Engineering topics

Cacciari, C.

Publications and source records attributed to Cacciari, C..

8 records

NASA NTRS1994

HST observations of globular clusters in M 31. 1: Surface photometry of 13 objects

We present the initial results of a study of globular clusters in M 31, using the Faint Object Camera (FOC) on the Hubble Space Telescope (HST). The sample of objects consists of 13 clusters spanning a range of properties. Three independent image deconvolution techniques were used in order to compensate for the optical problems of the HST, leading to mutually fully consistent results. We present detailed tests and comparisons to determine the reliability and limits of these deconvolution methods, and conclude that high-quality surface photometry of M 31 globulars is possible with the HST data. Surface brightness profiles have been extracted, and core radii, half-light radii, and central surface brightness values have been measured for all of the clusters in the sample. Their comparison with the values from ground-based observations indicates the later to be systematically and strongly biased by the seeing effects, as it may be expected. A comparison of the structural parameters with those of the Galactic globulars shows that the structural properties of the M 31 globulars are very similar to those of their Galactic counterparts. A candidate for a post-core-collapse cluster, Bo 343 = G 105, has been already identified from these data; this is the first such detection in the M 31 globular cluster system.

Pecci, F. Fusi↗

NASA NTRS1993

The first detection of a collapsed core globular cluster in M31

We report on the observations of a globular cluster (designated G105 = Bo 343) in the nearby spiral galaxy M31, using the Hubble Space Telescope (HST). Image deconvolutions using three different methods indicate that this cluster has a density profile with the morphology characteristic of stellar systems which have undergone core collapse, i.e., a power-law density cusp near the center. This is the first such detection in a galaxy as distant as M31. This discovery may lead to extensive future statistical studies of the globular cluster system of M31, and thus a better understanding of its evolution.

Bendinelli, O.↗

NASA NTRS1991

A line identification study of the IUE SWP high dispersion spectrum of the UV-bright star Barnard 29 of Messier 13

A line identification study was performed of the coaddition of three SWP high dispersion IUE exposures of the UV-bright star Barnard 29 of Messier 13. One of these images took two IUE shifts. The previous study by de Boer and Savage (1983) was extended and stellar lines of C I, C II, C III, C IV, N I, N III, O I, O III, O IV,Al III, Si II, Si III, Si IV, P III, S II, and S III and interstellar lines of C I, C II, C IV, N I, N III, N IV, N V, O I, Al II, Al III, Si II, Si IV, S II, and Fe II were found. These lines are the strongest expected lines in a hot Population II star. Apparent intensity minima corresponding to interstellar features are noted, especially those matching a high velocity cloud found by de Boer and Savage.

Adelman, S. J.↗

NASA NTRS1989

The Baade-Wesselink method applied to field RR Lyrae stars. II - SW Andromedae, SW Draconis, and SS Fornacis

The Baade-Wesselink method has been combined with previous photometry and radial velocities to yield distances of 520 + or - 50 pc, 840 + or - 50 pc, and 780 + or - 150 pc, and mean absolute magnitudes of 0.88 + or - 0.20, 0.86 + or - 0.20, and 0.73 + or - 0.50, for SW And, SW Dra, and SS For, respectively. The present technique is able to account for the problem of phase-lag between spectroscopically and photometrically determined radial displacements in SW Dra, the Blazhko effect in SW And, and both the phase-lag and Blazhko effects in SS For.

Cacciari, C.↗

NASA NTRS1989

The Baade-Wesselink method applied to field RR Lyrae stars. III - YZ Capricorni, RV Phoenicis, and V440 Sagittarii

Application of the Baade-Wesselink method to three field RR Lyrae variables reveals evidence of shock waves in the atmospheres of RV Phe and V440 Sgr (but not YZ Cap) during maximum light. The results yield distance moduli of 24.21 + or - 0.20 for M31, 18.26 + or - 0.20 for the LMC, and 18.85 + or - 0.20 for the SMC. Using the Sandage (1982) age/turn-off luminosity relationship of VandenBerg and Bell (1985), estimated ages of 18.8 Gyr for M92 and of 15.7 Gyr for 47 Tuc are derived.

Cacciari, C.↗

NASA NTRS1982

The UV stellar classification program

The UV stellar classification program based on IUE data, its rationale, and its status, are described. The program provides sequences of calibrated spectra covering all spectral types.

Heck, A.↗

NASA NTRS1982

Coordinated observations of Seyfert I galaxies

A program to obtain simultaneous observations from the X-ray to the IR of Seyfert I galaxies is outlines. Of particular interest is the variability of these Seyfert nuclei. The continuum flux distribution in the UV for AkN 120 and ESO 113-IG45 (F-9) is examined.

Wamsteker, W.↗

NASA NTRS1982

The ultraviolet variability of T Cr B

Preliminary results of the ultraviolet variability monitoring of the recurrent nova T Cr B are presented. The star has shown striking changes of the continuum (both shape and integrated luminosity) and of the emission lines since 1979, with a maximum activity in early 1981. In the same period the visual luminosity remained practically constant. The data being studied that the UV variability is due to changes in the physical structure of the accretion disk around the secondary.

Cassatella, A.↗