Engineering topics

Patterson, J.

Publications and source records attributed to Patterson, J..

25 records · Page 2

NASA NTRS1983

The discovery of an X-ray bright BL Lacertae object - 0414 + 009

X-ray, optical, and radio observations have been made of an X-ray source originally discovered by Ulmer et al. (1980) in a survey of Abell clusters of galaxies. The relatively flat radio spectrum, the featureless optical spectrum, and the shape of the X-ray spectrum lead to the classification of the source as a BL Lacertae object. The source has one of the highest X-ray flux density ratios to both the optical and radio flux densities, and its strength at all these wavelengths warrants further multiwavelength studies. The radio, optical, and X-ray flux densities for the observations were 100 mJy, V = 16.4 (1 mJy), and 1 UFU (1.6 micro Jy). The X-ray flux varied by a factor of 2 over a 1 year period, but no 100 s time scale variations were seen. A search of the Harvard plate stacks did not reveal any optical variations. A model for the source is presented, and the implications of this object with respect to X-ray surveys are briefly discussed.

Brown, R. L.↗

NASA NTRS1983

Identification and properties of the M giant/X-ray system HD 154791 = 2A 1704+241

The Aerial V X-ray source 2A 1704+241 (= 4U 1700+24 = 3A 1703+241) is identified with the M3 II star HD 154791. The identification is based on a precise X-ray position determined by the HEAO 1 scanning modulation collimator and the Einstein Observatory imaging proportional counter, together with a spectrum measured by the International Ultraviolet Explorer. The ultraviolet spectrum shows strong emission of C IV 1550 A, N v 1238 A, and Mg II 2800 A, which is very unusual among M giants. This is the first X-ray detection of an M giant which has a completely normal optical spectrum. The X-ray luminosity reaches three orders of magnitude above the mean upper limit for the coronal X-ray flux from M giants. Although there is no direct evidence for a binary system, since radial velocity variations have not been observed, it is shown that a plausible neutron star binary model can be constructed.

Garcia, M.↗

NASA NTRS1983

Spin-up and magnetic fields in DQ Her stars

A detailed comparison of the spin-up behavior of the recently discovered faint long-period X-ray sources, using the accretion torque theory of Ghosh and Lamb has been carried out. It is confirmed that these sources are degenerate dwarfs. It is found that they have magnetic fields B about 1 billion G, an order of magnitude smaller than those of AM Her stars. On this basis, it is predicted that they will show significant polarization in the infrared.

Lamb, D. Q.↗

NASA NTRS1981

The amazing X-ray light curve of 2A 0311-227

The X-ray light curve of the AM Herculis-type binary 2A 0311-227 is presented. A smooth modulation of the X-ray flux at the orbital period is obtained, along with an eclipse feature that is total for 0.1-0.8 keV photons yet not visible for photons above about 3 keV. This strong and smooth dependence on energy suggests an origin in the obscuration of the X-ray emitting region by a column of accreting gas. Furthermore, very strong quasi-periodic pulsations with a period of about 6 min are found in the soft X-ray light curve. This periodicity is also present in the optical and hard X-ray light curves, and in the circular polarization data. It seems likely that the periodicity arises from a modulation of the mass accretion rate onto the white dwarf, and possible that it originates in pulsations of a disk-magnetosphere boundary.

Patterson, J.↗

NASA NTRS1981

Spectrophotometry of AM Herculis at minimum

Spectrophotometric observations of AM Her during its 1980 minimum are reported. The M dwarf in the system is revealed by its TiO bands and domination of the spectrum longward of 6000 A. The blue region of the spectrum reveals a hot, magnetic white dwarf with Zeeman-split hydrogen absorption lines, and emission lines of H, He I, and Fe II. The inferred surface magnetic field of roughly 10 to the 7th gauss permits the presence of an accretion disk in the system. Velocities and intensities of the H emission lines indicate an origin in the X-ray-heated atmosphere of the M dwarf. The continuum light variation in the red appears to result from the heating of the secondary, while the blue light variation probably results from the rotation of the bright spot at the white dwarf's magnetic pole. A self-consistent geometrical model is proposed, in which the minimum state is interpreted as a lull in the rate of accretion onto the white dwarf.

Patterson, J.↗

NASA NTRS1981

Rapid oscillations in cataclysmic variables. V - H2252-035, a single-sideband X-ray and optical pulsar

Photometric and spectroscopic observations of the optical counterpart of the X-ray source H2252-035 reveal the existence of stable periodicities of 3.59 hr and 14.31 min. Both radial velocity and photometric variations occur at the longer period, suggesting that it is the true orbital period of the underlying cataclysmic binary. The shorter period appears as a 10% modulation in the light curve, superposed on the 3.59 hr variation. The frequency is the lower orbital sideband of the X-ray pulsation frequency, suggesting that the optical pulses arise from reprocessing in the atmosphere of the secondary. Unlike the majority of X-ray pulsars, H2252-035 appears to contain a white dwarf rather than a neutron star.

Patterson, J.↗

NASA NTRS1980

33 second X-ray pulsations in AE Aquarii

The discovery of 33-s pulsations in the 0.1-4.0 keV light curve of the nova-like variable AE Aquarii is reported. These pulsations agree in period and phase with the optical pulsations. The periodicity probably originated from an accretion-induced hot spot on a rapidly rotating, magnetized white dwarf. It is possible that transient pulsations at nearby periods, similar to those seen in the optical light curve, are also present in the X-ray light curve.

Patterson, J.↗