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Jernigan, J. G.

Publications and source records attributed to Jernigan, J. G..

At least 37 records · Page 2
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NASA NTRS1978

An energy-dependent map of the X-ray emission of the Perseus cluster

Results are discussed for X-ray scans of the Perseus cluster with the SAS 3 slat detectors. Counting rates in two broadband channels (1.5 to 5.5 keV and 5.5 to 15.5 keV) are compared as a function of the instrument scan angle measured from the center of emission, and it is found that the emission in the higher energy range is broader in extent. Tests for a systematic energy-dependent error in the background demonstrate that the discovered energy dependence of the Perseus cluster emission is valid. Iron line emission is determined by two methods, various models are fitted to the data, and the total cluster emission in the two energy ranges is computed. The iron line emission is determined to be 0.003 photon/sq cm per sec. It is concluded that the diffuse emission increases in the range from 1.5 to 15.5 keV within the bounds of a model involving a point source with a radius not exceeding about 3 arcmin plus a diffuse source.

Ulmer, M. P.↗
NASA NTRS1978

Positions of galactic X-ray sources - At longitudes /l-II/ of 55-320 deg

Rotating modulation collimeter detectors on the SAS-3 X-ray observatory were used to supply precise (20-40 sec) positional data on 10 galactic X-ray sources in the l super II region between 55 and 320 deg. It is noted that the position for 2S0114+650 has led to the discovery of an optical counterpart. Attention is given to the temperature dependence of the experiments, and it is found that position measurements made at low temperatures are consistent with those obtained at normal (0 C) temperatures. Positions, error radii, and intensities (2-11 keV) are listed for each of the ten sources.

Dower, R. G.↗
NASA NTRS1978

Searches for correlated X-ray and radio emission from X-ray burst sources

The NRAO Green Bank interferometer has been used to monitor MXB 1730-335 and MXB 1837+05 during periods when 68 X-ray bursts were detected by X-ray observations. No significant radio emission was detected from these objects, or from MXB 1820-30 and MXB 1906+00, which emitted no bursts throughout the simultaneous observations. The data place upper limits on radio emission from these objects in the 2695 and 8085 MHz bands.

Johnson, H. M.↗
NASA NTRS1978

Positions of galactic X-ray sources with l/II/ between -20 deg and +6 deg

The precise positions of nine X-ray sources in the vicinity of the galactic center are reported. The data were obtained as part of the comprehensive survey of the galactic plane performed with the rotating modulation collimator detectors on the SAS-3 X-ray observatory. The sources include the binary X-ray source 4U 1700-37 which has a well established optical counterpart that lies 7 sec from the reported position. The other sources GX 349+2, 4U 1702-42, 4U 1705-44, MX 1716-31, A 1742-294, 4U 1755-33, GX 5-1, and 2S 1803-245 lack established counterparts in other wavelengths. The obtained position for GX 5-1 adds confidence to the radio counterpart proposed by Braes et al. (1972). The reported position for 4U 1755-33 excludes the optical counterpart proposed by Jones et al. (1974).

Jernigan, J. G.↗
NASA NTRS1978

On two new X-ray sources in the SMC and the high luminosities of the Magellanic X-ray sources

The discovery of two new X-ray sources, SMC X-2 and SMC X-3, in the Small Magellanic Cloud is reported. They have hard spectra, and their luminosities in the energy range 2-11 keV are 1.0 and 0.7 by 10 to the 38th power erg/sq cm per sec, respectively. It is shown that the luminosity distribution of the known Magellanic X-ray sources, which are now nine in number, is shifted toward higher luminosities with respect to that of similar sources in the Galaxy, and that the cause of the shift is probably an underabundance of heavy elements in the material accreted by the X-ray sources.

Clark, G.↗
NASA NTRS1978

Compact and diffuse X-ray sources in the core of the Perseus cluster /Abell 426/

Data on the X-ray structure of the Perseus cluster of galaxies in the energy range from 2 to 10 keV are analyzed which were obtained during a 12-day observation with the rotating modulation collimator aboard SAS 3. In particular, the nature of the compact X-ray source coincident with NGC 1275 is examined. The data are shown to confirm the presence of a diffuse region of X-ray emission surrounding the nucleus of NGC 1275; it is found that a model which also includes a point source at the nucleus is consistent with the data if the point contribution is no larger than 20% of the X-ray flux detected within 3 to 5 arcmin of the galaxy. The results suggest that NGC 1275 may have accreted a large amount of gas from the intracluster medium and that the flux from the possible point source is consistent with a synchro/Compton model.

Helmken, H.↗
NASA NTRS1978

SAS 3 observations of two X-ray transient events with precursors

SAS 3 has observed two unusual fast transient X-ray events from different sources, one lasting about 150 s and one, approximately 1500 s. Both events were preceded by precursor pulses which lasted a few seconds and which rose and fell in less than 0.4 s. The precursors were separated from the 'main' events by several seconds, during which no X-rays were detected. There are similarities between the two main events and X-ray bursts in both their temporal and spectral evolution. The spectra of the main events started out much softer than the spectra of the precursors, became harder as they approached maximum intensity, and softened as they decayed. In the 1500-s event, X-rays with energies greater than 10 keV were delayed by about 80 s compared with 1.5-6-keV X-rays. A blackbody fit to the spectral data of the main event of approximately 1500-s duration gives a maximum temperature of 29 million K and a radius for the emitting region of at least about 9 km (at a distance of 10 kpc); this is similar to the temperature and sizes found for several X-ray burst sources.

Hoffman, J. A.↗
NASA NTRS1978

Positions of galactic X-ray sources - l/II/ between 320 and 340 deg

The precise (20-40 sec) positions of seven X-ray sources in the celestial region corresponding to the galactic longitude range from 320 to 340 deg are reported. The sources include a recurrent transient X-ray source (MX1608-52) and a source 2S1553-542 coincident with a gamma-ray source within the given errors of position. The positions reported reduce the previously reported areas of the error region for six of the sources by factors ranging from 10 to 100. The presented results add confidence to the proposed radio candidates for 4U1624-49 and 4U1642-45 considered by Sanduleak and Dolan (1974) and Seaquist (1977).

Apparao, K. M. V.↗
NASA NTRS1978

Discovery of an X-ray QSO

The discovery of X-ray QSO MR2251-178 at a distance of 410 Mpc is reported. The observations are based on signals (2-11 keV) from NRAO's Very Large Array (VLA) radio telescope and from two independent rotating modulation collimators (RMC). Coordinates are given and positional identification with X-ray source 2A2251-179 is made. Examination of POSS plates and redshift has given rise to speculation that MR2251-178 could actually be a Seyfert galaxy; but its high luminosity would tend to support the contention that it is, indeed, a QSO.

Ricker, G. R.↗
NASA NTRS1977

Positions of galactic X-ray sources - Galactic latitudes between zero and 20 deg

Precise (to 20 or 25 arcsec) positions of six X-ray sources located in the galactic bulge are reported which were obtained as part of a survey of the galactic plane performed with the SAS-3 rotating modulation collimators. The sources include GX1+4, GX9+9, GX3+1, GX9+1, GX13+1, and GX17+2. The error radii and X-ray intensities (2 to 11 keV) determined for the sources are also presented along with finding charts and proposed optical and radio counterparts. The results are compared with those of previous satellite and sounding-rocket experiments. The status of each source with respect to optical or radio identifications is briefly discussed.

Doxsey, R. E.↗
NASA NTRS1977

Optical candidates for two X-ray bursters and an X-ray pulsar

Faint blue stars are suggested as the optical counterparts of the X-ray bursters 4U (MXB) 1636-53 and 4U (MXB) 1735-44 as well as the 7-sec X-ray pulsar 4U 1626-67. The candidate stars have large UV excesses and were discovered well within the 20- and 30-arcsec error radii determined with the rotating modulation collimator aboard SAS 3. Photographic observations and photoelectric photometry of the candidate stars are discussed. It is shown that the candidates for 4U 1626-67 and 4U 1636-53 lie further from the reddened-supergiant or main sequence than any known X-ray source counterparts and have colors that are inconsistent with those of a reddened normal star, while the candidate for 4U 1735-44 has the colors of both Sco X-1 and a late O or BO star suffering about 1 mag of extinction.

Mcclintock, J. E.↗
NASA NTRS1977

Positions of three X-ray burst sources

Precise (20-30 arcsec) positions are reported for three steady X-ray sources that have been identified recently as X-ray burst sources: 4U (MXB) 1636-53, 4U 1728-33 (MXB 1728-34), and 4U (MXB) 1735-44. The positions were derived from data obtained with the SAS 3 rotating modulation collimators during a survey of the galactic plane. Possible optical counterparts are noted.

Jernigan, J. G.↗
NASA NTRS1977

X-ray and radio observations of the structure of Abell 478

The complex X-ray and radio structures of the cluster of galaxies Abell 478 have been observed in the 2-11-keV energy band by the rotating modulation collimators on the SAS-3 X-ray observatory and at 1415 MHz by the Westerbork synthesis radio telescope. The X-ray data imply an extended source (X-ray luminosity of the order of 10 to the 45th power erg/s) and are consistent with the presence of a coincident pointlike source X-ray luminosity of the order of 10 to the 45th power erg/s. The X-ray source position is also coincident with a cD radio galaxy at the core of the cluster.

Schnopper, H. W.↗
NASA NTRS1977

Discovery of a 7.68 second X-ray periodicity in 3U 1626-67

SAS-3 observations of the X-ray source 3U 1626-67 have revealed the presence of a stable 7.68-sec pulse period. This source was selected for study because of its hard X-ray spectrum. The compilation of source spectra used in the selection process is also presented. Pulse arrival times are analyzed for effects of possible binary orbital motion. Upper limits to the projected orbital radius are obtained which tend to exclude orbital periods in the range from about 0.5 to 35 days. Binary systems with either a very long orbit (at least 175 days) or a very short orbit (no more than about 0.3 day) are most probable

Rappaport, S.↗
NASA NTRS1977

Positions of galactic X-ray sources - Galactic longitude between 20 and 55 deg

Precise positions, determined with data from the SAS-3 X-ray observatory, are presented for eight galactic plane X-ray sources (Aql X-1, Ser X-1, 3U 1956+11, 3U 1822-00, 3U 1915-05, A 1845-02, A 1850-08, A 1905+00). Error radii for the positions range from 20 to 50 arc s. Previously proposed optical identifications of three of the sources (Ser X-1, 3U 1956+11, A 1850-08) are supported by these results. Three (Ser X-1, A 1905+00, 3U 1915-05) have been identified as X-ray burst sources.

Doxsey, R. E.↗
NASA NTRS1977

On the optical identifications of five X-ray sources

The data from a recently completed survey of the galactic plane with the SAS-3 modulation collimators provide precise (20 to 60 arcsec) celestial positions of galactic X-ray sources. Preliminary positions of 60-arcsec precision are reported for five sources. One of these led to the identification of the star, Gamma Cas, as an X-ray source, and the others lend substantial confidence to previously proposed optical identifications: 3U 0352+30 = X Per, 3U 1145-61 = HEN 715, GX301-2 = WRA977, and GX304-1 = MMV star. These identifications seem to establish the existence of a previously suggested class of Be-star X-ray emitters.

Bradt, H. V.↗
NASA NTRS1976

The transient X-ray source A0620-00 - Intensity variations and evidence for an 8 day periodicity

The X-ray intensity of the transient source A0620-00 has been measured frequently with the SAS-3 X-ray Observatory from August 8, 1975 to February 13, 1976. This brightest of all known X-ray transients shows intensity variations on a time scale of days superposed on a general decline. Intensity data for the period from January 7 to February 13, 1976, show evidence of an approximate 7.8-day periodicity that may be the result of binary motion.

Matilsky, T.↗