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Mcclintock, J. E.

Publications and source records attributed to Mcclintock, J. E..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Simultaneous X-ray and optical observations of the 7.7 second X-ray pulsar 4U 1626-67

Simultaneous X-ray and optical observations of the 7.7-s X-ray pulsar 4U 1626-67, obtained during May 29-31, 1978, reveal the presence of (1) intense, correlated optical and X-ray flares and (2) 7.7-s optical pulsations which agree in phase with the 1-3 keV X-ray pulsations to within 0.5 s (two standard deviations) and which agree in period to within 0.001 s (one standard deviation). From these data it is concluded that a substantial fraction (a minimum of 8%) and possibly all of the optical emission is produced from within approximately 0.5 light sec or 1.5 x 10 to the 10th cm of the neutron star. Furthermore, the data rule out the possibility that this optical emission comes from the X-ray heated surface of a degenerate or nondegenerate dwarf companion. It most likely comes from an accretion disk.

Mcclintock, J. E.↗
NASA NTRS1979

A spectroscopic study of the optical counterparts of three X-ray bursters

One of the major puzzles in galactic X-ray astronomy is the nature of the galactic bulge sources in general and the X-ray burst sources in particular. The answer to this puzzle is likely to come from studies of the faint blue optical counterparts which have been identified with several of these sources. As part of such a study, some results of a detailed investigation of the spectroscopic properties of the optical counterparts to three X-ray bursters - 4U 1735-44, 4U 1636-53, and MXB 1659-29.

Canizares, C. R.↗
NASA NTRS1979

Optical studies of the Seyfert 2 X-ray galaxy NGC 2110

Spectrophotometry of the nucleus of the X-ray galaxy NGC2110 shows a typical Seyfert Type 2 spectrum with a strong galactic continuum. The widths of the forbidden lines are about 360 km/s (FWHM), H-beta being somewhat broader. The moderate Balmer decrement implies that the interstellar reddening is approximately 2.1 mag. The average electron density and temperature in the line-emitting region are approximately 300 per cu cm and 35,000 K, respectively. From measurements of the nebulium line, it is found that the extent of the nucleus measured along the major axis of the galaxy is about 10 arcsec (2100 pc) and the full range of gas velocities is about 700 km/s. A direct plate is discussed which shows faint spirallike features in NGC2110, a galaxy currently classified as elliptical. NGC2110 is a member of a new class (about 5 members) of very nearby (cz less than 2500 km/s) X-ray galaxies. Bradt et al. (1978) tentatively concluded that they are Seyfert Type 2 galaxies. This conclusion is supported, and it is shown that this is not inconsistent with the narrowness (less than 500 km/s FWHM) of their emission line.

Mcclintock, J. E.↗
NASA NTRS1979

A 3-s delay in an optical burst from X-ray burst source MXB1735-44

Analysis of the arrival times of X-ray and optical bursts from the X-ray burst source MXB1735-44 shows that the onset of one optical burst was delayed 2.8 sec with respect to the X-ray burst. Observations of the pulses are accurate to less than or equal to five ms. The delay in the optical pulse may be attributed to light travel time in the system and/or the time needed to reprocess X-rays into light.

Mcclintock, J. E.↗
NASA NTRS1978

NGC 2110 - An X-ray/radio galaxy with elliptical morphology

The detection of X-ray emission from NGC 2110, a narrow-emission-line galaxy of apparently elliptical morphology, is reported. A relatively hard 2-11-keV energy spectrum with an index of 0.1 + or - 0.3 is obtained, and the X-ray luminosity in this energy band is shown to be 1.2 x 10 to the 43rd erg/s for the redshift distance of 43 Mpc. Optical and radio observations are discussed which indicate a galactocentric redshift of approximately 0.0071, a resolved nonstellar optical nucleus about 4 arcsec in extent, Seyfert type 2 emission lines from the nucleus, and a nonthermal radio source located 3.0 arcsec from the position of the optical nucleus. No evidence is found for X-ray source variability in NGC 2110. It is suggested that the four to seven known X-ray-emitting high-excitation narrow-emission-line galaxies appear to be nearby examples of the Seyfert type 2 phenomenon and that the elliptical morphology of NGC 2110, if confirmed, may be unique among known Seyfert galaxies.

Bradt, H. V.↗
NASA NTRS1978

Optical studies of the X-ray globular cluster NGC 6624

Photographic, photometric, and spectroscopic studies of the core of the globular cluster NGC 6624 have been undertaken with the aim of obtaining some evidence regarding the location and nature of the associated X-ray source 3U 1820-30. The studies include an extended simultaneous observation with the SAS 3 satellite, which was carried out to search (unsuccessfully) for optical emission during X-ray bursts. All the results reported are shown to be negative, but serve to set some constraints on the source properties. The photometric results are used to derive a core radius of 5.0 + or - 0.5 arcsec (0.19 + or 0.02 pc at 8 kpc) and a central density of 110,000 solar masses per cu pc for the cluster. It is found that NGC 6624 is one of the most centrally dense globular clusters but otherwise normal and that the colors and spectrum of the nucleus are the same as those of the cluster as a whole. An X-ray source similar to HZ Her at maximum light is ruled out.

Canizares, C. R.↗
NASA NTRS1978

Discovery of optical bursts from an X-ray burst source, MXB1735-44

The optical counterpart of 4U 1735-44, X-ray burst source MXB 1735-44, was studied with the 1.5-m telescope at Cerro Tololo, and by SAS 3, during the period between June 1 and 3, 1978. Explanations for the optical activity are discussed in terms of accretion instabilities onto a neutron star, or thermonuclear flashes on the neutron star itself. Attention is given to the timing of the bursts, which indicate that the burst source probably is located in a region within 1-2 light seconds from the X-ray source. In the binary case, it is noted that the optical emission is probably removed from the X-ray heated stellar atmosphere of the possible companion.

Grindlay, J. E.↗
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 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

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

Discovery of a 272 second periodic variation in the X-ray source GX 304-1

Observations of GX 304-1 (3U 1258-61) performed with the SAS-3 satellite revealed regular X-ray pulsations with a period of 272 s. Average pulse profiles, derived from 7 days of observation, are presented in four energy intervals covering the range 1-19 keV. The pulses are basically characterized by a single broad peak, and the amount of modulation decreases rapidly with increasing energy. The pulse arrival times are analyzed for effects of possible orbital motion of the X-ray star, and significant constraints are placed on the orbital parameters. For example, if it is established that the companion is an early-type star of at least 5 solar masses, then the orbital period is likely to be greater than about 15 days. Three 100-s flares were observed during which the source intensity rose by a factor of 4 in approximately 10 s.

Mcclintock, J. E.↗
NASA NTRS1976

Discovery of X-ray bursts from several sources near the galactic centre

Three X-ray burst sources have been discovered within approximately 0.5 deg of the Galactic center. All bursts from this region show a low-energy cutoff near 3 keV. The bursts from MXB 1743-29 show distinct double and triple peaks; the time interval between bursts from this source was about 1.46 day. The intervals between bursts from MXB 1742-29 and MXB 1743-28 were approximately 0.55 day and 10 min respectively. Steady emission from this collection of burst sources could account for most of the flux from the apparently extended X-ray source GCX (3U 1743-29).

Lewin, W. H. G.↗
NASA NTRS1976

Observations of two X-ray flares and the nearby source MX 1716-31

Observations of the X-ray source MX 1716-31 by detectors aboard OSO-7 are described. During the study of the MX 1716-31 data, an X-ray flare was discovered which was probably associated with the source. The flare had a total duration of about 10 minutes and reached a peak intensity twice that of the Crab Nebula in the 3-10-keV range. A search for similar events elsewhere turned up one other flare with a position inconsistent with MX 1716-31. Those features of both flare events which are relevant for comparison with other short-lived X-ray phenomena are discussed.

Markert, T. H.↗
NASA NTRS1976

Radius of the Vela pulsar

Lasker (1976) has proposed to identify a B roughly equals 23.7 mag star as thermal radiation from the hot neutron star associated with the Vela pulsar. It is shown that this identification, if correct, together with existing X-ray surveys of the Vela supernova remnant, requires that the radius of this pulsar certainly exceed 45 km, and probably 95 km.

Greenstein, G.↗
NASA NTRS1976

High-energy X-ray observations of the southern sky

Results are reported for high-energy (above 17 keV) balloon-borne X-ray observations in the southern sky which detected at least five sources that produced X-ray counts above background with a significance of four or more standard deviations. The probable sources observed include GX 301-2 (3U 1223-62), GX 1+4 (3U 1728-24), GX 5-1 (3U 1758-25), GX 3+1 (3U 1744-26), and GX 331-1. It is noted that some or all of the flux attributed to GX 5-1 might be due to 3U 1820-30 and that GX 3+1 was not completely resolved from GX 1+4. Energy spectra are given for each source along with upper limits to periodic fluctuations of the detected fluxes in the frequency range from 0.01 to 100 Hz. A possible observation of a flux from the eclipsing binary source 3U 1700-37 is discussed.

Ricker, G. R.↗