Engineering topics

Fabbiano, G.

Publications and source records attributed to Fabbiano, G..

At least 73 records · Page 4

NASA NTRS1985

Detailed X-ray observations of M83

X-ray observation of M83 with the Einstein Observatory indicates an extent and shape for this emission that are comparable to those in the blue band, although the inner 2-arcmin region shows a relative X-ray excess that may be accounted for by a clustering of bulge-type X-ray sources in the inner region of the plane of the galaxy. A lack of correlation in high resolution X-ray observations is noted between X-ray emission and the spiral arm pattern, suggesting that most of the X-ray emission from the plane of M83 is due to unresolved sources, belonging to the 'smooth' disk population, whose ages are in the 100 million-1 billion year range. Attention is given to six bright sources in the plane and nuclear region of M83, whose high X-ray luminosities suggest that they are close accreting binaries.

Trinchieri, G.↗

NASA NTRS1984

The complex X-ray emission of NGC 253

High-resolution X-ray observations of the starburst galaxy NGC 253 with the Einstein Observatory show that there are at least four components to its X-ray emission. Eight bright point-like sources were detected. Diffuse emission is visible in the inner disk of NGC 253. A more intense emission region is associated with the nuclear region and with an extension along the southern portion of the minor axis. This last component, in particular, suggests the presence of shock-heated gas associated with outflow from the starburst nucleus. A siimlar feature was seen in the X-ray emission of M82. A comparison between the nuclear regions of NGC 253, M82, and the Milky Way suggests an excess of X-ray emission in the nucleus of M82.

Fabbiano, G.↗

NASA NTRS1984

X-ray observations of spiral galaxies. I - Integrated properties

The results of X-ray observations carried out with the Einstein satellite of 14 nearby field spiral and irregular galaxies are reported. The integrated properties of the galaxies are examined in the luminosity range from 10 to the 38th and 10 to the 40th ergs per sec at 0.5-3.0 keV. It is found that the X-ray luminosities of the galaxies are correlated with both the optical (blue) and the radio luminosities (1.4 GHz). The linear relationship found between the X-ray and the optical blue luminosities suggests a relationship to be between the X-ray luminosity and the stellar content of spiral galaxies exhibiting blue luminosities. On the basis of the correlations, it is proposed that most of the spiral galaxies are relatively young systems of not less than about 10 to the 9th years. Data obtained from the Einstein satellite and those of a previous investigation of the blue galaxies are compared in a table.

Fabbiano, G.↗

NASA NTRS1984

1-20 micron infrared photometry of 3CR radio galaxies

Seven emission-line radio galaxies in the wavelength range from 1 to 20 microns were observed in February 1983. Three broad emission-line galaxies (BLRGs 3C 109, 3C 234, and 3C 445), and four narrow emission-line radio galaxies (NLRGs 3C 98, 3C 198, 3C 223, and 3C 293) were found. The BLRGs showed strong infrared fluxes beyond 3.5 microns, with steep infrared slopes similar to optical slopes. In a comparison with earlier observational data it was found that two of the BLRGs are variable in the JHK filter range without a change of slope. The NLRGs showed strong excess at 10 microns and normal elliptical galaxy colors at JHK and L. Simple predictions based on type-2 Seyfert galaxies show that strong infrared excesses are absent.

Elvis, M.↗

NASA NTRS1984

X-ray and UV observations of two radio-bright quasars

The two quasars PKS 10004 + 13 (4C 13.41, V about equal to 15.2, z = 0.140) and PKS 0637 - 75 (V = 15.75, z = 0.651) were observed in December 1980 with IUE. Both were detected in the short-wavelength region. The present X-ray upper limit for PKS 1004 + 13 gives the lowest L-x/L-opt measured in quasars. PKS 0637 - 75 was observed nearly simultaneously with the Einstein Observatory and a spectrum obtained with the IPC. The UV and soft X-ray data have been combined and are discussed together with the optical and infrared data for both objects. The extreme L-x/L-opt ratio of PKS 1004 + 13 may be the result of an exceptionally large blackbody UV excess superposed on a power-law continuum of slope about 1.1. An alternative would be a large hydrogen column absorbing low-energy X-rays although this is unlikely. PKS 0637 - 75 shows no evidence for any UV excess. The two quasars seem to be at opposite ends of the degree of dominance of the UV spectrum by a blackbody component. The lack of a Lyman limit discontinuity in PKS 0637 - 75 at the redshift of an intervening galaxy implies that the optically detected, intervening hydrogen is ionized.

Elvis, M.↗

NASA NTRS1984

VV Puppis - The soft X-ray machine

The detection of soft and hard X rays from VV Pup is reported, and an orbital light curve is presented for both. The light curves are found to be in good agreement with the orbital light curve observed in the optical (Warner and Nather, 1972), suggesting that both X rays and optical light arise from the vicinity of a bright spot near one magnetic pole of the white dwarf. The radius of the soft X-ray-emitting bright spot is in the range 20-120 km, and its temperature is in the range (2-6) x 10 to the 5th K. The observed ratio of soft X-ray to hard X-ray fluxes is approximately 15, the highest of all the AM Her stars.

Patterson, J.↗

NASA NTRS1984

An X-ray survey of a complete sample of 3CR radio galaxies

The X-ray survey of the galaxies, 40 in all, was made with the Einstein Observatory. By comparing the distributions of X-ray luminosities, it is found that 3CR galaxies with double radio morphology (FR 2) and optical emission-line spectra tend to be the more powerful X-ray emitters, with broad-line galaxies at the top of the distribution. It is also found that the X-ray luminosity is strongly correlated with the 5 GHz radio nuclear luminosity. Through an analysis of the complete optical and radio sample with the Spearman partial rank correlation technique, it is determined that nuclear radio luminosity at 5 GHz is correlated with both total radio luminosity at 178 MHz and with galaxy optical luminosity. Other weaker correlations are found of the X-ray luminosity with the total radio luminosity at 178 MHz and the optical luminosity of the galaxy. The results are seen as underlining the importance of nuclear phenomena in radio galaxies and indicating a nuclear origin of their X-ray emission. In addition, it is found that the 3CR emission-line galaxies are similar to both Seyfert galaxies and quasars with double radio morphology in their X-ray properties, strongly reinforcing a unified picture of active nuclei.

Fabbiano, G.↗

NASA NTRS1984

The X-ray emission of normal spiral galaxies

Some results of an Einstein Observatory survey of X-ray emitting spiral galaxies are reported. The sources were normally 10-100 times further away than M31. Luminosities of 10 to the 38th to 10 to the 40th erg/sec were calculated and could have been generated by Pop I and Pop II binary systems, supernova remnants and small nuclear sources. Highly positive correlations were found among properties such as the integrated X-ray, optical and radio emissions. The data will also be compared with similar data from star burst and elliptical galaxies.

Fabbiano, G.↗

NASA NTRS1983

Star formation in blue galaxies. I - Ultraviolet, optical, and infrared observations of NGC 4214 and NGC 4670

NGC 4214 and NGC 4760 have been observed between 1150 A and 1950 A with the IUE satellite, and new infrared and optical broad-band photometry have been obtained. The spectra of both galaxies are dominated by O stars, and, in the spectrum of NGC 4214, the C IV 1550 A line exhibits a P Cygni profile indicative of hot stars with large mass-loss rates. Although the optical spectra of both galaxies are dominated by strong narrow emission lines, no strong emission lines are seen in the UV (the observed Ly-alpha flux is dominated by geocoronal emission). Both galaxies contain giant H II region complexes in which the energy (in particular, the H-beta luminosity and the ultraviolet continuum) is provided by several hundred O stars. The comparison of the observed UVOIR energy distributions with evolutionary population models indicates that the regions observed consist of young 'bursts' of star formation superposed on an underlying old population. The initial mass function for this epoch of star formation is constrained to be similar in slope to or flatter than the Salpeter function.

Geller, M. J.↗

NASA NTRS1983

X-ray observations of radio-jet galaxies

The possibility that the morphology of radio-galaxy jets may be influenced by interaction with X ray emitting gaseous halos led to a study of several jet galaxies with the Einstein Observatory. These observations carried out with the IPC had a high detection rate (5 out of the 6 radio galaxies observed). The X ray data for these objects are presented. The X ray luminosities lie between about 10 to the 42nd and 10 to the 45th erg/sec. The X ray emission was found to be extended for the two galaxies with the most counts. 3C130 and 3C449. Three of the detected galaxies are known to be associated with clusters and we suggest that 3C130 may also be associated with a cluster.

Miley, G. K.↗

NASA NTRS1983

Identification and properties of the M giant/X-ray system HD 154791 = 2A 1704+241

The Aerial V X-ray source 2A 1704+241 (= 4U 1700+24 = 3A 1703+241) is identified with the M3 II star HD 154791. The identification is based on a precise X-ray position determined by the HEAO 1 scanning modulation collimator and the Einstein Observatory imaging proportional counter, together with a spectrum measured by the International Ultraviolet Explorer. The ultraviolet spectrum shows strong emission of C IV 1550 A, N v 1238 A, and Mg II 2800 A, which is very unusual among M giants. This is the first X-ray detection of an M giant which has a completely normal optical spectrum. The X-ray luminosity reaches three orders of magnitude above the mean upper limit for the coronal X-ray flux from M giants. Although there is no direct evidence for a binary system, since radial velocity variations have not been observed, it is shown that a plausible neutron star binary model can be constructed.

Garcia, M.↗

NASA NTRS1983

X-ray and ultraviolet observations of extragalactic H II regions

The dwarf galaxies NGC 5204, NGC 5474, and NGC 5585 have been shown by Sandage and Tammann (1974) to be physically associated with M101 (distance 7.2 Mpc). The present investigation is concerned with observations of the dwarf galaxies in the M101 group conducted with the aid of the Einstein satellite. Upon detection of X-ray emission from NGC 5204, it was found possible to observe this galaxy also with the International Ultraviolet Explorer (IUE). It is now feasible to compare the predictions on the stellar population of the galaxy inferred from the X-ray data with a more direct measure concerning this population. It is found that the hypothesis regarding the responsibility of binary X-ray sources of Population I progenitors for most of the X-ray emission is strengthened by the IUE short-wavelength spectrum of NGC 5204.

Fabbiano, G.↗

NASA NTRS1983

X-ray observations of the Antennae /NGC 4038/39/

The merging galaxies NGC 4038/39 were observed with the imaging proportional counter onboard the Einstein Observatory on two separate occasions, 12 months apart. The X-ray map seems to follow the optical contour of the two 'heads', although a softer X-ray component with a different spatial distribution might be present. The harder component is interpreted as being due to the integrated emission of single X-ray sources (like SNRs and X-ray binaries) in the two interacting galaxies. A harder point-like source might also be present in the contact region. The softer component could be thermal emission of gas heated by the interaction between NGC 4038 and NGC 4039. Moreover, a significant difference was observed between the two exposures. An additional X-ray source is present in the first image, but not in the second. If this source is associated with the Antennae, it could be either a very bright X-ray transient or a recent, optically undetected supernova.

Fabbiano, G.↗

NASA NTRS1982

X-ray observations of AM Herculis in its low state

AM Her was observed with the Einstein Imaging Proportional Counter during the low state of 1980 August. The light curve shows an eclipse at phi sub m = 0.0 similar to the one observed in the customary high state. The spectral distribution of the X-ray photons does not show any soft component. The IPC flux suggests that the intensity of the hard component in the low state is about one-tenth of the intensity of the hard component during the high state, similar to the variation in the optical magnitude. The comparison of the present data with a previous SAS 3 X-ray observation of AM Her in the low state suggests that the soft component is different in similar accretion regimes. The possibility that this component originates from reprocessing of the hard flux becomes then more unlikely.

Fabbiano, G.↗

NASA NTRS1982

X-ray observations of peculiar galaxies with the Einstein Observatory

The results of X-ray observations with the Einstein Observatory of 33 galaxies are presented. Almost all of these galaxies, some of which lie in groups and in interactive pairs, display disturbed morphologies. No uniform, well-defined selection criterion can describe the sample galaxies, but almost all lie in a region of the optical color/color diagram that suggests that they are experiencing bursts of star formation. This region is compatible with the locus of Markarian galaxies. The observed sample and the X-ray data are presented, and the X-ray data are discussed and compared with the optical and radio properties of the galaxies. It is concluded that nuclear activity is not the predominant source of X-rays in late-type peculiar galaxies and that the X-ray emission is likely to originate from the Population I galactic component, in particular binary sources and possible young SNR's.

Fabbiano, G.↗

NASA NTRS1982

IUE and Einstein observations of NGC5204

The use of both the Einstein and IUE observations of NGC5204 to test some of the hypotheses put forward as a result of an X-ray survey of blue peculiar late type galaxies is discussed. In particular the hypothesis that binary X-ray sources of Pop I progenitors are responsible for most of the X-ray emission, is strengthened by the IUE short wavelength spectrum of NGC5204. This spectrum suggests a number of OB stars in agreement with the inferred from the X-ray luminosity. It also shows an ultraviolet excess in agreement with the large X-ray to blue flux ratio.

Fabbiano, G.↗

NASA NTRS1982

X-ray and UV spectra of two quasars: PKS0637-75 and PKS1004+13 (4C13.41)

Two quasars, 4C13.41 (1004+13, V approx. 15.2, z = 0.140) and PKS0637-75 (V = 15.75, z = 0.651) were observed in December 1980 with IUE. Both were detected in the short wavelength region. 4C13.41 has the lowest X-ray luminosity/optical luminosity measured in quasars. PKS0637-75 was observed quasi-simultaneously with the Einstein Observatory and a spectrum obtained with the IPC. The UV and soft X-ray spectra have been combined and are discussed together with the optical and infrared data for both objects.

Elvis, M.↗

NASA NTRS1981

Results from an extensive Einstein stellar survey

The preliminary results of the Einstein Observatory stellar X-ray survey are presented. To date, 143 soft X-ray sources have been identified with stellar counterparts, leaving no doubt that stars in general constitute a pervasive class of low-luminosity galactic X-ray sources. Stars along the entire main sequence, of all luminosity classes, pre-main sequence stars as well as very evolved stars have been detected. Early type OB stars have X-ray luminosities in the range 10 to the 31st to 10 to the 34th ergs/s; late type stars show a somewhat lower range of X-ray emission levels, from 10 to the 26th to 10 to the 31st ergs/s. Late type main-sequence stars show little dependence of X-ray emission levels upon stellar effective temperature; similarly, the observations suggest weak, if any, dependence of X-ray luminosity upon effective gravity. Instead, the data show a broad range of emission levels (about three orders of magnitude) throughout the main sequence later than F0.

Vaiana, G. S.↗