X-ray photometry of M1
M1 X ray emission, examining energy interval and power law spectral distribution
Acton, L. W.↗
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Photometry of slow X-ray pulsars. II - The 13.9 minute period of X Persei
Results are presented for time-resolved narrow-band photometry and spectrophotometry of X Per performed in an unsuccessful effort to confirm previously reported observations of 13.9-min pulsations in the intensity of the He II line at 4686 A. No features that are synchronous with a 13.9-min period are found in the optical data, and simultaneous X-ray observations of 3U 0352+30 are reported which show that a strong 13.9-min X-ray modulation was present during the optical photometry. Some implications of the X-ray periodicities observed for X Per are considered.
Margon, B.↗
Effect of weightlessness on mineral saturation of bone tissue
X-ray photometry of bone density established dynamic changes in mineral saturation of bone tissues for Soyuz spacecraft and Salyut orbital station crews. Calcaneus optical bone densities in all crew members fell below initial values; an increase in spacecrew exposure time to weightlessness conditions also increased the degree of decalcification. Demineralization under weightlessness conditions took place at a higher rate than under hypodynamia.
Krasnykh, I. G.↗
Photometry of slow X-ray pulsars. III - The GX 17 + 2 candidate
The optical pulsations from the faint star assumed to be the optical counterpart of the intense X-ray source GX 17 + 2 are analyzed. The X-ray source is of interest because of its associated radio emission, and the 1913 sec periodic modulation of the X-ray flux, which makes the source the slowest X-ray pulsar yet observed. The photoelectric photometry of the star provides no evidence for variability. The analysis indicates that any binary period in GX 17 + 2 is most likely longer than two days.
Margon, B.↗
Optical observations of Sanduleak 160.
The variability of Sanduleak 160, the proposed optical counterpart of SMC X-1, has been confirmed. It shows a double-peaked optical variation with the minimum at X-ray eclipse being the deeper. The cos 2 theta variation has a semiamplitude of 0.050 mag in the B filter, the cos theta variation has a semiamplitude of 0.025 mag, and there is a cos 3 theta variation of 0.012 mag semiamplitude. From an analysis of the optical photometry and X-ray eclipse duration the mass ratio is found to be 0.28, i = 79 deg, and P = 3.89206 days. On the assumption that the mass of Sk 160 is 20 solar masses, the mass of SMC X-1 is 5.6 solar masses.
Petro, L.↗
K/rb ratios in tektites.
Potassium/rubidium ratios and individual K and Rb contents for 54 tektites determined by flame photometry or X-ray fluorescence
TEKTITE↗
Photometry of AM Herculis - A slow optical pulsar
Multicolor photometry of the X-ray binary AM Her suggests that the red component of the optical flux is closely related to the source of optical circular polarization in the system. It is concluded from the periodic modulation of flux in the U through R bands, which is particularly well-defined when plotted as color curves, that the primary and secondary minima are neither eclipses by a secondary star nor eclipses by a hot spot. It is suggested that the primary minimum in the visual light curve is the eclipse of a region of intense optical emission in the magnetic field near the surface of a degenerate dwarf by that dwarf itself.
Priedhorsky, W. C.↗
An X-ray survey of BL Lacertae objects
Results are reported for X-ray observations and nearly simultaneous photographic photometry of four BL Lacertae objects (BL Lac, W Com, ON 325, and AP Lib). The X-ray data were obtained in the band from 2.5 to 7.5 keV using a collimated proportional counter aboard OAO-C. Although none of the sources was detected above background at a statistically significant level, two-sigma upper limits on the X-ray flux incident at earth are given for each object. The photometric data indicate that all four objects were near the faint end of their visibility ranges during the time of the X-ray observations. The X-ray upper limits and B magnitudes are employed to calculate upper limits on the brightness temperatures and angular sizes of the radio synchrotron sources; upper limits on the distances to the objects are obtained from limits on the physical source sizes deduced from the radio variabilities. The strictest distance limit is 240 Mpc for BL Lac. Substantial evidence is noted for variability of ON 325 on a timescale of hours.
Margon, B.↗
OBSERVATIONS OF THE VAN ALLEN RADIATION REGIONS DURING AUGUST AND SEPTEMBER 1959 5. VISUAL AURORAS, HIGH-ALTITUDE X-RAY BURSTS, AND SIMULTANEOUS SATELLITE OBSERVATIONS
Correlation of variations of explorer vi count rates with simultaneous visual auroras and high- altitude x-ray bursts
EXPLORER VI SATELLITE↗
On the optical identification of Sco X-1.
Optical identification of position of X-ray astronomical source Sco X-1, noting similarity of certain properties with old novae
X-RAY ASTRONOMY↗
He II lambda 4686 photometry of HD 153919
The optical component of the binary X-ray source 3U1700-37/HD 153919 was observed with the interference filter centered on the He II lambda 4686 emission. This photometry does not reveal any dependence of lambda 4686 emission on the orbital phase thereby confirming earlier spectroscopic result that the region of formation of the ionized helium emission is confined to the envelope of the 06f primary.
Krzeminski, W.↗
Simultaneous photometry of X Persei and 3U 0352+30
The suggested association of X Persei with the weak X-ray source 3U 0352+30 raises the possibility of detection of X-ray/optical covariability. The paper reports a successfully conducted simultaneous optical/X-ray observation utilizing ground-based photometry and a satellite-borne proportional counter. Photoelectric photometry of X Persei was obtained on five out of seven consecutive nights in January 1975. The observations yield the faintest and bluest photoelectric magnitudes and colors ever reported for X Per; this change apparently occurred relatively uniformly during 1973-74 and is reminiscent of behavior last observed in about 1900. On January 21, 7 hr of data were obtained simultaneously with OAO Copernicus X-ray observations of 3U 0352+30. The X-ray flux varied during this period by a factor of 2, but there is no obviously correspondent optical activity, to a level of 0.02 mag. The optical data are also used to limit the 0.01-mag variations coincident with the X-ray periodicity reported by White et al. (1976).
Margon, B.↗
Optical candidates for two X-ray bursters and an X-ray pulsar
Faint blue stars are suggested as the optical counterparts of the X-ray bursters 4U (MXB) 1636-53 and 4U (MXB) 1735-44 as well as the 7-sec X-ray pulsar 4U 1626-67. The candidate stars have large UV excesses and were discovered well within the 20- and 30-arcsec error radii determined with the rotating modulation collimator aboard SAS 3. Photographic observations and photoelectric photometry of the candidate stars are discussed. It is shown that the candidates for 4U 1626-67 and 4U 1636-53 lie further from the reddened-supergiant or main sequence than any known X-ray source counterparts and have colors that are inconsistent with those of a reddened normal star, while the candidate for 4U 1735-44 has the colors of both Sco X-1 and a late O or BO star suffering about 1 mag of extinction.
Mcclintock, J. E.↗
Scientific investigations on the Skylab satellite; Conference, Huntsville, Ala., October 30-November 1, 1974, Technical Papers
A Skylab overview is presented and the solar observation programs are examined, taking into account the operational aspects of Skylab, the XUV sun as observed by ATM S082, a classification of flares and flarelike events observed during the Skylab mission, a preliminary analysis of extreme ultraviolet and X-ray observations, and initial results from the EUV spectroheliometer on ATM. Attention is given to ultraviolet stellar spectra obtained with Skylab experiment S019, multicolor photometry of low-light level phenomena from Skylab, Skylab observations of comet Kohoutek, relativistic iron in space and its nuclear progeny, Skylab altimeter applications and scientific results, neutron and proton activation measurements from Skylab, Skylab D024 thermal control coatings and polymeric films experiment, the stability of liquid dispersions in low gravity, observations of the liquid/solid interface in low-gravity melting, and student experiments on Skylab. Individual items are announced in this issue and in issue 02, 1975.
Kent, M. I.↗
The optical counterpart of Aquila X-1 /3U 1908+00/
We have discovered a highly variable star very close to the center of the SAS 3 error circle for the flaring X-ray source Aquila X-1 (3U 1908+00). Photographic photometry over the last 4 years shows covariability; the optical counterpart brightens from B greater than 20 to B approximately 17 mag during times of X-ray outburst, thus establishing the identification. Spectrophotometry of this star during its quiescent state shows spectral features of a K0 star with no obvious peculiarities; its distance must be at least 1.7 kpc.
Thorstensen, J.↗
The nature of the X-ray nova A0620-00
A model is presented for the X-ray nova A0620-00. Identification with a nova can be ruled out on two counts. A binary consisting of a late-type subgiant near the Roche lobe, irradiated by an accreting compact companion is shown, however, to be in agreement with all known observations. Photometry of the optical object should be pursued since variability on an approximately eight hour period is expected.
Endal, A. S.↗
Extreme-ultraviolet observations of dwarf novae from Apollo-Soyuz
The paper reports on EUV observations of four dwarf novae (SS Cyg, Z Cha, VW Hyi, and AE Aqr) in July 1975 during the Apollo-Soyuz Test Project, which were performed by using pointed grazing-incidence optics and a channel-electron multiplier as a photon detector. An EUV flux in the range from 55 to 150 A was detected from SS Cyg during an optical outburst at an intensity level considerably below that of Rappaport et al. (1974). Upper limits are placed on the EUV fluxes from Z Cha, VW Hyi, and AE Aqr. Multicolor optical photometry of SS Cyg and AE Aqr is also examined which was obtained simultaneously with the EUV observations. It is concluded that intrinsic EUV flux variability is probably a characteristic of SS Cyg and that the same system exhibits an extremely large range of soft X-ray luminosities while remaining at about the same visible light level. Several models for the SS Cyg system are compared with the EUV data.
Margon, B.↗
Nonperiodic optical flickering in HZ Herculis
High-speed simultaneous dual-channel photometry of HZ Her and a nearby comparison star reveal nonperiodic optical flickering in the HZ Her system on a time scale of 15 to 300 sec. The amplitude of the flickering appears to be correlated with orbital phase. Optical emission from a hot spot in a disk of material around the X-ray source cannot account for the flickering.
Moffett, T. J.↗