A search for the Perseus flasher and the limits on optical burst rates

We conducted a study of the error box of the possible optical burster, reported by Katz et al. (1986). This “Perseus Flasher” was subsequently identified with satellite glints by Maley (1987), a conclusion with which we fully concur. Our study, completed before Maley’s report, involved a search for highly-variable objects on archival and newly-taken plates, with a total integration time of about 260 hours, a proper-motion survey of the area, deep optical imaging with a CCD, and a single-dish radio monitoring. We found no optical or radio bursts or any other unusual objects in this area. Our upper limit to the optical flash rate from the error box of the flash photographed by Katz et al. is at least 20 times lower than the flash rate reported by those authors. Similar negative results were achieved independently by other groups; like them, we conclude that the photographed flash was most likely caused by an Earth-orbiting artifact and that most of the remaining, visually-detected flashes were spurious. From our data, we derive limits on the optical flash rates from astrophysically-interesting sources

Astrometric Control of the Inertiality of the Hipparcos Catalog

Based on the most complete list of the results of an individual comparison of the proper motions for stars of various programs common to the Hipparcos catalog, each of which is an independent realization of the inertial reference frame with regard to stellar proper motions, we redetermined the vector $\omega$ of residual rotation of the ICRS system relative to the extragalactic reference frame. The equatorial components of this vector were found to be the following: $\omega_x = +0.04\pm 0.15$ mas yr$^{-1}$, $\omega_y = +0.18\pm 0.12$ mas yr$^{-1}$, and $\omega_z = -0.35\pm 0.09$ mas yr$^{-1}$.Comment: 8 pages, 1 figur

The investigation of absolute proper motions of the XPM Catalogue

The XPM-1.0 is the regular version of the XPM catalogue. In comparison with XPM the astrometric catalogue of about 280 millions stars covering entire sky from -90 to +90 degrees in declination and in the magnitude range 10^m<B<22^m is something improved. The general procedure steps were followed as for XPM, but some of them are now performed on a more sophisticated level. The XPM-1.0 catalogue contains star positions, proper motions, 2MASS and USNO photometry of about 280 millions of the sources. We present some investigations of the absolute proper motions of XPM-1.0 catalogue and also the important information for the users of the catalogue. Unlike previous version, the XPM-1.0 contains the proper motions over the whole sky without gaps. In the fields, which cover the zone of avoidance or which contain less than of 25 galaxies a quasi absolute calibration was performed. The proper motion errors are varying from 3 to 10 mas/yr, depending on a specific field. The zero-point of the absolute proper motion frame (the absolute calibration) was specified with more than 1 million galaxies from 2MASS and USNO-A2.0. The mean formal error of absolute calibration is less than 1 mas/yr.Comment: 11 pages, 9 figures, accepte

Optical Observations of the Binary Pulsar System PSR B1718-19: Implications for Tidal Circularization

We report on Keck and Hubble Space Telescope optical observations of the eclipsing binary pulsar system PSR B1718-19, in the direction of the globular cluster NGC 6342. These reveal a faint star ($m_{\rm F702W}=25.21\pm0.07$; Vega system) within the pulsar's 0\farcs5 radius positional error circle. This may be the companion. If it is a main-sequence star in the cluster, it has radius \rcomp\simeq0.3 \rsun, temperature \teff\simeq3600 K, and mass \mcomp\simeq0.3 \msun. In many formation models, however, the pulsar (spun up by accretion or newly formed) and its companion are initially in an eccentric orbit. If so, for tidal circularization to have produced the present-day highly circular orbit, a large stellar radius is required, i.e., the star must be bloated. Using constraints on the radius and temperature from the Roche and Hayashi limits, we infer from our observations that \rcomp\simlt0.44 \rsun and \teff\simgt3300 K. Even for the largest radii, the required efficiency of tidal dissipation is larger than expected for some prescriptions.Comment: 10 pages, 2 figures, aas4pp2.sty. Accepted for publication in Ap