Photon Spectral Index Research Articles

Implications of solar flare hard X-ray “knee” spectra observed by RHESSI

We analyse the RHESSI photon spectra of four flares that exhibit significant deviations from power laws – i.e. changes in the “local” Hard X-ray spectral index. These spectra are characterised by two regions of constant power law index connected by a region of changing spectral index – the “knee”. We develop theoretical and numerical methods of describing such knees in terms of variable photon spectral indices and we study the results of their inversions for source mean thin target and collisional thick target injection electron spectra. We show that a particularly sharp knee can produce unphysical negative values in the electron spectra, and we derive inequalities that can be used to test for this without the need for an inversion to be performed. Such unphysical features would indicate that source model assumptions were being violated, particularly strongly for the collisional thick target model which assumes a specific form for electron energy loss. For all four flares considered here we find that the knees do not correspond to unphysical electron spectra. In the three flares that have downward knees we conclude that the knee can be explained in terms of transport effects through a region of non-uniform ionisation. In the other flare, which has an upward knee, we conclude that it is most likely a feature of the accelerated spectrum.

B eppo SAX Average Spectra of Seyfert Galaxies

We have studied the average 3-200 keV spectra of Seyfert galaxies of type 1 and 2, using data obtained with BeppoSAX. The average Seyfert 1 spectrum is well fitted by a power-law continuum with photon spectral index Γ ~ 1.9, a Compton reflection component R ~ 0.6-1 (depending on the inclination angle between the line of sight and the reflecting material), and a high-energy cutoff at around 200 keV; there is also an iron line at 6.4 keV characterized by an equivalent width of 120 eV. Seyfert 2 galaxies, on the other hand, show stronger neutral absorption [NH = × 1022 atoms cm-2], as expected, but are also characterized by an X-ray power law that is substantially harder (Γ ~ 1.75) and with a cutoff at lower energies (Ec ~ 130 keV); the iron line parameters are instead substantially similar to those measured in type 1 objects. There are only two possible solutions to this problem: to assume more reflection in Seyfert 2 galaxies than observed in Seyfert 1 galaxies or more complex absorption than estimated in the first instance. The first possibility is ruled out by the Seyfert 2 to Seyfert 1 ratio, while the second provides an average Seyfert 2 intrinsic spectrum very similar to that of the Seyfert 1. The extra absorber is likely an artifact due to summing spectra with different amounts of absorption, although we cannot exclude its presence in at least some individual sources. Our result argues strongly for a very similar central engine in both types of galaxies, as expected under the unified theory.

Multiple Components of the Luminous Compact X-Ray Source at the Edge of Holmberg II Observed by [ITAL]ASCA[/ITAL] and [ITAL]ROSAT[/ITAL

We report the results of the analysis of ASCA/ROSAT observations of the compact luminous X-ray source found at the edge of the nearby star-forming dwarf galaxy Holmberg II (UGC 4305).Our ASCA spectrum revealed that the X-ray emission extends to the hard band and can be best described by a power-law with a photon spectral index of 1.9. The ASCA spectrum does not fit with a multi-color disk blackbody. The joint ASCA-ROSAT spectrum suggests two components to the spectrum: the hard power-law component and a warm thermal plasma kT~0.3[keV]. An additional absorption over that of our galaxy is required. The wobble correction of the ROSAT HRI image has clearly unveiled the existence of an extended component which amounts to 27+/-5% of the total X-ray emission. These observations indicate that there are more than one component in the X-ray emission. The properties of the point-like component is indicative of an accretion onto an intermediate mass blackhole, unless a beaming is taking place. We argue that the extended component does not come from electron scattering and/or reflection by scattered optically-thick clouds of the central radiation. Possible explanations of this X-ray source include multiple supernova remnants feeding an intermediate-mass blackhole. (abridged)

Synchrotron Radiation as the Source of Gamma‐Ray Burst Spectra

We investigate synchrotron emission models as the source of gamma-ray burst spectra. We show that including the possibility for synchrotron self-absorption, a ``smooth cutoff'' to the electron energy distribution, and an anisotropic distribution for the electron pitch angles produces a whole range of low energy spectral behavior. In addition, we show that the procedure of spectral fitting to GRB data over a finite bandwidth can introduce a spurious correlation between spectral parameters - in particular, the value of the peak of the nu F_nu spectrum, E_p, and the low energy photon spectral index alpha (the lower E_p is, the lower (softer) the fitted value of alpha will be). From this correlation and knowledge of the E_p distribution, we show how to derive the expected distribution of alpha. We show that optically thin synchrotron models with an isotropic electron pitch angle distribution can explain the distribution of alpha below alpha=-2/3. This agreement is achieved if we relax the unrealistic assumption of the presence of a sharp low energy cutoff in the spectrum of accelerated electrons, and allow for a more gradual break. We show that this low energy portion of the electron spectrum can be at most flat. We also show that optically thin synchrotron models with an anisotropic electron pitch angle distribution can explain all bursts with -2/3 < alpha <= 0$. The very few bursts with low energy spectral indices that fall above alpha=0 may be due the presence of a the synchrotron self-absorption frequency entering the lower end of the BATSE window. Our results also predict a particular relationship between alpha and E_p during the temporal evolution of a GRB. We give examples of spectral evolution in GRBs and discuss how the behavior are consistent with the above models.

A High‐Sensitivity Measurement of the MeV Gamma‐Ray Spectrum of Cygnus X‐1

The Compton Gamma Ray Observatory (CGRO) has observed the Cygnus region on several occasions since its launch in 1991. The data collected by the COMPTEL experiment on CGRO represent the most sensitive observations to date of Cygnus X-1 in the 0.75-30 MeV range. A spectrum accumulated by COMPTEL over 10 weeks of observation time shows significant evidence for emission extending out to several MeV. We have combined these data with contemporaneous data from both BATSE and OSSE to produce a broadband γ-ray spectrum, corresponding to the low X-ray state of Cygnus X-1, extending from 50 keV up to ~5 MeV. Although there is no evidence for any broad-line-like emissions in the MeV region, these data further confirm the presence of a hard tail at energies above several hundred keV. In particular, the spectrum at MeV energies can be described as a power law with a photon spectral index of α = -3.2, with no evidence for a cutoff at high energies. For the 200 keV-5 MeV spectrum, we provide a quantitative description of the underlying electron spectrum, in the context of a hybrid thermal/nonthermal model for the emission. The electron spectrum can be described by a thermal Maxwellian with a temperature of kTe = 86 keV and a nonthermal power-law component with a spectral index of pe = 4.5. The spectral data presented here should provide a useful basis for further theoretical modeling.

Observation of an Extra Emission around 2 MeV in the Spectrum of an Intense Gamma‐Ray Burst

We present a time-averaged spectral analysis (0.1-100 MeV) of two intense γ-ray bursts detected by the PHEBUS experiment. The νfν spectra of these two events are observed to peak between 1 and 2 MeV. For the least intense of the two bursts, a single maximum in νfν is seen. For the other, there is a suggestion of two peaks, with similar strengths, at ~1 and ~2 MeV. The most commonly used photon models, with four or five parameters, provide inadequate fits to the latter spectrum. We have tested two seven-parameter models that satisfactorily fit the observations by the two brightest detectors of the stronger event. Both of them are built from and compared with the standard four-parameter γ-ray burst (GRB) function. The first model assumes an additional emission described by a Gaussian expression. The second one supposes a further spectral break at higher energy. For the two models, we find an extra emission around 2 MeV relative to the standard GRB model. In addition, the second seven-parameter model supports a sudden change in the photon spectral index from about -2 to -3.6 over a restricted energy range near 2.4 MeV. The probability of rejecting, as due to chance, these two models relative to the standard four-parameter expression does not exceed 6.8 × 10-8. Although its origin is unclear, the 2 MeV emission excess may provide important constraints on the physical conditions and radiation mechanisms at the emission site of γ-ray bursts.

SAX J1810.8−2609: A New Hard X‐Ray Bursting Transient

The transient X-ray source SAX J1810.8-2609 was discovered on 1998, March 10 with the Wide Field Cameras on board the BeppoSAX satellite, while observing the Galactic Bulge in the 2-28 keV energy range. On March 11, a strong type-I X-ray burst was detected with evidence of photospheric radius expansion. A follow-up target of opportunity observation with the Narrow-Field Instruments (NFI) was performed on March 11 and 12, for a total elapsed time of 8.51 x 10^{4} s. The wide band spectral data (0.1-200 keV) obtained with the NFI show a remarkable hard X-ray spectrum detected up to ~200 keV, which can be described by a power law with photon spectral index Gamma=1.96\pm0.04, plus a soft component which is compatible with blackbody radiation of temperature kT~0.5 keV. The detection of the type-I X-ray burst is a strong indication that the compact object is a neutron star in a low mass X-ray binary system. Assuming standard burst parameters and attributing the photospheric radius expansion to near Eddington luminosity, we estimate a distance of ~5 kpc. The inferred 2-10 keV X-ray luminosity is ~ 9 x 10^{35} erg/s at the time of the discovery.

Hard x-ray and Microwave Flux Spectra of the 2 November 1991 Solar Flare

We analysed the hard X-ray and microwave flux spectra of the solar flare (BATSE No. 1791) on 2 November 1991, which started at 16:11:03 UT and ended at 16:56:10 UT. This flare is particularly interesting because of its deep cyclic intensity modulation. Data are available simultaneously from the 16-channel BATSE/LAD hard X-ray and 45-frequency OVRO microwave database. We quantitatively compare the time variations in profiles of the hard X-ray spectral photon index, the 50 keV X-ray flux, and microwave spectral indices (at both high and low frequency ends). As expected, the X-ray photon spectral index decreases as the hard X-ray flux increases. This pattern appears in all the sub-peaks. This is consistent with previous observations that hard X-ray emission hardens at the emission peak. However, the behaviour of the high-frequency microwave index is unexpected. We observe an anti-correlation between the high-frequency microwave index and the hard X-ray photon index during the course of the flare. Finally, we study the arrival time of microwave flux peaks as a function of frequency and find that the microwave peak at a higher frequency comes earlier than that at a lower frequency. A maximum delay of 72 s is found among the main peaks at different frequencies. Shorter delays are found for the other five sub-peaks.

Broad-band X-ray/γ-ray spectra and binary parameters of GX 339–4 and their astrophysical implications

We present X-ray/γ-ray spectra of the binary GX 339–4 observed in the hard state simultaneously by Ginga and CGRO OSSE during an outburst in 1991 September. The Ginga X-ray spectra are well represented by a power law with a photon spectral index of Γ ≃ 1.75 and a Compton reflection component with a fluorescent Fe Kα line corresponding to a solid angle of an optically thick, ionized medium of ∼ 0.4 × 2 π. The OSSE data (≥ 50 keV) require a sharp high-energy cut-off in the power-law spectrum. The broad-band spectra are very well modelled by repeated Compton scattering in a thermal plasma with an optical depth of τ ∼ 1 and kT ≃ 50 keV. We also study the distance to the system and find it to be ≳ 3 kpc, ruling out earlier determinations of ∼ 1 kpc. Using this limit, the observed reddening and the orbital period, we find the allowed range of the mass of the primary is consistent with it being a black hole. We find the data are inconsistent with models of either homogenous or patchy coronae above the surface of an accretion disc. Rather, they are consistent with the presence of an inner hot disc with the viscosity parameter of α ∼ 1 accreting at a rate close to the maximum set by advection. The hot disc is surrounded by a cold outer disc, which gives rise to the reflection component and a soft X-ray excess, also present in the data. The seed photons for Comptonization are unlikely to be due to thermal synchrotron radiation. Rather, they are supplied by the outer cold disc and/or cold clouds within the hot disc. e± pair production is negligible if electrons are thermal. The hot disc model, for which scaled parameters are independent of the black hole mass, is supported by the similarity of the spectrum of GX 339–4 to those of other black hole binaries and Seyfert 1s. On the other hand, their spectra in the soft γ-ray regime are significantly harder than those of weakly magnetized neutron stars. Based on this difference, we propose that the presence of broad-band spectra corresponding to thermal Comptonization with kT ≳ 50 keV represents a black hole signature.

Observations of a Correlated Gamma-Ray and Optical Flare for BL Lacertae

BL Lacertae was detected by the EGRET instrument on the Compton Gamma Ray Observatory at the 10.2 σ level with an average flux of (171 ± 42) × 10−8 photons cm-2 s-1, at energies greater than 100 MeV, during the optical outburst of 1997 July. This flux is more than 4 times the previously highest level. Within the July 15-22 observation there was a dramatic factor of 2.5 increase in the gamma-ray flux on July 18.75-19.08, apparently preceding, by several hours, a brief optical flare. The gamma-ray flux decreased to its previous level within 8 hr, and the optical flux decreased to its prior level in less than 2 hr. The gamma-ray photon spectral index of 1.68±0.12 indicates that the spectrum during the 7 day observation was harder than the previous detection.

Multiwavelength Observations of 3C 273 in 1993–1995

We present the results of the multi-wavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993 this quasar showed an increase of its flux for energies >= 100 MeV from about 2.1 x 10(exp -7) photons/sq cm.s to approximately 5.6 x 10(exp -7) photons/sq cm.s during a radio outburst at 14.5, 22 and 37 GHz. However, no one-to-one correlation of the gamma-ray radiation with any frequency could be found. The photon spectral index of the high energy spectrum changed from GAMMA(sub gamma) = (3.20 +/- 0.54) to GAMMA(sub gamma) = (2.20 +/- 0.22) in the sense that the spectrum flattened when the gamma-ray flux increased. Fits of the three most prominent models (synchrotron self-Comptonization, external inverse Comptonization and the proton initiated cascade model) for the explanation of the high gamma-ray emission of active galactic nuclei were performed to the multi-wavelength spectrum of 3C 273 . All three models are able to represent the basic features of the multi-wavelength spectrum. Although there are some differences the data are still not decisive enough to discriminate between the models.

ASCA observations of deep ROSAT fields -- I. The nature of the X-ray source populations

We present ASCA GIS observations (total exposure 100-200 ksec) of three fields which form part of our deep ROSAT survey. We detect 26 sources down to a limiting flux (2-10 keV) of 5x10^{-14} erg cm-2 s-1. Sources down to this flux level contribute 30 per cent of the 2-10 keV X-ray background. The number-count distribution, logN-logS, is a factor of three above the ROSAT counts, assuming a photon spectral index of 2 for the ROSAT sources. This suggests the presence at hard energies of a population other than the broad-line AGN which contribute to the ROSAT counts. This is supported by spectroscopic observations that show a large fraction of sources that are not obvious broad-line AGN. The average 1-10 keV spectral index of these sources is flat (0.92+-0.16), significantly different than that of the broad-line AGN (1.78+-0.16). Although some of the Narrow Emission Line Galaxies which are detected with ROSAT are also detected here, the nature of the flat spectrum sources remains as yet unclear.

Advection‐dominated Accretion Model of the Black Hole V404 Cygni in Quiescence

We have analyzed archival ASCA data on the soft X-ray transient source V404 Cyg in quiescence. We find that in the energy range 0.7-8.5 keV the spectrum is a hard power law with a photon spectral index between 1.8 and 2.6 (90% confidence limits). We present a model of V404 Cyg in which the accretion flow has two components: (1) an outer thin disk with a small annular extent and (2) a large interior region where the flow is advection dominated. Nearly all the radiation in the infrared, optical, UV, and X-ray bands is from the advection-dominated zone; the thin disk radiates primarily in the infrared where it contributes about 10% of the observed flux. The spectrum we calculate with this model is in excellent agreement with the ASCA X-ray data presented here, as well as with previous optical data. Moreover, the fit is very insensitive to the choice of parameters such as black hole mass, orbital inclination, viscosity coefficient α, and magnetic field strength. We consider the success of the model to be strong support for the advection-dominated accretion paradigm, and further evidence of the black hole nature of V404 Cyg. We discuss strategies whereby systems with advection-dominated accretion could be used to prove the reality of event horizons in black holes.

Time Variability Detected in the Gamma-Ray Emission of 3C 273 by OSSE

We report results of a 3 week observation of the quasar 3C 273 with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory (CGRO). During the observation between 1994 August 31 and September 20, 3C 273 exhibited variability on timescales as short as 3-4 days in the 0.05-0.15 MeV energy range. This is the shortest measured variability of 3C 273 in this energy range. The measured flux at 100 keV is 2.40 ± 0.06 (×10-2 ph cm-2 s-1 MeV-1), which is the highest recorded flux for 3C 273 by OSSE in 5 years of monitoring and nearly twice as great as the previously recorded peak flux measured in 1991 June. While the flux varied by a factor of 1.7, no significant gamma-ray spectral evolution in the OSSE band was observed throughout the viewing period. The data for the full viewing period are described better with a broken power law than a single power law, with photon spectral index Γ = 1.62 ± 0.08 below a break at 300 ± 100 keV, and with a spectral index change of ΔΓ = 0.9+ 1.6−0.6. This break energy is significantly lower than the 1 MeV break reported by Johnson et al. in 1991 June.

Extreme X-Ray Variability in the Narrow-Line QSO PHL 1092

view Abstract Citations (60) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Extreme X-Ray Variability in the Narrow-Line QSO PHL 1092 Forster, Karl ; Halpern, Jules P. Abstract A ROSAT observation of the narrow-line Fe II QSO PHL 1092 shows rapid variability that requires an efficiency of at least 0.13, exceeding the theoretical maximum for an accretion disk around a non-rotating black hole. Plausible explanations for this high efficiency incorporate anisotropic emission and/or accretion onto a rapidly rotating black hole, the latter being recently suggested by Kwan et al. as a mechanism for generating the strong Fe II lines of PHL 1092 by mechanical heating in an accretion disk. The soft X-ray luminosity of PHL 1092 had also increased by a factor of 21 over the weak Einstein detection, to more than 5 x 10^46^ ergs s^-1^. Its photon spectral index of 4.2 is among the steepest of any active galactic nucleus. These X-ray properties are characteristic of narrow-line Seyfert 1 galaxies, of which PHL 1092 is evidently a very luminous member. Narrow-line QSOs also extend the significant correlation between X-ray luminosity and X-ray spectral index which we have found among a large sample of optically selected, narrow-line Seyfert 1 galaxies observed by ROSAT, Publication: The Astrophysical Journal Pub Date: September 1996 DOI: 10.1086/177715 arXiv: arXiv:astro-ph/9603152 Bibcode: 1996ApJ...468..565F Keywords: GALAXIES: SEYFERT; GALAXIES: QUASARS: INDIVIDUAL ALPHANUMERIC: PG 1404+226; X-RAYS: GALAXIES; GALAXIES: QUASARS: INDIVIDUAL ALPHANUMERIC: PHL 1092; GALAXIES: ACTIVE; Astrophysics E-Print: LaTeX file, 13 pages including 3 tables and 3 postscript figures. To appear in The Astrophysical Journal full text sources arXiv | ADS | data products SIMBAD (13) NED (9) HEASARC (1)

A reflection-dominated X-ray spectrum discovered by ASCA in the Circinus galaxy

We report the first pointed X-ray observation, made by ASCA, of the nearby Seyfert 2 galaxy in Circinus. The spectrum consists of a very prominent (EW∼2 keV) fluorescent 6.4-keV iron line, a very flat continuum (photon spectral index less than 1) and other lines, including one at ∼7 keV that is probably due, at least in part, to iron K β fluorescent emission. The spectrum is consistent with Compton scattering and fluorescent emission from cold matter illuminated by an obscured active nucleus.

Two Classes of Gamma-Ray--emitting Active Galactic Nuclei: Erratum

view Abstract Citations (5) References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Two Classes of Gamma-Ray--emitting Active Galactic Nuclei: Erratum Dermer, Charles D. ; Gehrels, Neil Abstract In the paper "Two Classes of Gamma-Ray-emitting Active Galactic Nuclei" by Charles D. Dermer and Neil Gehrels (ApJ, 447, 103 [1995)), the following corrections and clarifications should be made. (l) In Table 3, the values of apparent transverse superluminal speeds given in the column labeled "hβ_app_ + h {DELTA}β_app_ should be multiplied by (4/3)^2^. (2) In equation (3), a brace is missing following the δ symbol. (3) In equation (6), the term -1 should be deleted in the integration over x', and the final term should be written n_ph_(η, μ; x'). (4) The values of F_-6_ in Table 4 are average flux values during the flaring episode; the correct value of τgammaγ_(E_100_ = 0.01) for 3C 279 is 7.3 x 10^-3^. (5) The correct values of M_8,min_^EGRET_ in Table 5 for 3C 273, 1633+382, and 0528 + 134 are 0.0014, 0.60, and 0.60, respectively. (6) The term s refers both to photon spectral index and the invariant 2ηη_1_(1 - μ). Publication: The Astrophysical Journal Pub Date: January 1996 DOI: 10.1086/176664 Bibcode: 1996ApJ...456..412D full text sources ADS | Related Materials (1) Original Paper: 1995ApJ...447..103D

EGRET Detection of Pulsed Gamma Radiation from PSR B1951+32

We detected a sixth high-energy gamma-ray pulsar, PSR B1951+32, pulsating in gamma rays at E ≥ 100 MeV with the same 39.5 ms periodicity as in radio, using the data obtained during 1991 May to 1994 July by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory. Although seen only as a weak source amidst the high background of galactic disk emission, the pulsation in high-energy gamma rays is clearly seen. The pulsed radiation has a photon spectral index of -1.74 ± 0.11. There is no evidence as yet for unpulsed emission from the object. The pulsar appears to have an efficiency of ~0.004 for converting its rotational energy loss into gamma rays at E ≥ 100 MeV.

Discovery of the 18.7 Second Accreting X-Ray Pulsar GRO J1948+32

view Abstract Citations (34) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Discovery of the 18.7 Second Accreting X-Ray Pulsar GRO J1948+32 Chakrabarty, Deepto ; Koh, Towsian ; Bildsten, Lars ; Prince, Thomas A. ; Finger, Mark H. ; Wilson, Robert B. ; Pendleton, Geoffrey N. ; Rubin, Bradley C. Abstract We have detected an 18.7 s accreting X-ray pulsar in the Cygnus region, using the BATSE large-area detectors on the Compton Gamma Ray Observatory. GRO J1948+32 has been localized to within 10 deg2 using a method we developed for positioning weak pulsed sources with BATSE. During the 33 day outburst, the phase-averaged 20-75 keV pulsed flux rose from 25 mCrab to 50 mCrab over 10 days and then decayed below our detection j-threshold over nearly 25 days. A photon spectral index of γ = 2.65±0.15 (assuming photon flux density dN/dE ∝ E-γ) was measured during a bright interval. The observed modulation of the neutron star's pulse frequency is suggestive of orbital variation over less than one orbit cycle. Assuming a constant spin frequency derivative over the outburst, we can place the following individual 95% confidence limits on each of the pulsar parameters: orbital period 35d < Porb < 70d; orbital radius 75 lt-sec < αx sin i < 300 lt-sec, eccentricity e < 0.25, spin frequency derivative 5 × 10-13 Hz s-1 < vdot < 2.5 × 10-11 Hz s-1, X-ray mass function 0.5 Msun < fx(M) < 5 Msun. As the stellar type of the mass-providing companion is still not known for this source, we briefly speculate on the nature of mass transfer in this system. Publication: The Astrophysical Journal Pub Date: June 1995 DOI: 10.1086/175839 Bibcode: 1995ApJ...446..826C Keywords: X-RAYS: STARS; STARS: PULSARS: INDIVIDUAL ALPHANUMERIC: GRO J1948+32; STARS: PULSARS: INDIVIDUAL ALPHANUMERIC: GRO J2014+34 full text sources ADS | data products SIMBAD (2) HEASARC (1)

Gamma-ray observations of Ophiuchus with EGRET: The diffuse emission and point sources

Observations of the Ophiuchus region made with the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) during the first 2 1/2 years of operation show the diffuse emission from the interstellar gas in Ophiuchus as well as variable emission from two point sources. The gamma-ray emission is modeled in terms of cosmic-ray interactions with atomic and molecular hydrogen in Ophiuchus and with low-energy photons along the line of sight. The model also includes the flux from the two point sources and an isotropic diffuse contribution. The cosmic-ray density is assumed to be uniform. The derived ratio of molecular hydrogen column density to integrated CO intensity is (1.1 +/- 0.2) x 10(exp 20) H-mols/sq cm (K km/s)(exp -1). At the sensitivity and resolution of the gamma-ray data, no variation of this ratio over the modeled region is discernible, nor are any regions of enhanced cosmic-ray density apparent. The model was fitted to seven narrow energy bands to obtain the energy depedence of the gamma-ray production function and the spectra of the point sources. The derived production function is in good agreement with theoretical calculations and the local cosmic-ray electron and proton spectra. The positions of the point sources were determined from maximum likelihood analysis of the gamma-ray emission observed in excess of the diffuse model. We identify one point source with the quasar PKS 1622-253, which has an average flux, E greater than 100 MeV, of (2.5 +/- 0.5) x 10(exp -7) photons/sq cm/s and photon spectral index -1.9 +/- 0.3. The other source, denoted GRO J1631-27, has not yet been identified at other wavelengths. Its average flux, E greater than 100 MeV, is (1.1 +/- 0.4) x 10(exp -7) photons/sq cm/s; however, its spectral index is poorly determined. The spectral index and intensity of the isotropic contribution to the model agree well with the extragalactic diffuse emission derived from the SAS 2 data.