Deep Space Network availability for radio and radar astronomy
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DSN radio radar↗
Engineering topics
Geldzahler, B. J.
Publications and source records attributed to Geldzahler, B. J..
Search for gamma-ray emission lines from SS 433: 2: 1980-1989
We have searched through the Solar Maximum Mission satellite gamma-ray spectrometer database for evidence of red and blue Doppler-shifted 1.37 MeV (24)Mg* nuclear lines. The data were obtained between 1980 and 1989 and span a total of 720 days when SS 433 was in the field of view. No evidence of Doppler-shifted line emission was found in any of our spectra. The range of 3 sigma upper limits for individual 9 day integration periods was (0.8-2.4) x 10(exp -3) photons/sq cm/s for the blue beam, encompassing the approximately 1.5 MeV feature reported by Lamb et al., and (0.2-2.1) x 10(exp -3) photons/sq cm/s for the red beam, encompassing the reported approximately 1.2 MeV feature. The average 3 sigma upper limit in each beam for shifted 1.37 MeV was 1.5 x 10(exp -3) photons/sq cm/s for single 9 day integration. The 3 sigma upper limits over 56 9 day integration intervals (504 days) for the red beam and 69 intervals (621 days) for the blue beam are 1.2 x 10(exp -4) photons/sq cm/s. The new limits can be reconciled with the HEAO 3 results only if SS 433 emits gamma rays at or above the SMM sensitivity limit on rare occasions due to variable physical conditions in the system.
Geldzahler, B. J.↗
The radio 'lobes' of Scorpius X-1 are unrelated background sources
The VLA between 1981 and 1990 are used to produce high-resolution images of the radio emission from the region near Sco X-1. The radio proper motion of Sco X-1 was measured at 0.0148 +/-0.0011/yr, which agrees with the optical determination for the X-ray-emitting binary system. The proper motions of two nearby radio sources, juxtaposed 1 arcmin to the NE and to the SW, were measured and found to be stationary in the sky with upper limits of 0.004 arcsec/yr. A deep radio image of the 10-arcsec extended SW source shows a morphology strikingly similar to that of a typical luminous extragalactic radio source, which contains two edge-brightened lobes, a jet, and a core. The possibilities that the NE source, although nearly stationary in the sky, is associated with Sco X-1, are discussed, and it is concluded that it is an unrelated background source. It is inferred that Sco X-1 is not a miniature triple source or a 'microquasar', and its radio emission is confined to the binary system.
Fomalont, E. B.↗
Search for Doppler-shifted gamma-ray emission from SS 433 using the SMM spectrometer
Data accumulated from 1980 to 1983 with the Gamma Ray Spectrometer aboard NASA's Solar Maximum Mission (SMM) satellite were searched for evidence of red and blue Doppler-shifted 1.37 MeV Mg-24 nuclear lines from SS 433. The SMM data base covers 270 days when SS 433 was in the field of view and includes periods of radio flaring and quiescence. No evidence was found for Doppler-shifted line emission in any of the spectra. The range of 3-sigma upper limits for individual 9 day integration periods was 0.0008-0.0023 photons/sq cm per sec for the blue beam, encompassing the reported about 1.5 MeV line, and 0.0008-0.002 photons/sq cm per sec for the red beam, encompassing the reported about 1.2 MeV line; the average 3-sigma upper limit in each beam for shifted about 1.37 MeV lines is 0.0015 photons/sq cm per sec for single 9 day integrations. The 3-sigma upper limit on 1.37 MeV gamma-ray emission over 23 9-day integration intervals for the red beam and 28 intervals for the blue beam is 0.0002 photons/sq cm per sec. These new limits from SMM can be reconciled with the HEAO 3 results only if SS 433 emits gamma radiation at or above the SMM sensitivity limit on rare occasions due to variable physical conditions in the system.
Geldzahler, B. J.↗
Search for gamma ray lines from SS433
Data obtained with the Gamma Ray Spectrometer (0.3 to 9 MeV) aboard the Solar Maximum Mission satellite from 1980 to 1985 for evidence of the reported Doppler shifted lines from SS433 were examined. The data base covers a total of 468 days when SS433 was in the field of view and includes times of quiescent and flaring radio activity. In 9 day integrations of the SMM data no evidence is found for gamma ray line emission from SS433. The 99% confidence upper limits for 9 day integrations of the shifted 1.37 and 6.1 MeV lines are 0.0013 gamma/sq cm-s and 0.0007 gamma/sq cm-s, respectively. The 360 day time averaged upper limits are 0.0002 gamma/sq cm-s x 0.0001 gamma/sq cm-s for both lines.
Geldzahler, B. J.↗
Very high resolution observations of the radio source in the supernova remnant G127.1+0.5
The results of recent very long baseline interferometry of G127.11+0.54 at 10.65 GHz reveal a core dual 'jet' structure. The morphology and physical properties of the compact source are similar to those of SS 433. The combined data from various studies of this object suggest that G127.11+0.54 may be the stellar remnant of the supernova event which also produced the supernova remnant G127.1+0.5.
Geldzahler, B. J.↗
Very high-resolution observations of compact radio sources in the directions of supernova remnants
Compact radio sources whose positions lie within the outlines of supernova remnants may be the stellar remnants of supernova explosions and, if they are related to the supernova remnants, may be used to explore the nature of any morphological connection between the Galactic and extragalactic radio sources. Three such compact sources, G 127.11+0.54, CL 4, and 2051+433, have been observed at 10.65 GHz with an array of very long baseline interferometers having elements in the USA and West Germany. The radio source 2051+433 was also observed briefly at 5.01 GHz. The measured size of CL 4 at 10.65 GHz is about 0.0005 arcsec and seems to be dominated by the effects of interstellar scattering. No fringes were seen in 2051+433, and results indicate there is no compact component of 2051+433 smaller than 0.001 arcsec radiating at 10.65 GHz above a level of about 50 mJy. The possibility is presented that G 127.11+0.54 is a Galactic object. It is found to consist of two components separated by about 0.002 arcsec and oriented perpendicular to both the radio bridge of the supernova remnant G 127.1+0.5 and the underlying optical image. G 127.11+0.54, if Galactic, lies at the extreme low-luminosity end of an apparent continuum of Galactic and extragalactic compact radio source luminosities.
Geldzahler, B. J.↗
Sco X-1 - A galactic radio source with an extragalactic radio morphology
VLA observations of radio emissions at 1465 and 4885 MHz, of Sco X-1 confirm the existence of a colinear triple structure. Evidence that the three components of Sco X-1 are physically associated is presented, including the morphology, spectrum, variability, volume emissivity and magnetic field strength. The possibility of a physical phenomenon occurring in Sco X-1 similar to that occurring in extragalactic radio sources is discussed, and two galactic sources are found having extended emission similar to that in extragalactic objects. The extended structure of Sco X-1 is also observed to be similar to that of the hot spots in luminous extragalactic sources, and a radio source 20 arcmin from Sco X-1 is found to lie nearly along the radio axis formed by the components of Sco X-1.
Geldzahler, B. J.↗
Very high resolution observations of SS433 at 10.65 GHz
Observations of SS433 made on June 12, 1979, from West Germany, Massachusetts, and West Virginia are discussed. It is noted that SS433 did not show fringes on any baseline although all the calibration sources were seen at their expected strengths. The measured total flux density of SS433 was found to be approximately 0.5 Jy, consistent with previous observations. The source was observed by on-offs at each telescope, which indicates that they were all pointed properly during the observations. The absence of fringes is not attributed to poor observing conditions or instrumental difficulties. It is concluded that if all the 10.65 GHz radiation emanates from a single component, then that component is at least 0.005 arcsec (approximately 10 to the 14th cm) in size. The measurements made on more sensitive intercontinental baselines indicate that there is no component of SS433 smaller than 0.001 arcsec emitting 10.65 GHz radiation above a level of 50 mJy.
Geldzahler, B. J.↗
VLBI observations of SS 433 at 3.6 and 13 centimeters
SS 433 was detected and partially resolved at 2290 MHz on baselines with fringe spacings of 1.4, 0.1, and 0.003 arcsec. It was also detected at 8420 MHz on a baseline with a fringe spacing of 0.009 arcsec. Simple models of the source, consistent with the limited data, have elongated structures greater than 0.1 arcsec in size with position angles in 1979 May that were within about 10 deg of the position angle of the apparent bulges of the supernova remnant W50. The data also imply that the source contains a core less than 0.002 arcsec in size with a brightness temperature greater than 10 to the 9th K. The bright core and aligned structures that seem to be present in SS 433 and W50 resemble the structures seen in powerful extragalactic radio sources which are many orders of magnitude larger.
Walker, R. C.↗
High resolution observations of the compact radio sources CL4, Cygnus X-3, and the Galactic Center
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Geldzahler, B. J.↗
A compact radio source in the nucleus of M82
The brightest compact radio source in the nucleus of M82 has a linear diameter of about 0.02 parsecs (25 light-days). On the basis of this small size and energy considerations, it seems that this source is probably not a supernova remnant, but is similar in nature to the compact radio sources found in the nuclei of spiral and elliptical galaxies, Seyfert galaxies, radio galaxies, and in quasi-stellar objects.
Geldzahler, B. J.↗
The small radio source at the galactic center
Very-long-baseline interferometer observations show that the compact radio source at the Galactic Center has dimensions of approximately 200 AU and that about 25% of the emission comes from a region only 10 AU across. There is no evidence for any expansion or contraction of this compact source, with a velocity of at least a few tens of kilometers per second.
Kellermann, K. I.↗