We study the inverse Compton scattering of solar photons by Galactic cosmic-ray electrons. We show that the gamma-ray emission from this process is substantial with the maximum flux in the direction ...of the Sun; the angular distribution of the emission is broad. This previously-neglected foreground should be taken into account in studies of the diffuse Galactic and extragalactic gamma-ray emission. Furthermore, observations by GLAST can be used to monitor the heliosphere and determine the electron spectrum as a function of position from distances as large as Saturn's orbit to close proximity of the Sun, thus enabling unique studies of solar modulation. This paves the way for the determination of other Galactic cosmic-ray species, primarily protons, near the solar surface which will lead to accurate predictions of gamma rays from pp-interactions in the solar atmosphere. These albedo gamma rays will be observable by GLAST, allowing the study of deep atmospheric layers, magnetic field(s), and cosmic-ray cascade development. The latter is necessary to calculate the neutrino flux from pp-interactions at higher energies (>1 TeV). Although this flux is small, it is a "guaranteed flux" in contrast to other astrophysical sources of neutrinos, and may be detectable by km^3 neutrino telescopes of the near future, such as IceCube. Since the solar core is opaque for very high-energy neutrinos, directly studying the mass distribution of the solar core may thus be possible.
Astrophys.J. 607 (2004) L99-L102 We argue that luminous infrared galaxies (LIGs) may constitute a newly
detectable population of gamma-ray sources for the next generation of ground
and space-based ...high energy telescopes. Additionally, we report for the first
time upper limits on their fluxes using data obtained with the EGRET telescope.
For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10\(^\circ\) from the Galactic plane, these ...clouds have typical distances of \(\sim\)150 pc, angular sizes of \(\sim1^\circ\), and masses of order tens of solar masses. These objects are passive sources of high-energy \(\gamma\)-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-latitude clouds are not bright enough in \(\gamma\)-rays to have been detected by EGRET, but that of order 100 of them will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict a new steady population of \(\gamma\)-ray sources at high Galactic latitudes, perhaps the most numerous after active galactic nuclei.
Previous multichannel observations of W485A (WD 1327-08) have placed it in the "instability strip," the effective temperature range 11,000 K-13,000 K. In the instability strip, most of the stars (the ...ZZ Ceti stars) are variable, but W485A has not been detected to be variable. In this paper we use high-resolution spectra of W485A, and improved hydrogen-line broadening routines in our model-atmospheres program to find the temperature of W485A; our best estimate of T eff , most consistent with the other data on the star, is 14,600 K, outside the instability strip.
Analyzing data from GLAST's Large Area Telescope (LAT) will require
sophisticated techniques. The PSF and effective area are functions of both
photon energy and the position in the field-of-view. ...During most of the mission
the observatory will survey the sky continuously and thus the LAT will detect
each count from a source at a different detector orientation; each count
requires its own response function! The likelihood as a function of celestial
position and photon energy will be the foundation of the standard analysis
techniques. However the 20 MeV-300 GeV emission at the time of the ~100 keV
burst emission (timescale of ~10 s) can be isolated and analyzed because
essentially no non-burst counts are expected within a PSF radius of the burst
location during the burst. Both binned and unbinned (in energy) spectral
fitting will be possible. Longer timescale afterglow emission will require the
likelihood analysis that will be used for persistent sources.
Using the IRAS Infrared Sky Survey Atlas, we have made 60 x 60 deg mosaics of
the far-infrared emission in the Milky Way. By applying a median normalizing
spatial filter, we were able to eliminate ...the strong gradient in brightness
towards the Galactic midplane. The resulting images reveal a "froth" of
superposed filaments, voids, and shells. This fine-scale structure extends all
the way down to the Galactic midplane. Moreover, it scales in intensity with
the smoothly varying background, independent of latitude, thus indicating that
the fine-scale residual emission is co-extensive with the smooth background. We
conclude that the fine-scale structure is not merely of local origin, but
consists of both nearby and more distant features in the disk. Although we had
expected to find morphological evidence for supernova-driven "worms" or
"chimneys" rooted in the Galactic plane, our processing shows the FIR
fine-scale structure to be more complex (e.g. less coherent and less rooted) as
viewed in projection. Analysis of the spatial statistics shows that the FIR
fine-scale structure is self-similar with a spatial power-law exponent of -3
and a fractal dimension of 2.5 --- similar behavior to that found in isolated
cirrus and molecular clouds. On scales larger than 1.5 deg, the power-law
exponent flattens to -2.5, perhaps indicating a change in the characteristic
structure. This could be due to different dynamical inputs organizing the small
and large-scale structures (e.g. turbulence and diffusion on small scales vs.
macroscopic winds and shock fronts on larger scales).
We argue that luminous infrared galaxies (LIGs) may constitute a newly detectable population of gamma-ray sources for the next generation of ground and space-based high energy telescopes. ...Additionally, we report for the first time upper limits on their fluxes using data obtained with the EGRET telescope.
Analyzing data from GLAST's Large Area Telescope (LAT) will require sophisticated techniques. The PSF and effective area are functions of both photon energy and the position in the field-of-view. ...During most of the mission the observatory will survey the sky continuously and thus the LAT will detect each count from a source at a different detector orientation; each count requires its own response function! The likelihood as a function of celestial position and photon energy will be the foundation of the standard analysis techniques. However the 20 MeV-300 GeV emission at the time of the ~100 keV burst emission (timescale of ~10 s) can be isolated and analyzed because essentially no non-burst counts are expected within a PSF radius of the burst location during the burst. Both binned and unbinned (in energy) spectral fitting will be possible. Longer timescale afterglow emission will require the likelihood analysis that will be used for persistent sources.
Using the IRAS Infrared Sky Survey Atlas, we have made 60 x 60 deg mosaics of the far-infrared emission in the Milky Way. By applying a median normalizing spatial filter, we were able to eliminate ...the strong gradient in brightness towards the Galactic midplane. The resulting images reveal a "froth" of superposed filaments, voids, and shells. This fine-scale structure extends all the way down to the Galactic midplane. Moreover, it scales in intensity with the smoothly varying background, independent of latitude, thus indicating that the fine-scale residual emission is co-extensive with the smooth background. We conclude that the fine-scale structure is not merely of local origin, but consists of both nearby and more distant features in the disk. Although we had expected to find morphological evidence for supernova-driven "worms" or "chimneys" rooted in the Galactic plane, our processing shows the FIR fine-scale structure to be more complex (e.g. less coherent and less rooted) as viewed in projection. Analysis of the spatial statistics shows that the FIR fine-scale structure is self-similar with a spatial power-law exponent of -3 and a fractal dimension of 2.5 --- similar behavior to that found in isolated cirrus and molecular clouds. On scales larger than 1.5 deg, the power-law exponent flattens to -2.5, perhaps indicating a change in the characteristic structure. This could be due to different dynamical inputs organizing the small and large-scale structures (e.g. turbulence and diffusion on small scales vs. macroscopic winds and shock fronts on larger scales).
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