DEMO: autonomous science analysis, planning, and execution on the EO-1 mission
Explore the source record for details and available documents.
EO-1 autonomous science ASE onboard decision-makin↗
Engineering topics
Shulman, S.
Publications and source records attributed to Shulman, S..
Autonomous Science on the EO-1 Mission
In mid-2003, we will fly software to detect science events that will drive autonomous scene selectionon board the New Millennium Earth Observing 1 (EO-1) spacecraft. This software will demonstrate the potential for future space missions to use onboard decision-making to detect science events and respond autonomously to capture short-lived science events and to downlink only the highest value science data.
autonomous systems robust execution↗
3 keV to 2 MeV observations of four gamma-ray bursts
Simultaneous X and gamma ray spectra were obtained for four gamma ray burst events using satellite instrumentation. The P78-1 satellite proportional counters recorded X-ray data in the 3-10 keV range, while Pioneer Venus Orbiter and ISEE 3 sensors had a 3 keV lower limit for events. The positively correlated data covered the events GB 790307, 790325, 790504, and 790731. The time histories of the X and gamma ray energies did not correlate well. The post-gamma ray phase of GB 790307 displayed features of simple cooling, and in conjunction with soft X-ray data suggested an origin in an optically thin fireball. However, the data were equally well-fitted by a model of an emitting hot spot on a neutron star. The data negated any concept that gamma ray bursts evolve similarly to classical X-ray bursts.
Laros, J. G.↗
Observations of outbursts from the recurrent X-ray transient A0538-66 and LMC X-4
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.
Skinner, G. K.↗
Soft X-ray sources in the bar of the Large Magellanic Cloud
X-ray observations of the Large Magellanic Cloud were made with two collimated proportional counters having high angular resolution, a wide spectral dynamic range and a large aperture. Counting rates in the two detectors during the entire rocket flight are presented, and a number of soft X-ray (0.5-2 keV) sources were found in the bar of the LMC, having luminosities between 10 to the 37th and 10 to the 38th ergs/s. Emission in the 0.15-0.28 keV band from LMC X-3 was also detected.
Mckee, J. D.↗
Rapid X-ray variability of PKS 2155-304
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.
Snyder, W. A.↗
The X-ray light curve of 4U 2129+47
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.
Ulmer, M. P.↗
An X-ray survey of distant rich clusters of galaxies with HEAO 1
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.
Ulmer, M. P.↗
X-ray emission from gamma-ray sources in the galactic anticentre region
An X-ray survey of three high energy gamma-ray sources in the galactic anticenter region conducted using the large area sky survey instrument on HEAO 1 is presented. The sensitivity of this survey is highest reported, and two, and possibly three, X-ray sources were detected in the vicinity of gamma 195+5. Three new X-ray sources have been discovered within a few degrees of CG176-7, but none overlaps the gamma-ray error box. These results demonstrate that gamma-ray sources like CG195+4 and CG176-7 have emission characteristics different from the Crab pulsar, but may be similar to the Vela pulsar. Alternatively, the lack of detectable X-ray flux suggests that the gamma-ray emission arises from cosmic-ray interactions in dense interstellar clouds. An interesting feature of the new X-ray sources is that four of them may be associated with early-type stars which exhibit emission lines.
Share, G. H.↗
Observations of the structure of the diffuse X-ray emission from the Coma cluster
The Coma cluster has been scanned by an array of large X-ray proportional counters equipped with 10 min x 4 deg (FWHM) collimators. The results suggest the peak surface brightness is not coincident with one of the two giant elliptical galaxies, NGC 4889 and 4874, and show the X-ray emission to be more extended in the 0.5-1.5-keV band than in the 1.5-5-keV band. No evidence is found for concentrated X-ray sources, like those in M87 and NGC 1275. The X-ray surface brightness contours have an ellipticity which resembles that of the galaxy mass distribution, and evidence is found for clumpiness in the intracluster gas.
Johnson, M. W.↗
GX339-4 - A new black hole candidate
HEAO-1 observations of aperiodic variability in the galactic X-ray source GX339-4 (4U 1658-48) on time scales of tens of milliseconds to a few seconds are reported. It is shown that the overall characteristics of GX339-4 place it in the same class of X-ray sources as Cyg X-1 and Cir X-1, which are candidates for black holes in binary systems. The detection of X-ray flares from GX339-4 is discussed, particularly a series of five sequential flares with separations of about 250 ms.
Samimi, J.↗
Faint extragalactic objects and the unidentified high latitude X-ray sources
Classes of extragalactic objects that have been identified with faint high-galactic-latitude X-ray sources in the Fourth Uhuru and Ariel 5 Catalogs are examined. Sources with declinations of at least -30 deg, galactic latitudes of at least 20 deg (absolute value), and error boxes of 1.0 sq deg are considered. It is shown that clusters of galaxies constitute the most numerous class of extragalactic sources and that Seyfert galaxies are the next largest class. Unidentified high-latitude X-ray sources are discussed. Preliminary results obtained with the A-1 instrument aboard HEAO 1 are reported which indicate that a substantial fraction of unidentified sources are highly variable and may be identified with active galaxies.
Shulman, S.↗
High-resolution observations of X-ray sources at the galactic center
A region about 1 deg of arc in radius and centered on the galactic nucleus has been surveyed during a rocket flight, using X-ray detectors equipped with 10-arcmin by 4-deg (FWHM) collimators. The extended source 4U 1743-29 has been resolved into at least four discrete sources having luminosities (2-10 KeV) between 4 by 10 to the 36th power and 3.5 by 10 to the 37th power erg/s.
Cruddace, R. G.↗
Soft X-ray emission from a newly discovered supernova remnant in Cygnus
Explore the source record for details and available documents.
Snyder, W. A.↗
Soft X-ray sources and supernova remnants in Cygnus - Rocket and Apollo-Soyuz results
Soft X-ray observations of the Cygnus region obtained from proportional counters aboard a rocket and also on the Apollo-Soyuz mission are reported. It is found that Cyg X-6, a source whose flux in confined to the 0.5-2.0-keV band, is a long narrow filament oriented nearly perpendicular to the galactic plane. This feature has a linear dimension greater than or of the order of 150 parsecs, and its spectrum is adequately described by an exponential. Another intense soft source whose flux is also confined to the 0.5-2.0-keV band has been discovered near Gamma Cygni. This source, designed Cyg X-7, has a spectrum characterized by a temperature of 1.5 to 5 million K and a hydrogen column density of at least 10 to the 21st power per sq cm. The possible association of Cyg X-7 with the supernova remnant DR 4 is discussed. An interpretation of this object in terms of the standard adiabatic spherical-shock-wave model yields plausible values for the free paramenters. HB 21, another old supernova remnant, has not been detected as a soft X-ray source.
Davidsen, A. F.↗
X-ray emission from the supernova remnant MSH 14-63
X-ray emission in the 0.6-2.5-keV energy range has been detected from the supernova remnant MSH 14-63. The observed flux is 3.5 by 10 to the -10th power erg/sq cm per sec. The absence of lower-energy X-rays indicates a hydrogen column density consistent with the radio and optical distance estimates of 2.5 kpc.
Naranan, S.↗
A new measurement of the spin-up rate of SMC X-1
Observations of the X-ray pulsar, SMC X-1, made from an Aerobee rocket and an Apollo spacecraft have been re-analyzed. The rotation periods found have been combined with observations made from Uhuru, SAS-3, and Ariel 5 to obtain a new measurement of the spin-up rate of SMC X-1.
Yentis, D.↗
X-ray evidence for the supernova origin of the North Polar spur
Soft X-ray observations during four scans across the North Polar radio continuum spur have provided additional evidence that the spur encircles an old supernova remnant. From the measured intensity of the X-ray emission, and the known diameter of the remnant, it is estimated that its age is several hundred thousand years and that the supernova was of Type II, with an energy between 10 to the 51st and 10 to the 53rd ergs.
Cruddace, R. G.↗