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Jauncey, D. L.

Publications and source records attributed to Jauncey, D. L..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

(abstract) A Relativistically Expanding Radio Source Associated with GRO J1655-40

GRO J1655-40 was discovered as a new, bright X-ray source with the BATSE detector of the Gamma Ray Observatory (GRO) on July 27, 1994. During the subsequent radio outburst we completed VLBI synthesis imaging observations at a frequency of 2.29 GHz. An unprecedented angular motion of 65+/- mas per day was reported between two components of complex and disparate morphology ?? The separation rate indicates that the two components were at zero separation near the onset of the radio flare. Similar to the recently reported GRS 1915+105, it seems that the motion of material ejected from a stellar mass compact object with at least a mildly relativistic velocity may explain the observed radio structural changes in GRO J1655-40. The two-week delay between the X-ray outburst and the production of radio components may indicate that the X-rays were produced by a super-critical accretion process onto the compact member of this stellar binary system. This process inhibited or smothered the ejection of radio components until the accretion disk stabilized.

X-ray sources Gamma Ray Observatory GRO radio outb↗
NASA NTRS1994

A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere

We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.

Russell, J. L.↗
NASA NTRS1994

Centaurus A, the core of the problem

The bright, peculiar elliptical galaxy Centaurus A (NGC 5128, PKS 1322-427) was one of the first extragalactic radio sources to be optically identified (Bolton et al. 1949). At a distance of 4 Mpc, Centaurus A is the closest active radio galaxy and affords the highest linear imaging resolution (1 mas approximately equal to 0.02 pc) and hence the best prospects for studying an active nucleus close to the central radio source. We present the results of multi-epoch, 8.4-GHz, very long baseline interferometry (VLBI), imaging observations of the nucleus made over the past three years. The nucleus possesses a core-jet structure where the inner portion of the jet shows apparent linear motion with a velocity substantially less than the speed of light.

Tingay, S. J.↗
NASA NTRS1992

A radio optical reference frame. III - Additional radio and optical positions in the Southern Hemisphere

Radio and optical positions are presented for southern hemisphere extragalactic sources from the Parkes 2.7 GHz survey. Sixty-one sources were observed with Mark III VLBI at 8.4 GHz between Tidbinbilla, Australia, and Hartebeesthoek, South Africa. The results presented are part of the effort to establish a global reference frame of 400 extragalactic radio sources. Radio positions with about 10 milliarcsec errors have been estimated for 39 sources not previously in the present radio reference frame catalog, and provisional positions were obtained for two additional sources, bringing the total number of catalog sources to 276. The principal source of error is the uncalibrated ionosphere. Of the remaining sources five were completely undetected, six were either too faint or too resolved, and nine had previous catalog positions. Optical positions on the FK5 system have also been measured for four southern sources using prime focus plates from the Anglo-Australian 4 m telescope with an accuracy of 0.06 arcsec. This raises to 40 the number of radio sources with accurately measured positions for their optical counterparts.

Russell, J. L.↗
NASA NTRS1991

An unusually strong Einstein ring in the radio source PKS1830 - 211

High-resolution radio images of PKS1830 - 211 are obtained to study the possibility that the double structure is a gravitationally lensed object. The VLBI observations, taken from interferometric radiotelescope networks, reveal an elliptical ring that connects two bright spots of similar composition. Because the lens and the lensed object are closely aligned, and because of the structure of the two spots, the source is concluded to be a radio Einstein ring. The source is found to be close to the galactic plane, and the lens and the lensed object are extragalactic. The source is also found to be unusually bright, suggesting that it is aligned with a bright background source or amplified by some mechanism related to a source that is not so bright.

Jauncey, D. L.↗
NASA NTRS1988

Supernova 1987A - A radiosphere resolved with VLBI five days after the neutrino burst

The results of VLBI observations of SN1987A are reported. No emission from the supernova above a level of about 20 percent of the supernova's total flux density was detected, although signals were detected from two calibrator sources with amplitudes roughly equal to those determined in earlier VLBI observations. It is inferred that the supernova's radiosphere was resolved, and a lower bound on the radiosphere's radius of 2.2 mas is estimated from an epoch 5.2 days after the neutrino burst. Given the photometric data from the supernova, a distance to the LMC of 50 + or - 5 kpc, and an apparent expansion velocity that varied systematically with time from 18,000-16,000 km/s, as estimated from the blue-shifted H-alpha absorption lines on the days preceding the observations, it is concluded that 5.2 days after the neutrino burst the supernova's radiosphere was at least 2.5 times larger than the inferred blackbody photosphere, and at least as large as the H-alpha line-forming region.

Jauncey, D. L.↗
NASA NTRS1988

The southern hemisphere VLBI experiment (SHEVE)

Six radio telescopes were operated as the first southern hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 Ghz. This array produced VLBI images of 28 southern hemisphere radio sources, high accuracy VLBI geodesy between southern hemisphere sites, and sub-arcsecond radio astrometry of celestial sources south of declination -45 degrees. This paper discusses only the astrophysical aspects of the experiment.

Preston, R. A.↗
NASA NTRS1988

Radio observations of SN 1987A

The study of radio emission from SN 1987A after the neutrino burst is reviewed. The observed maximum flux density of the burst at radio wavelengths was about 140 mJy and occurred at 1.4 GHz. The radio light curves for SN 1987A at four frequencies are compared with data for SN 1979C and SN 1980K. VLBI observations of SN 1987A at 2.3 GHz and other radio monitoring programs are examined.

Bartel, N.↗
NASA NTRS1986

A radio nebula associated with Circinus X-1

An investigation of the variable source Circinus X-1 is reported that reveals that this eccentric double-star system is embedded in a nebula of steady radio emission extending over several parsecs, orders of magnitude larger than the binary stellar system responsible for the fluctuating component of emission. This is in marked constrast to most X-ray binaries, where an envelope of radio emission in conspicuously absent. There are difficulties in explaining the emission, but analogies with SS433 and the Crab nebula suggest possible models.

Haynes, R. F.↗
NASA NTRS1986

Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. IV - Seventeen sources

VLBI measurements of time delay and delay rate at 2.29 and 8.42 GHz on baselines of 10,000 km have been used to determine the positions of the milliarcsecond nuclei in 17 extragalactic radio sources with estimated accuracies of 0.1 to 0.3 arcsec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. In addition, slightly improved positions are presented for 101 sources originally reported by Morabito et al. (1983). Arcsecond positions have now been determined for 836 sources.

Morabito, D. D.↗
NASA NTRS1985

A VLBI survey at 2.29 GHz

VLBI observations at 2.29 GHz with fringe spacings of about 3 milliarcsec have been performed on 1398 radio sources spread over the entire sky. 917 sources were detected, including 93 percent of the identified BL Lacertae objects, 86 percent of the quasars, and 36 percent of the galaxies. The resulting catalog of compact radio sources is useful for various astrophysical studies and in the formation of VLBI celestial reference frames.

Preston, R. A.↗
NASA NTRS1985

A VLBI survey at 2.29 GHz

The Deep Space Network (DSN) is establishing a high-accuracy VLBI celestial reference frame. The results of a search for suitable radio sources to be used in constructing this frame are given. The VLBI observations using DSN baselines at 2.29 GHz with fringe spacings of about 3 milliarcseconds have been performed on 1398 radio sources spread over the entire sky. Of those, 917 sources were detected including 93% of the identifed BL Lacertae objects, 86% of Quasars and 36% of galaxies. The resulting catalog of compact radio sources is also useful for various astrophysical studies and in the formation of VLBI celestial reference frames.

Morabito, D. D.↗
NASA NTRS1985

Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. III - 74 sources

VLBI measurements at 2290 and 8420 MHz on baselines of 10,000 km have been used to determine the positions of the milliarcsecond nuclei in 74 extragalactic radio sources. Estimated accuracies range from 0.1 to 4.3 arcsec in both right ascension and declination with typical accuracies of about 0.3 arcsec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. Arcsecond positions have been determined for 819 sources. These positions are presently being used to identify optical counterparts in the southern hemisphere.

Morabito, D. D.↗
NASA NTRS1985

Arcsecond Positions for Milliarcsecond VLBI Nuclei of Extragalactic Radio Sources. Part 3: 74 Sources

VLBI measurements at 2290 MHz and 8420 MHz on baselines of 10,000 km between Deep Space Network stations have been used to determine the positions of the milliarcsecond nuclei in 74 extragalactic radio sources. Estimated accuracies range from 0.1 sec. to 4, 3 sec. in both right ascension and declination with typical accuracies of approx. 0.3 sec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. Arcsecond positions have now been determined for 819 sources. These positions are presently being used to identify optical counterparts in the Southern Hemisphere.

Morabito, D. D.↗
NASA NTRS1984

The radio and optical identification of Circinus X-1

VLBI and CCD astrometry is presented which establishes the coincidence of the X-ray and radio object Cir X-1 with an object lying about one arcsec south of the object 'L' of Whelan et al. (1977), a conclusion reached previously by Argue and Sullivan (1982). The question whether the object L has any physical connection with Cir X-1 cannot yet be definitely answered.

Argue, A. N.↗
NASA NTRS1984

Arcsecond Positions for Milliarcsecond VLBI Nuclei of Extragalactic Radio Sources, Part 2: 207 Sources

Very long base interferometry measurements of time delay and fringe frequency at 2.29 GHz on baselines of 10,000 km between Deep Space Network stations were used to determine the positions of the milliarcsecond nuclei in 207 extragalactic radio sources. Estimated accuracies generally range from approximately 0.1 to approximately 1.0, in both right ascension and declination, with all sources having uncertainties 4" in both coordinates. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. Arcsecond positions are now determined for 752 of these sources. Arcsecond positions serve as a useful starting point in the construction of high-precision VLBI reference frames and are also important for unambiguous determination of optical counterparts to compact radio sources.

Morabito, D. D.↗
NASA NTRS1983

Results of the Australian geodetic VLBI experiment

The 250-2500 km baseline vectors between radio telescopes located at Tidbinbilla (DSS43) near Canberra, Parkes, Fleurs (X3) near Sydney, Hobart and Alice Springs were determined from radio interferometric observations of extragalactic sources. The observations were made during two 24-hour sessions on 26 April and 3 May 1982, and one 12-hour night-time session on 28 April 1982. The 275 km Tidbinbilla - Parkes baseline was measured with an accuracy of plus or minus 6 cm. The remaining baselines were measured with accuracies ranging from 15 cm to 6 m. The higher accuracies were achieved for the better instrumented sites of Tidbinbilla, Parkes and Fleurs. The data reduction technique and results of the experiment are discussed.

Harvey, B. R.↗