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A correlation between the incidence of influenza pandemics and increased cosmic ray activity is made. A correlation is also made between the occurrence of these pandemics and the appearance of bright novae, e.g., Nova Eta Car. Four indices based on increased cosmic ray activity and novae are proposed to predict future influenza pandemics and viral antigenic shifts.
Attention is given to the stability and evolution of some simple accretion disk models in which the viscosity is prescribed by an ad hoc, uniform-alpha model. Emphasis is placed on systems in which the mass input rate from the secondary to the disk around the primary is assumed to be constant, although initial calculations with variable mass input rates are also performed. Time-dependent visual magnitude light curves constructed for cataclysmic binaries with a range of disk size, primary mass and mass input rate, and viscosity magnitude, are compared with the observed properties of various cataclysmic variable subclasses. The results obtained indicate that the observational differences between novae and dwarf novae may be due to mass input rate differences. The present models can reproduce the gross observational features of U-Gem-type dwarf nova outbursts.
Papers are presented on the formation and evolution of low-mass close binaries with compact components, the periods of cataclysmic variables, multiwavelength observations of dwarf novae during outbursts, and radio emission from cataclysmic variables. Also considered are long-term optical photometry of the dwarf nova VW Hyi, periodic modulations in the optical light curves of EX Hydrae, and Echelle-Mepsicron time-resolved spectroscopy of the dwarf nova SS Cygni. Other topics include UV and X-ray observations of cataclysmic variables, new EXOSAT observations of TV Columbae, accretion disk evolution, and the boundary layer in cataclysmic variables.
Additional photometric observations of an unusual red nova that appeared in M31 in 1988 are presented. It was shown by means of mV observations that the nova is a very red object, in agreement with observations presented by Rich et al. (1989) and Mould et al. (1990). The nova was found to fall well off the maximum magnitude versus rate of decline relationship shown in Rosino (1964) and van den Bergh (1988).
The Hubble Space Telescope with its UV and imaging capabilities will allow new methods of investigating cataclysmic variables to be used. It provides the first opportunity to obtain high-time-resolution UV observations of cataclysmic variables, both spectroscopically and photometrically. Phase-resolved observations of eclipses can now be obtained which will allow the UV surface-brightness distributions in accretion disks to be studied. Eclipses of white dwarfs that were not visible in optical light will be detected in some systems. Other variations such as dips (in dwarf novae, intermediate polars, and polars), flickering, and oscillations can also be resolved for the first time in the UV. High-spatial-resolution, long-slit spectroscopy, and imaging with the FOC and WF/PC can be used to study the physical condition and morphology of ejected material around novae, recurrent novae, and precataclysmic variables. The UV and H-alpha imaging capabilities will also enable searches for cataclysmic variables in globular clusters to be carried out further into their cores than has been possible before.
The results are reported of an extensive 1991 campaign to determine an accurate value of the period of the old nova V603 Aquilae, free from aliasing, in at least one season. Phase drift of +/- 0.3 cycles around the mean period is present on a time scale of about six months. The period is shown to be unstable. There is an interesting resemblance of the 0.146 day photometric signal to the 'superhumps' of dwarf novae. However, the light variations are irregular and not similar to those of dwarf novae. The relationship between observed orbital and superhump period is studied, and it is predicted that V603 Aql is the first of many noneruptive cataclysmic variables which will be recognized as showing superhumps.
LMC 1988 #1 was a slow, CO type, dust forming classical nova. It was the first extragalactic nova to be observed with the IUE satellite. We have successfully fitted observed ultraviolet and optical spectra of LMC 1988 #1 taken within the first two months of its outburst (when the atmosphere was still optically thick) with synthetic spectra computed using PHOENIX nova model atmospheres. The synthetic spectra reproduce most of the features seen in the spectra and provide V band magnitudes consistent with the observed light curve. The fits are improved by increasing the CNO abundances to 10 times the solar values. The bolometric luminosity of LMC 1988 #1 was approximately constant at 2 x 10(exp 38) ergs per second at a distance of 47.3 kpc for the first 2 months of the outburst until the formation of the dust shell.
Topics include: Fermi LAT Collaboration groups; galactic results from LAT; a GeV, wide-field instrument; the 1FGL catalog, the Fermi LAT 1FGL source catalog, unidentified gamma-ray sources; variability in 1FGL sources; curvature in 1FGL sources; spectral-variability classification; pulsars and their wind nebulae; gamma-ray pulsars and MSPs; GeV PWN search; Crab pulsar and nebula; Vela X nebular of Vela pulsar; MSH 15-52; supernova remnants, resolved GeV sources, galactic transients, LAT unassociated transient detections; gamma rays from a nova; V407 Cyngi - a symbiotic nova; V407 Cygni: a variable star; and March 11 - a nova. Summary slides include pulsars everywhere, blazars, LAT as an electron detector, cosmic ray spectrum, the Large Area Telescope, the Fermi Observatory, LAT sensitivity with time, candidate gamma-ray events, on-orbit energy calibration and rate, a 1 year sky map, LAT automated science processing, reported GeV flares, early activity and spectacular flare, gamma-ray transients near the galactic plane , two early unassociated transients, counter part search - Fermi J0910-5404; counterpart search 3EG J0903-3531, and a new LAT transient - J1057-6027.
During the rocket-powered landing of a vehicle on a planetary body, the interaction between the rocket plume and the surface material beneath the vehicle plays a significant role in the descent dynamics and the safety of powered descent. However, in-situ data taken to investigate plume-surface interaction has been limited. The upcoming flight and lunar landing of the Intuitive Machines Nova-C will be equipped with the Stereo Cameras for Lunar Plume-Surface Studies (SCALPSS) science package, enabling the direct measurement of plume-induced surface cratering during powered descent. In this work, we present the engineering constraints, design iteration process, and simulation results that drove the design selection for the SCALPSS camera system. The chosen design will provide 3D-imaging coverage of 84 percent of the lunar surface directly under the landed Nova-C, in addition to some coverage of the neighboring surface. SCALPSS will provide a total 3D-imaging coverage area of approximately 13 square meters. With the anticipated Nova-C landing in October of 2021, SCALPSS will provide the first dedicated in-situ measurement of plume-induced surface cratering.
Numerical sequences of rotating axisymmetric nonmagnetic equilibrium models are constructed which represent the evolution of a barytropic star as it accretes material from a rotating medium. Two accretion geometries are considered - one approximating accretion from a rotating cloud and the other, accretion from a Keplerian disk. It is assumed that some process, such as Ekman spin-up or nonequilibrium oscillations, maintains nearly constant angular velocity along cylinders about the rotation axis. Transport of angular momentum in the cylindrically radial direction by viscosity is included. Fluid instabilities and other physical processes leading to enhancement of this transport are discussed. Particular application is made to zero-temperature white-dwarf models, using the degenerate electron equation of state. An initially nonrotating 0.566-solar-mass white dwarf is followed during the accretion of more than one solar mass of material. Applications to degenerate stellar cores, to mass-transfer binary systems containing white dwarfs, such as novae and dwarf novae, to Type I supernovae, and to galactic X-ray sources are considered.
Results are reported for HEAO A2 soft X-ray (below 2 keV) scanning observations of the southern dwarf nova EX Hya. An X-ray light curve is presented which shows no apparent orbital modulation. The best-fitting spectral parameters are derived for the source, and the observations are compared with the spectral behavior of the dwarf nova SS Cyg during optical quiescence. The results are discussed in terms of models for X-ray production by accreting white dwarfs.
The weak hard X-ray source 2A 0526-328 is identified with a previously unknown cataclysmic variable on the basis of its optical emission-line spectrum and a precise X-ray location. This star has a V magnitude of about 11 and spectral properties similar to dwarf novae at minimum light and AM Her, but shows no polarization. It is likely to be a Z Camelopardalis-type system in a very extended standstill (i.e., 'novalike' or UX Ursae Majoris-type) or a recurrent nova that has not erupted in recent times.
Pulsed soft X-rays (0.1 to 0.5 keV) with a period of 9 sec and a pulsed fraction that varies between 0 and 100% were detected from the dwarf nova SS Cygni at the peak of an optical outburst. This detection confirms for the first time the supposed high energy origin of optical pulsations seen in erupting dwarf novae. The pulse shape is remarkably sinusoidal for such a large-amplitude oscillation. The X-ray pulsation observed in this outburst is not coherent, in contrast to previous claims for the related optical oscillations.
Preliminary results of the analysis of the low resolution spectra from the recurring nova WZ Sagittae are discussed with reference to the similarity between WZ Sge and dwarf novae and the applicability of accretion disk models. It is found that the spectrum observed on Dec. 1, 1978, is in very good agreement with a simple steady-state disk model of Lynden-Bell (1969) which predicts a power law spectrum over a limited range of frequency. Analysis of the observations within the framework of this model gives a value of the mass of the white dwarf larger than that estimated by Robinson et al (1978).
High-speed photometric observations of the dwarf nova SS Cygni have been made using an ultraviolet and blue sensitive photomultiplier. Rapid oscillations were detected over an interval of 7 days. The period of the oscillations passed through a minimum of 7.29 s, the shortest period yet observed in a dwarf nova. The signal was spread in frequency by an amount larger than required by the slow evolution of the period. The data are considered from the viewpoint of several models.
A low-resolution IUE spectrum (1200 A-1900 A) of the twin-degenerate white-dwarf binary star G61-29 is presented. A comparison is made to similar IUE spectra of the old novae DQ Her and V603 Aql. G61-29 shows N V 1240 A and He II 1640 A in emission. Unlike the old novae, the C IV 1550 A doublet is not present. It is proposed that the mass-losing He white dwarf (with a mass of 0.02 solar mass) is the H-exhausted, He-rich core of an old star in which the original CNO nuclei have been converted to N-14 by the CNO-cycles.
During the HEAO 1 satellite's detection of soft X-ray pulsations from U Geminorum and SS Cygni, both of these dwarf novae were on the declining phase of an optical outburst. The pulsations are quasi-coherent in character, with average pulse amplitudes of 15 percent for U Gem and 18 percent for SS Cyg. From pulse phase X-ray spectroscopic data, an upper limit of 50 percent may be set on any variation in temperature across U Gem's pulse. Attention is given to all data on the X-ray and optical pulsations thus far detected in these two novae, and the observational constraints on the various current models for the pulsations are discussed.
The amount of dispersed interstellar Al-26 detected by the HEAO 3 gamma-ray spectrometer cannot have been synthesized by supernova explosions if current calculations of the production ratio p(26)/p(27) approximately equal to 0.001 are correct. Simple models of chemical evolution of the Galaxy are presented to explain this point. The observed Al-26 is more likely due to about 100 million dispersed novae, or to a single old (10,000-1,000,000 yr) supernova remnant that today surrounds the solar system. If the Al-26 is dispersed, the high interstellar ratio today Al-26/Al-27 about equal to 0.00002 calls into question the requirement that a supernova trigger for formation of the solar system was the cause of a concentration 3-times larger. Also discussed is p-process production in novae with application to the question of live Sm-146 in the solar system.