view Abstract Citations (50) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Millisecond variability of Cygnus X-1. Meekins, J. F. ; Wood, K. S. ; Hedler, R. L. ; Byram, E. T. ; Yentis, D. J. ; Chubb, T. A. ; Friedman, H. Abstract The May 7, 1978 HEAO 1 spacecraft observations of Cygnus X-1 with a 10 microsec time resolution have revealed 3 ms variability, as well as a 300 ms component and features which extend to 6 s. Emission on time scales shorter than 1 s can be approximately modeled as a superposition of uncorrelated 3 ms and 300 ms shot contributions, both with peak luminosities near 10 to the 37th ergs/s, and with shot rates of about 10/s and 0.2/s, respectively. The 3 ms variability is consistent with the time scales expected for variability near the inner edge of a viscous accretion disk that surrounds a 10-solar mass black hole. Publication: The Astrophysical Journal Pub Date: March 1984 DOI: 10.1086/161793 Bibcode: 1984ApJ...278..288M Keywords: Accretion Disks; Binary Stars; Black Holes (Astronomy); Cygnus Constellation; Variable Stars; X Ray Sources; Bursts; Heao 1; Shot Noise; Statistical Analysis; Time Measurement; Astrophysics full text sources ADS | data products SIMBAD (4)

view Abstract Citations (396) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The HEAO A-1 X-ray source catalog. Wood, K. S. ; Meekins, J. F. ; Yentis, D. J. ; Smathers, H. W. ; McNutt, D. P. ; Bleach, R. D. ; Byram, E. T. ; Chupp, T. A. ; Friedman, H. ; Meidav, M. Abstract The catalog of X-ray sources detected during the NRL Large Area Sky Survey (LASS) with the HEAO 1 satellite is presented. The catalog is derived from the first six months of data from HEAO 1 and includes sources detected during one full scan. Positions and intensities for a total of 842 different sources are included, with a limiting flux of 250 nJy at 5 keV. The catalog is more than 90 percent complete at a flux level equivalent to 1.5 microjoules at 5 keV for a Crab-like spectrum. Cross-references with published literature are provided and coincidental identifications are proposed for some of the sources which have been never studied before. A cross-sectional line drawing of the sensor module of HEAO I is also provided. Publication: The Astrophysical Journal Supplement Series Pub Date: December 1984 DOI: 10.1086/190992 Bibcode: 1984ApJS...56..507W Keywords: Astronomical Catalogs; Heao 1; Spaceborne Astronomy; X Ray Sources; Cataclysmic Variables; Galactic Clusters; Pulsars; Quasars; Seyfert Galaxies; Sky Surveys (Astronomy); Supernova Remnants; Tables (Data); Astronomy full text sources ADS | data products SIMBAD (900) NED (102) CDS (2) Related Materials (1) Catalog: 1995yCat.7080....0W

view Abstract Citations (8) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H 0547-14 : X-ray flux from a weak gamma-ray burst. Ambruster, C. ; Wood, K. S. ; Meekins, J. F. ; Yentis, D. J. ; Smathers, H. W. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract Data concerning a fast X ray transient observed by the HEAO 1 on March 17, 1978 are discussed. The object, labeled H0547-14, was located in Lepus, with galactic coordinates 219.37 deg longitude, b = -20.12 deg in the anticenter direction. A 10 sec scan of the transient was obtained with proportional counter detectors. An X ray luminosity of more than 5.1 x 10 to the 31st ergs/sec was measured as a lower limit, with the decay taking 17 min. A lower limit to the flare was set at 30 sec. The flux intensity resided in the range 4.4/1 billion-4/100 million erg/sq cm per sec, with a rise time of a factor of 10 in about 5 sec. Possible characterizations of the object, as either a gamma ray burst or as an M dwarf star, are discussed. Publication: The Astrophysical Journal Pub Date: June 1983 DOI: 10.1086/161086 Bibcode: 1983ApJ...269..779A Keywords: Gamma Ray Bursts; M Stars; Stellar Flares; X Ray Sources; Bremsstrahlung; Dwarf Stars; Flare Stars; Heao 1; Late Stars; Light Curve; Astrophysics full text sources ADS | data products SIMBAD (1)

view Abstract Citations (13) References (49) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An 80 day X-ray light curve of 3C 371 Snyder, W. A. ; Wood, K. S. ; Yentis, D. J. ; Meekins, J. F. ; Smathers, H. W. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract The Large Area Sky Survey (LASS) experiment on HEAO 1 that monitored the N galaxy/BL Lacertae object 3C 371 from August 19 to November 7, 1977 is discussed, noting that statistically significant threefold or larger intensity variations were observed in the flux range 0.5-20 keV. It is found that the degree of variability depends on the time of observation, with the source sometimes appearing constant and sometimes changing on time scales of 1 to 2 weeks. Also observed was an X-ray flare that lasted approximately 25 days. The total 80-day X-ray light curve is seen as suggesting either a superposition of X-ray flares or a variable injection rate that changes on weekly time scales. The observed X-ray flux is found to be consistent with that expected by extrapolating the nonthermal optical spectrum, suggesting that the optical to X-ray flux could be synchrotron radiation, provided that it is possible to account for the patterns of variability seen at optical and X-ray wavelengths and to dispose of inverse Compton difficulties. Publication: The Astrophysical Journal Pub Date: August 1982 DOI: 10.1086/160144 Bibcode: 1982ApJ...259...38S Keywords: Bl Lacertae Objects; Heao 1; Light Curve; Synchrotron Radiation; X Ray Sources; Astronomical Models; Galactic Nuclei; Radio Astronomy; Relativistic Particles; Sky Surveys (Astronomy); Astrophysics full text sources ADS | data products NED (1)

view Abstract Citations (27) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for coherent emission with a 12 millisecond period during a burst from MXB 1728-34. Sadeh, D. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. ; Hedler, R. L. ; Meekins, J. F. ; Wood, K. S. ; Yentis, D. J. Abstract Four bursts of MXB 1728-34 have been observed with the HEAO A-1 instrument using 5-ms timing resolution. The rapid initial rise has been resolved in all four bursts. Fourier analysis indicates the presence of a periodic component with a 12.2-ms period during one of the bursts. Epoch-folding analysis confirms this period and further indicates that the period decreases with time, with dP/dt = -10 to the -6th. The signal has a probability of 2.5 x 10 to the -9th to occur at random, and an expectation of 0.003 to occur in the number of epoch foldings performed. Attempts to explain the 12-ms period as a neutron star spin period meet with severe difficulties. The observed periodic emission is most likely associated with the Kepler orbital period in a viscous accretion disk surrounding a black hole of about 10 solar masses. Publication: The Astrophysical Journal Pub Date: June 1982 DOI: 10.1086/159980 Bibcode: 1982ApJ...257..214S Keywords: Bursts; Coherent Radiation; Emission Spectra; Kepler Laws; Stellar Mass Accretion; X Ray Spectra; Black Holes (Astronomy); Fourier Analysis; Heao 1; Neutron Stars; Periodic Variations; Random Signals; Temporal Resolution; X Ray Astronomy; Astrophysics full text sources ADS | data products SIMBAD (4)

view Abstract Citations (25) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A 4.2 second period in the gamma-ray burst of 1977 October 29 Wood, K. S. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. ; Meekins, J. F. ; Share, G. H. ; Yentis, D. J. Abstract A burst profile of high statistical precision is presented for the gamma-ray burst of October 29, 1977, detected by the HEAO 1 Large Area Sky Survey Experiment. Data from all modules active at the time are summed together in the profile. Several local maxima, separated by intervals of about 4s, are plainly visible, and local minima fall approximately halfway between adjacent maxima. Two methods are used to analyze the profile: (1) by fitting a function that includes a damped sinusoid directly to the total profile, and (2) by fitting again without any periodic component, subtracting this fit from the data, and examining the power spectrum of the residuals. The limitations of fitting periods to bursts of short duration are described, and implications of period detections for neutron star models of gamma bursts are developed. It is shown that gamma bursters could be neutron stars in binary systems. Publication: The Astrophysical Journal Pub Date: July 1981 DOI: 10.1086/159074 Bibcode: 1981ApJ...247..632W Keywords: Binary Stars; Flare Stars; Gamma Ray Astronomy; Heao 1; Neutron Stars; Fast Fourier Transformations; Light Curve; Sky Surveys (Astronomy); Stellar Evolution; Stellar Luminosity; Stellar Models; Astronomy full text sources ADS |

view Abstract Citations (33) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A survey of rich clusters of galaxies with HEAO 1. II. Ulmer, M. P. ; Kowalski, M. P. ; Cruddace, R. G. ; Johnson, M. ; Meekins, J. ; Smathers, H. ; Yentis, D. ; Wood, K. ; McNutt, D. ; Chubb, T. ; Byram, E. T. ; Friedman, H. Abstract Results are presented of an X-ray survey of approximately 1900 Abell clusters of galaxies performed with the NRL large-area X-ray detectors on HEAO 1. The cluster luminosity function derived from the observations made at ecliptic longitudes between 80 and 180 deg and 260 and 360 deg is fit with both power law and exponential relations, and used to estimate a total contribution of Abell clusters to the volume emissivity of the diffuse X-ray background of between 3 and 10%. No strong correlation is found between X-ray luminosity and Bautz-Morgan class, richness class or 26-MHz radio power, although B-M type I and Abell richness class 3 appear more likely to be strong X-ray sources. A correlation is suggested between optical radius and X-ray luminosity. Publication: The Astrophysical Journal Pub Date: February 1981 DOI: 10.1086/158636 Bibcode: 1981ApJ...243..681U Keywords: Galactic Clusters; Heao 1; X Ray Sources; Astronomical Models; Correlation; Luminosity; Astrophysics full text sources ADS | data products NED (42) SIMBAD (37)

view Abstract Citations (69) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of outbursts from the recurrent X-ray., transient A 0538-66 and LMC X-4. Skinner, G. K. ; Shulman, S. ; Share, G. ; Evans, W. D. ; McNutt, D. ; Meekins, J. ; Smathers, H. ; Wood, K. ; Yentis, D. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract Nine X-ray outbursts from the LMC have been observed with the HEAO 1 Large-Area Sky Survey Instrument. Some are shown to originate in the recurrent transient A0538-66, confirming the proposed 16 day periodicity and showing that the duration of the events can be as long as 14 days or as short as a few hours. Deviations from precise periodicity can be attributed to phase jitter or to a change in period occurring around the time of an exceptionally long outburst. Other outbursts which are irregular and consistently shorter originate in LMC X-4. A long-term light curve indicates that the LMC X-4 outbursts occur only when the source is in a high state, but are not strongly correlated with the binary phase. Publication: The Astrophysical Journal Pub Date: September 1980 DOI: 10.1086/158267 Bibcode: 1980ApJ...240..619S Keywords: Magellanic Clouds; Spaceborne Astronomy; X Ray Sources; Heao 1; Light Curve; Periodic Variations; Sky Surveys (Astronomy); Astrophysics full text sources ADS | data products SIMBAD (8)

view Abstract Citations (50) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rapid X-ray variability of PKS 2155-304. Snyder, W. A. ; Davidsen, A. F. ; Wood, K. ; Kinzer, R. ; Smathers, H. ; Shulman, S. ; Meekins, J. F. ; Yentis, D. J. ; Evans, W. D. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. ; Margon, B. Abstract The X-ray emitting BL Lacertae object PKS 2155-304 was observed with NRL's Large Area Sky Survey Experiment on HEAO 1 during November 10-16, 1977. Variations of a factor of 2 in the 0.5-20 keV intensity are found on time scales as short as 6 hours. Variations on time scales of 1 s, as reported by the HEAO A-2 LED experiment, are not confirmed in near-simultaneous observations. Optical spectroscopy is also presented which does not confirm the presence of previously reported redshifted (Z = 0.17) forbidden O III line emission. The question of the redshift of this object is still open. Publication: The Astrophysical Journal Pub Date: April 1980 DOI: 10.1086/183223 Bibcode: 1980ApJ...237L..11S Keywords: Bl Lacertae Objects; Pulsed Radiation; Spaceborne Astronomy; X Ray Sources; Astronomical Spectroscopy; Calcium; Heao 1; Iron; Light Curve; Line Spectra; Sky Surveys (Astronomy); Variability; X Ray Spectra; Astronomy full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (20) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An X-ray survey of distant rich clusters of galaxies with HEAO 1. Ulmer, M. P. ; Shulman, S. ; Evans, W. D. ; Johnson, W. N. ; McNutt, D. ; Meekins, J. ; Share, G. H. ; Yentis, D. ; Wood, K. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract The paper presents a 1-10-keV survey of distance class 4, 5, and 6 Abell clusters using the HEAO 1 NRL large area survey experiment. The survey is a little less than 1/30 of the Abell catalog. Eleven clusters are identified with X-ray sources, and X-ray upper limits are provided for 60 others. Publication: The Astrophysical Journal Pub Date: January 1980 DOI: 10.1086/157638 Bibcode: 1980ApJ...235..351U Keywords: Astronomical Catalogs; Galactic Clusters; Heao 1; X Ray Astronomy; Error Analysis; Size (Dimensions); Spaceborne Experiments; Uhuru Satellite; Astrophysics full text sources ADS | data products SIMBAD (61) NED (60)

view Abstract Citations (15) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The X-ray light curve of 4U 2129+47. Ulmer, M. P. ; Shulman, S. ; Yentis, D. ; Evans, W. D. ; McNutt, D. ; Meekins, J. ; Wood, K. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract The light curve of 4U 2129+47 is presented showing that it almost certainly has a period of approximately 0.22 days. This is the same period as the optical candidate proposed by Thorstensen et al. (1979). Binary X-ray source models, consisting of an M dwarf plus either a neutron star or a white dwarf, are briefly discussed. Publication: The Astrophysical Journal Pub Date: February 1980 DOI: 10.1086/183181 Bibcode: 1980ApJ...235L.159U Keywords: Binary Stars; Light Curve; Stellar Models; X Ray Sources; Dwarf Stars; M Stars; Neutron Stars; Astronomy full text sources ADS | data products SIMBAD (1)

view Abstract Citations (23) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A search for extended halos of hot gas in the Perseus, Virgo, and Coma Clusters Ulmer, M. P. ; Cruddace, R. G. ; Wood, K. ; Meekins, J. ; Yentis, D. ; Evans, W. D. ; Smathers, H. W. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract Observations of the Perseus cluster by the HEAO 1 satellite have revealed a faint X-ray halo extending at least 2.5 deg from the center and contributing between 5% and 20% to the total luminosity. This may be of nonthermal origin, but it also may be explained in terms of hot gas bound by the gravitational field of the cluster. Statistical uncertainties made it impossible to detect any such halo in the Coma cluster. Observations of the Virgo cluster confirmed the detection by the Ariel 5 satellite of a broad region of faint X-ray emission (core radius 60 arcmin). If the very extended X-ray emission from Virgo is due to hot intracluster gas, the density of this gas is lower than expected from a consideration of gas and galaxy densities in the Perseus cluster. Publication: The Astrophysical Journal Pub Date: February 1980 DOI: 10.1086/157717 Bibcode: 1980ApJ...236...58U Keywords: Cosmic Gases; Galactic Clusters; High Temperature Gases; Intergalactic Media; X Ray Sources; Gas Density; Halos; Heao 1; Spaceborne Astronomy; Astrophysics full text sources ADS | data products NED (3)

view Abstract Citations (19) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The continuous spectrum of Markarian 421 during periods of X-ray satellite observations. Mufson, S. L. ; Wisniewski, W. Z. ; Wood, K. ; McNutt, D. P. ; Yentis, D. J. ; Meekins, J. F. ; Byram, E. T. ; Chubb, T. A. ; Friedman, H. Abstract New UBVRI photometry of Mrk 421 obtained during periods of X-ray satellite observations are presented. An X-ray light curve for 1977 November from the HEAO A-1 experiment is also given. The decomposition of the UBVR fluxes into a compact nonthermal component and an extended galactic component shows that there are coordinated variations in the optical nonthermal and X-ray emission. The data are consistent with the hypothesis that the mini-BL Lac object is emitting by the synchrontron-self-Compton process. The host galaxy of this composite source has properties like those of a giant elliptical. Publication: The Astrophysical Journal Pub Date: October 1980 DOI: 10.1086/158319 Bibcode: 1980ApJ...241...74M Keywords: Astronomical Photometry; Bl Lacertae Objects; Continuous Spectra; Galactic Radiation; Spaceborne Astronomy; Ubv Spectra; Elliptical Galaxies; Light Curve; Satellite Observation; X Ray Astronomy; Astrophysics; BL Lacertae Objects:Elliptical Galaxies; Elliptical Galaxies:Photometry; Elliptical Galaxies:X-Ray Sources full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (25) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Identification of a faint X-ray source with the W UMa star VW Cep. Carroll, R. W. ; Cruddace, R. G. ; Friedman, H. ; Byram, E. T. ; Wood, K. ; Meekins, J. ; Yentis, D. ; Share, G. H. ; Chubb, T. A. Abstract The NRL instrument aboard the HEAO 1 satellite has detected a faint X-ray source, which has been identified tentatively with the contact binary star (W UMa variable) VW Cephei. Its luminosity is between 3 x 10 to the 30th and 4 x 10 to the 31st ergs/sec (0.1-10 keV), and the results suggest some variation of the X-ray flux with phase. Publication: The Astrophysical Journal Pub Date: January 1980 DOI: 10.1086/183162 Bibcode: 1980ApJ...235L..77C Keywords: Binary Stars; Stellar Spectrophotometry; X Ray Astronomy; X Ray Stars; Angular Distribution; Heao 1; Light Curve; Stellar Luminosity; Astronomy full text sources ADS | data products SIMBAD (1)

CIRCINUS X–1 (4U1516–56) was first detected in 1969 (ref. 1) and has since been studied in X-ray, radio, and optical wavelengths. Particular interest in this source has resulted from its resemblance to Cygnus X–1—a suspected black hole. Both objects have X-ray luminosities in the range 1037–1038 erg s−1 (refs 2,3). Both exhibit rapid intensity variations with timescales as low as 1 ms (refs 4,5), and as long as seconds or days6–8. Both X-ray sources are in binary systems; the orbital period reported for Cir X–1 is 16.585 d (ref. 9). Cir X–1 differs from Cyg X–1 in that the total mass of the binary pair is unknown. While an optical candidate has been found10, no estimation of its mass has been made, so that the evidence for its being a black hole is not as strong for Cir X–1. Variable IR emission11 has been reported from the companion. There have been conflicting reports of X-ray periods of the order of seconds: Margon et al.1 suspected a period of 0.685 s and Toor reported a possible 2.2 s period4. We report here our investigations, using HEAO A-1, of these semi-periodic pulsations in Cir X–1.