High Speed photometry of faint Cataclysmic Variables: I. V359 Cen, XZ Eri, HY Lup, V351 Pup, V630 Sgr, YY Tel, CQ Vel, CE-315

The first results of a photometric survey of faint Cataclysmic Variables are presented. V359 Cen is an SU UMa star with a period of 112 min. Even though observed at quiescence, the mass transfer rate in this old nova may be sufficiently high that in such a short period system (with its implied small mass ratio) the disc may be excited into an elliptical shape with the result that the observed brightness modulation gives a superhump period rather than an orbital period. XZ Eri is an eclipsing dwarf nova with an orbital period (P(orb)) of 88.1 min. HY Lup has only slight variability. V351 Pup, the remnant of Nova Puppis 1991, has P(orb) = 2.837 h and a light curve that strongly resembles that of the magnetic Nova Cyg 1975. V630 Sgr is the first nova remnant that has both positive superhumps (P(sh) = 2.980 h) and eclipses (P(orb) = 2.831 h). The YY Tel identification is somewhat uncertain. The correct identification for CQ Vel is provided from discovery of its flickering activity. The light curve of CE-315, a recently discovered AM CVn star, shows similarities to that of GP Com, with no apparent orbital modulation.Comment: 8 pages, 12 figures, accepted for publication in MNRA

Measurement of Pressures by Cardiac Catheters in Man

journal articleBiomedical Informatic

Measurement of Pressures in Man by Cardiac Catheters

journal articleBiomedical Informatic

Eclipse studies of the dwarf-nova Ex Draconis

We report on high speed photometry of EX Dra in quiescence and in outburst. The analysis of the lightcurves indicates that the outbursts do not start in the outer disc regions. The disc expands during rise to maximum and shrinks during decline and along the quiescent period. At the end of two outbursts the system was seen to go through a phase of lower brightness, characterized by an out-of-eclipse level ~15 per cent lower than the typical quiescent level and by the fairly symmetric eclipse of a compact source at disc centre with little evidence of a bright spot at disc rim. New eclipse timings were measured and a revised ephemeris was derived. The residuals with respect to the linear ephemeris are well described by a sinusoid of amplitude 1.2 minutes and period \~4 years and are possibly related to a solar-like magnetic activity cycle in the secondary star. Eclipse phases of the compact central source and of the bright spot were used to derive the geometry of the binary. By constraining the gas stream trajectory to pass through the observed position of the bright spot we find q=0.72+/-0.06 and i= 85 +3/-2 degrees. The binary parameters were estimated by combining the measured mass ratio with the assumption that the secondary star obeys an empirical main sequence mass-radius relation. We find M_1= 0.75+/-0.15 M_sun and M_2= 0.54+/-0.10 M_sun. The white dwarf at disc centre is surrounded by an extended and variable atmosphere or boundary layer of at least 3 times its radius and a temperature of T ~28000 K. The fluxes at mid-eclipse yield an upper limit to the contribution of the secondary star and lead to a lower limit photometric parallax distance of D= 290+/-80 pc. The fluxes of the secondary star are well matched by those of a M0+/-2 main sequence star.Comment: submitted to MNRAS, 12 pages, 9 figures; coded with MNRAS latex styl

Inadequate income as a factor forcing married women into gainful occupations

This item was digitized by the Internet Archive. Thesis (M.A.)--Boston Universityhttps://archive.org/details/inadequateincome00woo

WZ Sagittae as a DQ Herculis star

We argue that quiescent WZ Sge is a rapidly spinning magnetic rotator in which most of the matter transfered from the secondary is ejected from the system. Assuming that the observed 27.87 s oscillation period is due to the spinning white dwarf we propose that the other observed principal period of 28.96 s is a beat due to reprocessing of the rotating white dwarf beam on plasma blobs in Keplerian rotation at the outer disc rim. The weaker, transient, 29.69 s period is identified as a beat with the Keplerian period of the magnetosphere. WZ Sge evolves through a cycle of spin-up and spin-down phases. During the spin-down phase it is a DQ Her star, during the spin-up phase it should be a ER UMa star.Comment: 8 pages, 5 figures; accepted for publication in MNRA

Evidence for the White Dwarf Nature of Mira B

The nature of the accreting companion to Mira --- the prototypical pulsating asymptotic giant branch star --- has been a matter of debate for more than 25 years. Here we use a quantitative analysis of the rapid optical brightness variations from this companion, Mira B, which we observed with the Nickel telescope at Lick Observatory, to show that it is a white dwarf (WD). The amplitude of aperiodic optical variations on time scales of minutes to tens of minutes (approximately 0.2 mag) is consistent with that of accreting WDs in cataclysmic variables on these same time scales. It is significantly greater than that expected from an accreting main-sequence star. With Mira B identified as a WD, its ultraviolet (UV) and optical luminosities, along with constraints on the WD effective temperature from the UV, indicate that it accretes at ~1e-10 solar masses per year. We do not find any evidence that the accretion rate is higher than predicted by Bondi-Hoyle theory. The accretion rate is high enough, however, to explain the weak X-ray emission, since the accretion-disk boundary layer around a low-mass WD accreting at this rate is likely to be optically thick and therefore to emit primarily in the far or extreme UV. Furthermore, the finding that Mira B is a WD means that it has experienced, and will continue to experience nova explosions, roughly every million years. It also highlights the similarity between Mira AB and other jet-producing symbiotic binaries such as R Aquarii, CH Cygni, and MWC 560, and therefore raises the possibility that Mira B launched the recently discovered bipolar streams from this system.Comment: Accepted for publication in Ap

The use of a small mobile X-ray generator and contrast techniques for the radiographic examination of the canine thorax.

The increasing awareness of the public concerning aids to diagnosis, and the increasing affluence of the small animal owner has made radiography an essential adjunct to veterinary practice

The Kepler Light Curve of V344 Lyrae: Constraining the Thermal-Viscous Limit Cycle Instability

We present time dependent modeling based on the accretion disk limit cycle model for a 270 d light curve of the short period SU UMa-type dwarf nova V344 Lyr taken by Kepler. The unprecedented precision and cadence (1 minute) far surpass that generally available for long term light curves. The data encompass two superoutbursts and 17 normal (i.e., short) outbursts. The main decay of the superoutbursts is nearly perfectly exponential, decaying at a rate ~12 d/mag, while the much more rapid decays of the normal outbursts exhibit a faster-than-exponential shape. Our modeling using the basic accretion disk limit cycle can produce the main features of the V344 Lyr light curve, including the peak outburst brightness. Nevertheless there are obvious deficiencies in our model light curves: (1) The rise times we calculate, both for the normal and superoutbursts, are too fast. (2) The superoutbursts are too short. (3) The shoulders on the rise to superoutburst have more structure than the shoulder in the observed superoutburst and are too slow, comprising about a third to half of the total viscous plateau, rather than the ~10% observed. However, one of the alpha_{cold} -> alpha_{hot} interpolation schemes we investigate (one that is physically motivated) does yield longer superoutbursts with suitably short, less structured shoulders.Comment: 39 pages, 9 figures, accepted in the Astrophysical Journa