Engineering topics

Kristian, Jerome

Publications and source records attributed to Kristian, Jerome.

4 records

NASA NTRS1993

Imaging of the gravitational lens system PG 1115+080 with the Hubble Space Telescope

This paper is the first of a series presenting observations of gravitational lenses and lens candidates, taken with the Wide Field/Planetary Camera of the HST. We have resolved the gravitational lens system PG 1115+080 into four point sources and a red, extended object that is presumably the lens galaxy; we present accurate relative intensities, colors, and positions of the four images, and lower accuracy intensity and position of the lens galaxy, all at the epoch 1991.2. Comparison with earlier data shows no compelling evidence for relative intensity variations between the QSO components having so far been observed. The new data agree with earlier conclusions that the system is rather simple, and can be produced by the single observed galaxy. The absence of asymmetry in the HST images implies that the emitting region of the quasar itself has an angular radius smaller than about 10 milliarcsec (100 pc for H0 = 50, q0 = 0.5).

Kristian, Jerome↗

NASA NTRS1992

Planetary Camera observations of the M87 stellar cusp

Results are presented of an analysis of V- and I-band HST Planetary Camera images of the giant elliptical galaxy M87 which show that its central starlight distribution is consistent with the black hole 2.6 x 10 exp 9-solar-mass cup model proposed for M87 by Young et al. (1978). A combined approach of image deconvolution and modeling is used to investigate the starlight distribution into limiting radii of about 0.04 arcsec. The central structure of M87 is described by three components: a power-law starlight profile of the form mu(r) varies as r exp -1/4 for r of less than 3 arcsec, a central nonthermal point source, and optical counterparts of the jet knots N1 and M identified by VLBI observations.

Lauer, Tod R.↗

NASA NTRS1990

The 8 second optical quasi-periodic oscillations in GX 339 - 4

Submillisecond optical photometry of the black hole candidate GX 339 - 4 was obtained on August 1, 1989, (UT) using the 1.5 m telescope of the Cerro Tololo Inter-American Observatory. Eight second quasi-periodic oscillations of width 0.02-0.04 Hz and root mean square amplitude 4-6 percent are found. The visual magnitude of GX 339 - 4 at the beginning of the observation was m(v) = 17.7. Motch et al. (1985) have previously reported 7 s optical quasi-periodic oscillations when GX 339 - 4 was also m(v) = 17.7 and in an X-ray off-state. No X-ray observations were made during the present optical observations and so the X-ray state of GX 339 - 4 cannot be ascertained. In addition, Motch et al. have also reported 20 s optical quasi-periodic oscillations with 30-40 percent full amplitude but when GX 339 - 4 was much brighter, m(v) = 15.4, and in a hard X-ray state.

Imamura, James N.↗

NASA NTRS1989

The age of the LMC globular cluster NGC 1783

The age of the LMC red globular cluster NGC 1783 is estimated as 0.9 + or - 0.4 billion yr by photometry of the main-sequence turnoff. The accuracy of the estimate is limited chiefly by the uncertainty in the distance modulus of the cluster. At (m - M)0 = 18.2 the cluster is aged 1.1 + or - 0.2 Gyr; at (m - M)0 = 18.7 it is 0.7 + or - 0.2 Gyr. NGC 1783 is a sufficiently rich cluster that one can see the full development of red giants on the asymptotic giant branch from the M type, through S, to carbon-rich atmospheres.

Mould, Jeremy↗