Mitchell F. Struble

A Compilation of Redshifts and Velocity Dispersions for ACO Clusters

We present a compilation of redshifts for 1572 Abell, Corwin, & Olowin (ACO) clusters, referenced to both the heliocentric and cosmic background radiation reference frames, and 395 velocity dispersions corrected to the reference frame of the cluster, available from the literature as of 1998 December. We present an additional list of 81 ACO clusters with published redshifts which are probably those of galaxies or groups superimposed on, or near, the ACO cluster position.

A compilation of redshifts and velocity dispersions for Abell clusters (epoch 1991.2)

A list of redshifts for 758 Abell clusters, and velocity dispersions for 121, published as of 1991 March, and another list of 33 Abell clusters with published redshifts, most of which are probably redshifts of foreground or background galaxies superposed on, or near, the Abell clusters, are presented. Over the past 4 years, the published number of redshifts of member galaxies in clusters increased by a factor of 2.0, but the number of cluster redshifts increased by only a factor of 1.3, while the number of cluster velocity dispersions derived from 50 or more redshifts of member galaxies increased by a factor of 3.8 (from 6 to 23)

Finding outlier light curves in catalogues of periodic variable stars

We present a methodology to discover outliers in catalogues of periodic light curves. We use a cross-correlation as the measure of ‘similarity’ between two individual light curves, and then classify light curves with lowest average ‘similarity’ as outliers. We performed the analysis on catalogues of periodic variable stars of known type from the MACHO and OGLE projects. This analysis was carried out in Fourier space and we established that our method correctly identifies light curves that do not belong to those catalogues as outliers. We show how an approximation to this method, carried out in real space, can scale to large data sets that will be available in the near future such as those anticipated from the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) and Large Synoptic Survey Telescope (LSST).

SPATIAL COINCIDENCE BETWEEN A NUMBER OF HICKSON COMPACT GROUPS AND LOOSE GROUPS OR CLUSTERS

Spatial coincidences have been detected between Hickson compact groups and 36 loose groups and seven Abell clusters. The coincidences were found from examination of (a) prints of the Palomar Sky Survey, (b) galaxy redshift information in the de Vaucouleurs et al. (1992) Third Reference Catalog of Bright Galaxies, (c) locational information for loose groups in recent catalogs by Fouque et al. (1992), Nolthenius (1993), Garcia (1993) and (d) locational information for Abell clusters. Seven-tenths (0.7) of the Hickson compact groups with redshift z

Superposition and incompleteness effects in Abell's statistical sample of clusters

Data in the Morphological Catalog indicate that visually detectable foreground/background clusters are superposed on ∼3% of the 1682 clusters of Abells 1958 statistical sample. Galaxy redshift histograms of 43 clusters in the statistical sample within distance classes D ≤ 4 and with at least 10 known galaxy redshifts indicate that a superposed aggregate has lifted 5%, that is, only two clusters, from the nonstatistical sample into the statistical sample at the 2 σ level, but none at the 3 σ level. No superposed aggregates rich enough to be called Abell clusters in D ≤ 4 are found, but several are identified with redshifts corresponding to D = 5 and 6

Gamma-Ray Bursts from Rich Concentrated Abell-Corwin-Olowin Clusters: The Luminosity-Duration Relation

A likelihood statistic constructed from positions and positional uncertainties identifies 82 associations of BATSE sources with rich, concentrated Abell clusters. Random simulations indicate that 42 ± 9 of these pairs are chance associations. Among the approximately 40 physically associated cluster-gamma-ray burst (GRB) pairs (the nearest containing the Coma Cluster and GRB 2193), we find (1) a plateau between 15.8 and 16.2 mag in the integral (observed-minus-random) number distribution of mR(10), the magnitude of 10th brightest cluster member, which may indicate the presence of two burst populations with different characterstic intrinsic luminosities; (2) the dispersion in GRB fluences between 100 and 300 keV (represented as apparent magnitude, m[100-300 keV]) is smaller for bursts paired with mR(10) ≤ 16.2 clusters than for those with mR(10) > 16.2; (3) the average 100-300 keV isotropic intrinsic energy of GRBs associated with mR(10) ≤ 16.2 clusters with known redshift z 99.9% confidence level). The slope of this relation indicates t90∝L−11024. These results suggest that the anticorrelation of apparent burst magnitude with duration is an intrinsic property of the bursts and is not caused by cosmological time dilation.

Can red shifts turn blue

Red shifts can turn blue and blue shifts can turn red in real astrophysical situations involving magnetic neutron stars. It is also possible for red shifts and blue shifts to be emitted simultaneously from the same object. With this general relativistic effect, the red shift may be arbitrarily large but the blue shift cannot exceed 1/2.

Red and blue shifts near compact objects

We show that radiation emitted from material falling toward a black hole or neutron star can be blue-shifted as well as red-shifted. Although the red shift can be arbitrarily large near a black hole, there is an upper limit for the blue shift of 1/2. Material incident toward the poles of a magnetic neutron star can simultaneously radiate red and blue-shifted lines. Near an oblique magnetic rotator, the red and blue shifts will show a sinusoidal variation. Such spectral variations are associated with SS 433.

Hydrogen spectrum of SS433 system

We propose that the hydrogen spectrum in intense magnetic fields will help clarify the mechanisms which govern the SS433 system. In ultra high magnetic fields the standard hydrogen spectrum is superimposed on the Landau levels. There is, however, one deep-lying level in hydrogen at an energy of 50 eV to greater than 200 eV, depending on the magnetic field strength typical of neutron stars in x-ray binaries. When this level manifests itself it will give an indication of the magnetic field strength at the location of the radiating material; it could thus support the infall model SS433.

Observable blueshifts near compact objects

We show that observable blueshifted radiation can emanate from material freely falling toward compact objects. Using a fully relativistic treatment and considering possible blocking of photon trajectories by a neutron star or black hole, we demonstrate that blueshifts are observable.