnant associated with the W3 H II region/molecular cloud complex. Observations of the imaging proportional counter (IPC) onboard the Einstein X-ray astronomy satellite have been reprocessed to yield a contour map of X-ray brightness and spectra of various regions of this remnant. The measured IPC flux is 2.4 x 10 to the -11th ergs per sq cm per s, giving a 0.2-4 keV luminosity of 1.6 x 10 to the 35th ergs/s for a column densityof 6 x 10 to the 21st per sq cm. The measured X-ray temperatures reveal a decrease from center to limb of the remnant of 1-0.3 keV. HB 3 is in the late adiabatic blast-wave phase of evolution, 30,000 to 50,000 yr old and with an initial blast energy of 3 x 10 to the 50th ergs. The X-ray map is compared with available radio and optical images. In X-rays, HB 3 has two components - a diffuse emission inside the 84 pc radio remnant and a ring of emission at the center of 30 pc in diameter. The diffuse emission is similar to that from other supernova remnants which are moderately obscured (column density, nH approximately 10 to the 22nd per sq cm). Three possibilities for the origin of the ring are explored: (1) a second supernova remnant, (2) a shocked shell in the interstellar medium surrounding HB 3, and (3) reverse-shock heated ejecta. There is no hot neutron star within the remnant.

Leahy, D. A.↗
NASA NTRS1985

On fast X-ray rotators with long-term periodicities

The support of previous SAS 3 spacecraft observations by new data gathered by the Monitor Proportional Counter aboard the HEAO 2 spacecraft indicates that the pulse period history of the 13.5 sec-pulsing X-ray source LMC X-4 is consistent with standard accretion and torque models only if LMC X-4 is a fast rotator for which the accretion torques nearly cancel. This result leads to a neutron star magnetic field strength estimate of about 1.2 x 10 to the 13th G. Strong evidence is noted for Her X-1's status as a fast rotator, while SMC X-1 is probably an intermediate-to-fast rotator. In the context of slaved disk models for these objects, it is noted that the precession periods expected for the companion stars are significantly longer than the observed 1-2 month time scales; slaved disk models are thereby undermined.

Naranan, S.↗
NASA NTRS1984

X-ray observations of X Persei

The HEAO 2 Einstein Observatory was used to confirm the identification of 4U 0352 + 30 with X Per. The HEAO 2 data were analyzed in order to determine an additional point in the pulse period history of the X-ray source and to search for short binary periods. In addition, a majority of the historical X-ray observations was reanalyzed and more refined values for the pulse period as a function of time were obtained. The period history possess significant scatter, but no evidence for a measurable long-term spin-up trend is found, and hence a lower limit to the spin-up time scale is set. This lower limit is consistent with the presence of a neutron star, but it does not rule out a degenerate dwarf. The period history was also searched for evidence of binary motion, and upper limits to a(x) sin i were obtained.

Weisskopf, M. C.↗
NASA NTRS1983

X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1

A comparison is presented of the black hole candidates LMC X-3 and Cygnus X-1 based on Einstein observations of LMC X-3 with the monitor proportional counter. A spectral analysis shows LMC X-3 to be more like the typical bright galactic X-ray source than Cygnus X-1. A search for periodic pulsations over a period range from 0.2 ms to over 1000 s set upper limits at the 90 percent confidence level of the order of 10 percent. An analysis of the aperiodic variability of LMC X-3 shows none of the shot noise behavior characteristic of Cygnus X-1. The absence of distinctive X-ray properties common to both sources suggests that the identification of black hole candidates on the basis of X-ray properties similar to Cygnus X-1 (or LMC X-3) is not reliable.

Weisskopf, M. C.↗
NASA NTRS1983

The period history of the X-ray pulsar in MSH 15-52

New and refined mesurements of the pulse period of the X-ray pulsar in the supernova remnant MSH 15-52 are presented. The data were obtained with the Monitor proportional Counter on board the HEAO 2 observatory. The period measurements were obtained by analyzing pulse arrival times determined by cross-correlating sample pulse profiles with a master template. The period history for the source and a representative 0.15 s X-ray light curve are shown. The X-ray measurements alone lead to a refined value of the period derivative of (1.5382 + or -0.0024) x 10 to the -12th s/s, while including the results of more recent radio observations leads to a value of (1.54029 + or -0.00095) x 10 to the -12th s/s. These results indicate a hard-point source surrounded by diffuse nebular emission.

Weisskopf, M. C.↗
NASA NTRS1981

Discovery of X-ray pulsations from 2S 1417-624

X-ray pulsations having a period of 17.64 sec are detected from the hard, variable galactic X-ray source 2S 1417-624. It is noted that the pulsations were found through a Fourier analysis of 40 satellite orbits of data taken with the rotation modulation collimators aboard SAS 3 in July 1978. The pulse profile shows detailed interpulse structure that is similar in character to the pulse profiles of 4U 0900-40 and A0535+26. Significant changes in pulse period are detected over the eight-day observing interval. It is suggested that these changes may be the result of a large intrinsic spin-up rate for the neutron star or from binary orbital motion, with orbital periods longer than approximately 15 days.

Kelley, R. L.↗
NASA NTRS1977

Soft X-ray sources and supernova remnants in Cygnus - Rocket and Apollo-Soyuz results

Soft X-ray observations of the Cygnus region obtained from proportional counters aboard a rocket and also on the Apollo-Soyuz mission are reported. It is found that Cyg X-6, a source whose flux in confined to the 0.5-2.0-keV band, is a long narrow filament oriented nearly perpendicular to the galactic plane. This feature has a linear dimension greater than or of the order of 150 parsecs, and its spectrum is adequately described by an exponential. Another intense soft source whose flux is also confined to the 0.5-2.0-keV band has been discovered near Gamma Cygni. This source, designed Cyg X-7, has a spectrum characterized by a temperature of 1.5 to 5 million K and a hydrogen column density of at least 10 to the 21st power per sq cm. The possible association of Cyg X-7 with the supernova remnant DR 4 is discussed. An interpretation of this object in terms of the standard adiabatic spherical-shock-wave model yields plausible values for the free paramenters. HB 21, another old supernova remnant, has not been detected as a soft X-ray source.

Davidsen, A. F.↗
NASA NTRS1977

X-ray emission from the supernova remnant MSH 14-63

X-ray emission in the 0.6-2.5-keV energy range has been detected from the supernova remnant MSH 14-63. The observed flux is 3.5 by 10 to the -10th power erg/sq cm per sec. The absence of lower-energy X-rays indicates a hydrogen column density consistent with the radio and optical distance estimates of 2.5 kpc.

Naranan, S.↗
NASA NTRS1974

Electron contamination in a mid-latitude soft X-ray astronomy experiment during an intense magnetic storm

A large area X-ray sky survey payload was launched from White Sands Missile Range (106 deg W 32 deg N) on 1 Nov. 1972 at 0530 hours U.T. The launch time coincided with intense geomagnetic activity (3 hour K sub p index = 8) following a solar flare. The data have been analyzed to determine possible contamination of X-ray data by large fluxes of low energy electrons that can precipitate down to low altitudes during magnetic storms. There is clear evidence in the data for low energy electrons of 10 - 50 keV contributing appreciably at about 200 km altitude in the 1 - 10 keV X-ray energy channels of the proportional counters used for the X-ray observations. The McIlwain parameters L and B for this altitude at White Sands are 1.25 and 0.46G, respectively.

Naranan, S.↗