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The newly discovered satellite galaxy located in the Milky Way galactic anti-center region is discussed along with the possibility that a nearby gamma ray source is associated with it. The factors which led to the conclusion that the gamma ray excess is not associated with the galaxy are considered.
The response was studied of a rotating neutron star to fluctuating torques and it was found that the observed variations in the pulsation periods of the compact X-ray sources Cen X-3 and Her X-1 could be caused by short time scale fluctuations in the accretion torques acting on the neutron stars. The sizes and rates of the required fluctuations are consistent with current accretion models. Such fluctuations can cause period variations either (a) directly, by causing a random walk of the star's angular velocity or (b) indirectly, by exciting a long-period mode of the neutron star, such as the Tkachenko mode of the rotating neutron superfluid. Phenomena in compact X-ray sources and cataclysmic variables which may be caused by fluctuating mass flow rates are also discussed.
Observations with the SAS-2 high energy ( 35 MeV) gamma-ray telescope show evidence of gamma-ray emission from the radio pulsar PSR 1747-46. When the arrival times of gamma-rays from the region of the pulsar were converted to pulsar phases using the radio period and period derivative, a single peak was found in the phase plot, with a Poisson probability of occurring by chance of .00008. Independently, the time-averaged data for the PSR 1747-46 region show an enhancement over the surrounding region of the sky at the same galactic latitude, with a Poisson probability of chance occurrence of less than .008. The probability that these results are chance is the product of these two probabilities times the number of radio pulsars examined (73). This overall probability is sufficiently small (.00005) to suggest an identification of a new gamma-ray pulsar. In the gamma-ray pulsar plot, the peak falls 0.16 + or - 0.03 period after the radio pulsar peak. This phase shift is, within uncertainties, the same as that observed between the single radio peak and the first of the two gamma-ray peaks seen in the phase plot for PSR-0833-45 (the Vela pulsar).
Continuing analysis of the data from the SAS-2 high energy gamma-ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitude 310 and 45 deg, corresponding to a region within 7kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315 deg, 330 deg, 345 deg, 0 deg, and 35 deg. These peaks appear to be correlated with such galactic features and components as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic ray concentrations, and photon fields.
Gamma-ray emission was detected from the radio pulsars PSR1818-04 and PSR1747-46, in addition to the previously reported gamma-ray emission from the Crab and Vela pulsars. Since the Crab pulsar is the only one observed in the optical and X-ray bands, these gamma-ray observations suggest a uniquely gamma-ray phenomenon occurring in a fraction of the radio pulsars. Using distance estimates it is found that PSR1818-04 has a gamma-ray luminosity comparable to that of the Crab pulsar, while the luminosities of PSR1747-46 and the Vela pulsar are approximately an order of magnitude lower. This survey of SAS-2 data for pulsar correlations has also yielded upper limits to gamma-ray luminosity for 71 other radio pulsars.
Analysis of SAS-2 high energy Gamma ray data from the direction of the galactic anticenter shows that this region is characterized by: a diffuse emission from the galactic plane which has a maximum along b=0 deg and an enhancement toward negative latitudes associated with Gould's Belt, a strong point source in the direction of the Crab nebula, and a second intense localized source near galactic coordinates 195 deg, +5 deg. Gamma ray emission from the Crab source is dominated by a pulsed flux from PSR 0531+21. The total flux above 100MeV is 3.7 + or - 0.8 million/sq cm s. The source near 195 deg, + 5 deg has a flux above 100 MeV of 4.3 + or - 0.9 million/sq cm s. Its spectrum appears flatter than that of the Crab. The diffuse galactic plane emission at negative lattitudes shows a general correlation with the local matter distribution associated with Gould's Belt. The calculated Gamma ray intensity agrees well with the SAS-2 observations.
Energetic (E35 MeV) Gamma rays were observed from Cyg X-3 with the SAS-2 Gamma ray telescope. They are modulated at the 4.8 sup h period observed in the X-ray and infrared regions, and within the statistical error are in phase with this emission. The flux above 100 MeV has an average value of (4.4 + or - 1.1)x 10 to the -6 power/sq cm/sec. If the distance to Cyg X-3 is 10 kpcs, this flux implies a luminosity of more than 10 to the 37th power ergs/s if the radiation is isotropic and about 10 to the 36th power ergs/s if the radiation is restricted to a cone of one steradian, as it might be in a pulsar.
It is suggested that the observed soft X-rays from Her X-1 are the result of an opaque gas shell which surrounds the neutron star at a radius where centrifugal force and the magnetic field impede the gravitational infall of the gas and which absorbs a substantial fraction of the hard X-ray flux, reradiating it as soft X-rays. Two highly idealized models for the shell are constructed in which the radius and temperature are 7000 km and 550,000 K or 1300 km and 1.5 million K, respectively. These models are intended to show that a gas shell with interesting spectral characteristics is likely to occur at a radius of 2000 to 7000 km from the neutron star if the magnetic field impedes the gas infall at this radius and that such a shell is indicated by the soft X-ray observations. A possible geometry is considered wherein the shell is a wide opaque ring at the magnetic equator, becomes transparent at high latitudes, and becomes opaque again at the magnetic poles.
An experimental investigation was conducted in the Langley Unitary Plan wind tunnel to estimate the peak aerodynamic heating on the space shuttle solid rocket booster during the descent phase of its flight. Heat transfer measurements were obtained using 0.013 scale models instrumented with thermocouples at a Mach number of 3.70, Reynolds number per meter of 11.48 million, and angles of attack from 0 to 180 deg. At angles of attack of 0 and 180 deg, heat transfer measurements on the cylindrical section of the model between the conical nose and ring interaction region were in good agreement with flat plate strip theory for laminar and turbulent flow. At angles of attack up to 30 deg, measurements on this section of the model were in good agreement with laminar swept-cylinder theory, whereas at angles of attack from 120 to 180 deg, the measurements were in good agreement with turbulent swept-cylinder theory. The good agreement with turbulent theory indicated that large flow disturbances created by the nozzle and afterbody flare at these large angles of attack influenced the downstream heating primarily by promoting boundary layer transition. Measurements obtained at 90 deg angle of attack were indicative of laminar flow.
Average temperature time history calculations of the test media and tunnel walls for cryogenic wind tunnels have been developed. Results are in general agreement with limited preliminary experimental measurements obtained in a 13.5-inch pilot cryogenic wind tunnel.
Continuing analysis of the data from the SAS-2 high energy gamma ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitudes 310 deg and 45 deg, corresponding to a region within 7 kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315, 330, 345, 0, and 35 deg. These peaks appear to be correlated with galactic features and components such as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic-ray concentrations, and photon fields.
Gamma ray emission was detected from the radio pulsars PSR 1818-04 and PSR 1747-46, in addition to the previously reported gamma ray emission from the Crab and Vela pulsars. Because the Crab pulsar is the only one observed in the optical and X-ray bands, these gamma ray observations suggest a uniquely gamma ray phenomenon occurring in a fraction of the radio pulsars. PSR 1818-04 has a gamma ray luminosity comparable to that of the Crab pulsar, whereas the luminosities of PSR 1747-46 and the Vela pulsar are approximately an order of magnitude lower. SAS-2 data for pulsar correlations yielded upper limits to gamma ray luminosity for 71 other radio pulsars. For five of the closest pulsars, upper limits for gamma ray luminosity are found to be at least three orders of magnitude lower than that of the Crab pulsar. Gamma ray enhancement near the Milky Way satellite galaxy and the galactic plane in the Cygnus region is also discussed.
A recent study by Mruk et al. (1975) of convective heat transfer on the leeward surface of a space shuttle orbiter fuselage configuration has yielded experimental data on a fuselage-wing geometry and a bare fuselage (without wings). The present paper summarizes that portion of the investigation related to the bare fuselage tests in which data were obtained for an angle of attack of 90 deg so as to produce nominal planar flow. In addition, some supplementary data were obtained at an angle of attack of 30 deg. The bare fuselage geometry, when immersed in a nearly normal approaching flow, behaves as a cylinder of noncircular cross section and moderate aspect ratio. The data presented were obtained with air as the test gas in a 96-in. hypersonic shock tunnel over a specified range of test conditions. The test program included three values of windward surface temperature and two values of leeward section temperature. Leeward convection is characterized by two values of Stanton number; one for the attached flow just prior to separation and the other for the recirculating zone.
Evidence is reported for the observation of gamma-ray emission from the radio pulsar PSR 1747-46 by the gamma-ray telescope aboard SAS 2. The evidence is based on the presence of both an approximately 3-sigma enhancement of gamma rays at the pulsar's location and an approximately 4-sigma peak in the phase plot of 79 gamma-ray events whose phase was calculated from the pulsar's known period. The gamma-ray pulsation is found to appear at a phase lag of about 0.16 from that predicted by the radio observations. The pulsed gamma-ray fluxes above 35 MeV and 100 MeV are estimated, and it is shown that the gamma-ray pulse width is similar to the radio pulse width. It is concluded that PSR 1747-46 is a most likely candidate for pulsed gamma-ray emission.
Energetic (exceeding 35 MeV) gamma-rays have been observed from the direction of Cygnus X-3 with the SAS-2 gamma-ray telescope. The statistical significance of the excess above the galactic and diffuse radiation is approximately 4.5 sigma. In addition, the gamma-ray flux is modulated at the 4.8-hr period observed in the X-ray and infrared regions, and within the statistical error is in phase with this emission. The flux above 100 MeV has an average value of about 4.4 millionths photon/sq cm per sec. If the distance to Cygnus X-3 is 10 kpc, this flux implies a luminosity of more than 10 to the 37th power erg/s if the radiation is isotropic and about 10 to the 36th power erg/s if the radiation is restricted to a cone of 1 steradian, as it might be in a pulsar. Upper limits are presented for the gamma-ray flux from other known or suspected periodic X-ray sources.
Final results are presented for SAS-2 observations of high-energy gamma-rays from the galactic anticenter region. Three main gamma-ray features are shown to characterize this region: a localized source associated with the Crab Nebula and its pulsar, another localized source near galactic coordinates 195 deg, +5 deg, and a general enhancement of the diffuse background 10 to 15 deg south of the galactic plane, which is associated with the Gould Belt. For the Crab, it is found that the radiation is mostly pulsed, the pulsed fraction increases with energy, and the intensity of the radiation in the main and interpulse peaks is approximately the same. The other localized source, provisionally designated as gamma 195+5, is found to have a harder spectrum than the Crab but no obvious radio counterpart; emission from an external galaxy is ruled out.
The aerodynamic, stability, and control characteristics of several supersonic fighter airplane concepts are examined. The configurations, which are based on Soviet design concepts, include fixed-wing aircraft having delta wings, swept wings, and trapezoidal wings, and a variable wing-sweep aircraft. Each concept employs aft tail controls. The concepts vary from lightweight, single-engine, air superiority, point interceptor, or ground attack types to larger twin-engine interceptor and reconnaissance designs. Analytical and experimental results indicate that careful application of the transonic or supersonic area rule can provide nearly optimum shaping for minimum drag for a specified Mach number requirement. In addition, through the proper location of components and the exploitation of interference flow fields, the concepts provide linear pitching moment characteristics, high control effectiveness, and reasonably small variations in aerodynamic center location with a resulting high potential for maneuvering capability.
The SAS-2 identified six localized high energy (greater than 35 MeV) gamma ray sources. Four of these are the radio pulsars, PSR 0531+21, PSR 0833-45, PSR 1818-04, and PSR 1717-46 discovered in a search of 75 radio pulsars. The fact that only one of these is observed in X-rays, and the significant differences in pulse profiles in the gamma ray and radio observations, leads to the speculation that different mechanisms are involved.