Solar abundance determination from ultraviolet emission lines.
Relative solar abundance for O, Si and Fe determined from intensities of far UV emission lines of solar corona
SPECTRAL LINE↗
SEARCH · Engineering Papers
Results for “spectral emissivity”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Laboratory studies of 3.3 micron emission from naphthalene induced by 193 and 248 nanometer excitation
Laboratory studies of infrared emission from gas-phase naphthalene in the 3.3 micrometer region following ultraviolet laser excitation are used to interpret the unidentified infrared bands observed in many astronomical objects. A time-resolved Fourier transform infrared emission technique acquires the time and spectrally resolved data. Two excitation wavelengths are employed: 193 nm and 248 nm. The infrared emission features are strongly dependent on the initial excitation energy. Wavelength-resolved spectra recorded 6.8 microseconds after the laser pulse show a 45/cm redshift from the gas-phase absorption spectra for 193 nm excitation and 25/cm for 248 nm excitation. We hypothesize that a series of sequence bands originating from the highly vibrationally excited ensemble of molecules is responsible for the observed shift. As collisional and radiative deactivation removes energy from the highly vibrationally excited molecules, the maximum in the emission profile gradually approaches the customary absorption maximum. This indicates that the amount of redshift is strongly dependent on the amount of internal vibrational energy in the molecule at the time of the vibrational transition.
Williams, Richard M.↗
PCA/HEXTE Observations of M82 and NGC253
The nearby starburst galaxies M82 & NGC 253 were observed by the RXTE satellite during the period February - November 1997. Data reduction and analysis began in summer 1998, and continued through March 1999. The spectral analysis indicates that the main emission in these galaxies is from hot gas. We find a considerable degree of variability in the emission from M82, possibly due to M81 (a known AGN) in the FOV. The main spectral parameters were determined for both sources. The results of the analysis were reported in the March 1999 meeting of the AAS. Summary of the data analysis, theoretical modeling, and interpretation will be presented in a paper which is currently being prepared for publication in the Astrophysical Journal.
Rephaeli, Yoel↗
Beamed and Unbeamed X-Ray Emission in FR1 Radio Galaxies
The research exploited ROSAT's sensitivity, together with its spatial and spectral resolution, to separate X-ray emission components in the sources. Prior to ROSAT, the dominant X-ray emission mechanism in radio galaxies as a class was unclear, with correlations between the X-ray and radio emission used on one hand to argue for a nuclear origin for the X-rays, and on the other hand for a thermal origin. Our observations (normally between 10 and 25 ks in length) routinely detected the target sources, and demonstrated that both resolved (thermal) and unresolved X-ray emission are typically present. Highlights of our work included two of the first detections of high-power radio galaxies at high redshift, 3C 280 and 3C 220.1. When combined with the work of two other groups, we find that of the 38 radio galaxies at z > 0.6 in the 3CRR sample, 12 were observed in ROSAT pointed observations and 9 were detected with the four most significant detections exhibiting source extent, including 3C 280 and 3C 220.1. Moreover, we discovered extended emission around five 3CRR quasars at redshift greater than about 0.4, one of which is at z > 0.6. Unification predicts that the X-ray environments of powerful radio galaxies and quasars should be similar, and our results show that powerful radio sources are finding some of the highest-redshift X-ray clusters known to date, pointing to deep gravitational potential wells early in the Universe.
Worrall, Diana M.↗
Anomaly observed in spectral data recorded on a hypersensitized film.
Elliptical patterns on emission lines of argon plasma jets attributed to antihalation backing during hypersensitization of film
ARGON PLASMA↗
Planck 2018 results - IV. Diffuse component separation
We present full-sky maps of the cosmic microwave background (CMB) and polarized synchrotron and thermal dust emission, derived from the third set of Planck frequency maps. These products have significantly lower contamination from instrumental systematic effects than previous versions. The methodologies used to derive these maps follow closely those described in earlier papers, adopting four methods (Commander, NILC, SEVEM, and SMICA) to extract the CMB component, as well as three methods (Commander, GNILC, and SMICA) to extract astrophysical components. Our revised CMB temperature maps agree with corresponding products in the Planck 2015 delivery, whereas the polarization maps exhibit significantly lower large-scale power, reflecting the improved data processing described in companion papers; however, the noise properties of the resulting data products are complicated, and the best available end-to-end simulations exhibit relative biases with respect to the data at the few percent level. Using these maps, we are for the first time able to fit the spectral index of thermal dust independently over 3° regions. We derive a conservative estimate of the mean spectral index of polarized thermal dust emission of β d = 1.55 ± 0.05, where the uncertainty marginalizes both over all known systematic uncertainties and different estimation techniques. For polarized synchrotron emission, we find a mean spectral index of β s = -3.1 ± 0.1, consistent with previously reported measurements. We note that the current data processing does not allow for construction of unbiased single-bolometer maps, and this limits our ability to extract CO emission and correlated components. The foreground results for intensity derived in this paper therefore do not supersede corresponding Planck 2015 products. For polarization the new results supersede the corresponding 2015 products in all respects.
79 ASTRONOMY AND ASTROPHYSICS↗
Ruby laser induced emission from NO2
Two different types of emission from excited NO2 were observed using pulsed ruby laser light at 6943 A. The first type of fluorescence was seen in the near IR and results from the single photon excitation of NO2 from the ground 2-A1 state. By observing the emission as a function of time an unexpected behavior was observed in the near IR and could be explained by a consecutive deactivation mechanism, wherein a secondary species is preferentially detected. A second type of emission recently observed in the blue spectral region is weaker and is due to a multiphoton process. The intensity of the blue emission is a function of the cube of the laser intensity at low pressures and approaches the square at high pressures. This variation is attributed to simultaneous deactivation of the excited NO2 intermediate by collision (square) and by anti-Stokes Raman scattering off of the excited NO2 (cube).
Hakala, D. F.↗
Atom femtosecond optical trap based on spectrally filtered laser radiation
We have examined the use of alkali metal (rubidium) vapour for spectral filtering of broadband pulsed laser light that is used to produce a femtosecond pulsed optical dipole trap. It has been shown that, even at large detuning of the centre emission frequency from the frequency of atomic transitions, spectral components present in the wings of the laser emission line are capable of heating localised atoms, thus reducing their lifetime in the atomic trap. Using atomic vapour for filtering the laser emission spectrum, we have suppressed its spectral components resulting in heating. This has made it possible to increase the lifetime of atoms in the pulsed optical dipole trap to a value comparable to their lifetime in an optical trap formed by narrow-band cw laser light. (paper)
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Reversed far-infrared line emission from OH in Orion
The fundamental OH rotational transition at 2514 GHz has been observed in the Orion IRc2 region at a spectral resolution of 0.6 km/s. The emission is spatially compact and centered near IRc2. A comparison of the observed profile with spectra of other species known to exist in the region suggests that the entire blueshifted side of the OH profile has been self-absorbed, leaving only a redshifted emission component.
Betz, A. L.↗
The NuSTAR View of the Non-Thermal Emission from PSR J0437-4715
We present a hard X-ray Nuclear Spectroscopic Telescope Array (NuSTAR) observation of PSR J0437-4715, the nearest millisecond pulsar. The known pulsations at the apparent pulse period approximately 5.76 ms are observed with a significance of 3.7sigma, at energies up to 20 keV above which the NuSTAR background dominates. We measure a photon index gamma = 1.50 +/- 0.25(90 per cent confidence) for the power-law fit to the non-thermal emission. It had been shown that spectral models with two or three thermal components fit the XMM-Newton spectrum of PSR J0437-4715, depending on the slope of the power-law component, and the amount of absorption of soft X-rays. The new constraint on the high-energy emission provided by NuSTAR removes ambiguities regarding the thermal components of the emission below 3 keV. We performed a simultaneous spectral analysis of the XMM-Newton and NuSTAR data to confirm that three thermal components and a power law are required to fit the 0.3-20 keV emission of PSR J0437-4715. Adding a ROSAT-PSPC spectrum further confirmed this result and allowed us to better constrain the temperatures of the three thermal components. A phase resolved analysis of the NuSTAR data revealed no significant change in the photon index of the high-energy emission. This NuSTAR observation provides further impetus for future observations with the NICER mission (Neutron Star Interior Composition Explorer) whose sensitivity will provide much stricter constraints on the equation of state of nuclear matter by combining model fits to the pulsars phase-folded light curve with the pulsars well-defined mass and distance from radio timing observations.
stars; neutro↗
Rocket and spacecraft studies of ultraviolet emissions from astrophysical targets
Rocket and spacecraft far-UV spectral measurements of several astrophysical targets are reviewed. These include observations of Ly-alpha emissions from Arcturus, Apollo-17 far-UV spectrometry of eta UMa and five other stars, Apollo-17 observations of the lunar atmosphere and the diffuse UV background, and far-UV spectral studies of Venus, Jupiter, and Comet Kohoutek. The Arcturus observations indicated a chromosphere with neutral atomic-hydrogen and atomic-oxygen emissions as well as a very weak atomic-carbon line. The planetary studies revealed O I and C I emissions in the Venusian spectrum as well as large Ly-alpha emissions and possible molecular-hydrogen emissions in that of Jupiter. The lunar observations demonstrated that solar protons do not produce an atomic-hydrogen atmosphere on the moon.
Fastie, W. G.↗
Remote sensing of the surface emissivity at 9 microns over the globe
The infrared spectral measurements made by the Nimbus 4 infrared interferometer spectrometer (Iris) for a period of about 10 months are used to study the surface emissivity properties over the globe. It is found that the surface emissivity at 9 microns, as measured by Iris with a circular field of view of about 100-km diameter, is significantly less than unity over arid and semiarid areas. The spectral features in the 8-12-micron window observed over these lands reveal emissivity characteristics essentially due to quartz (SiO2). It is found that these emissivity features are significantly weakened by the presence of clay, clay horizons, or pedogenic horizons in the soil. Low emissivity is observed over sandy or sandy loam areas (psamments) with no clay or pedogenic horizons.
Prabhakara, C.↗
Fermi Constraints on the Ejecta Speed and Prompt Emission Region of the Distant GRB 220101A
At redshift z = 4.618, GRB 220101A is the most distant gamma-ray burst (GRB) detected by Fermi/LAT to date. It is also a very energetic event, with an equivalent isotropic energy of 3.6 × 10 54 erg. We jointly analyzed the Fermi/GBM and LAT observations of GRB 220101A with two independent approaches and found a significant spectral break at sub-100 MeV energies during the prompt emission. The fast variability of the emission suggests that this spectral attenuation is caused by internal opacity to pair creation. Regardless of the nature of the emission processes assumed in the spectral analysis, we infer a moderate value for the jet Lorentz factor, Γ ~ 110, and find that all of the high-energy emission was produced above and near the photosphere, at a distance of ~10 14 cm from the central engine. We compare these results with the four other LAT-detected GRBs with similar properties.
79 ASTRONOMY AND ASTROPHYSICS↗
Temporal Profiles and Spectral Lags of XRF 060218
The spectral and temporal properties of the nonthermal emission of the nearby XRF 060218 in the 0.3-150 keV band are studied. We show that both the spectral energy distribution and the light-curve properties suggest the same origin of the nonthermal emission detected by Swift BAT and XRT. This event has the longest pulse duration and spectral lag observed to date among the known GRBs. The pulse structure and its energy dependence are analogous to typical GRBs,. By extrapolating the observed spectral lag to the Compton Gamma Ray Observatory (CGRO) BATSE bands we find that the hypothesis that this event complies with the same luminosity-lag relation with bright GRBs cannot be ruled out at 2 sigma significance level. These intriguing facts, along with its compliance with the Amati relation, indicate that XRF 060218 shares the similar radiation physics as typical GRBs.
Liang, En-Wei↗
On the Discovery of CO Nighttime Emissions on Titan by Cassini/VIMS: Derived Stratospheric Abundances and Geological Implications
We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147] in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 microns. For CH3D, the prominent Q branch of the nu(2) fundamental band of CH3D near 4.55 microns is apparent. CO2 emissions from the strong nu(3) vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32 +/- 15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is similar to 2.9 +/- 1.5 x 10(exp 14) kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (similar to 0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6 +/- 3 x 10(exp 5) kg yr(exp -1). Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8 +/- 0.9 x 10(exp -4), based on an average methane surface emission rate over the past 0.5 Gyr of 1.3 x 10(exp -13) gm cm(exp -2) s(exp -1) as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi: 10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is approximately 0.02 km(exp 3) yr (exp -1), a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant geological processes reshaping the surface of Titan.
carbon compounds↗
Heating analysis for the Pioneer Venus multiprobe mission
The fully coupled, radiating flow field around the entry probes is determined from a detailed calculation which includes equilibrium chemistry, nongray radiative transport, ablation product injection, and a laminar or turbulent boundary layer. Results show that the radiative flux toward the body is attenuated in the boundary layer at downstream regions of the body as well as at the stagnation point and that, even when radiation absorption by ablation products is accounted for, the radiative heating rates along the downstream regions of the body can, under certain conditions, exceed the stagnation point values. It is also shown that, for Venusian entry, the spectral distribution of radiative flux and the magnitude of radiation absorption by ablation products depend strongly on entry velocity, and that the state of the boundary layer can significantly influence the amount of ablation product absorption or emission that occurs in various spectral regions.
Sutton, K.↗
A Deep X-Ray View of the Synchrotron-Dominated Supernova Remnant G330.2+1.0
We present moderately deep (125 ks) XMM-Newton observations of supernova remnant G330.2+1.0. This remnant is one of only a few known that fall into the "synchrotron-dominated" category, with the emission almost entirely dominated by a nonthermal continuum. Previous X-ray observations could only characterize the spectra of a few regions. Here, we examine the spectra from 14 regions surrounding the entire rim, finding that the spectral properties of the nonthermal emission do not vary significantly in any systematic way from one part of the forward shock to another, unlike several other remnants of this class. We confirm earlier findings that the power-law index, Γ, ranges from about 2.1-2.5, while the absorbing column density is generally between (2.0-2.6) × 10(exp 22) cm(exp -2). Fits with the srcut model find values of the roll-off frequency in the range of 10(exp 17.1)-10(exp 17.5) Hz, implying energies of accelerated electrons of approximately 100 TeV. These values imply a high shock velocity of approximately 4600 km s(exp -1), favoring a young age of the remnant. Diffuse emission from the interior is nonthermal in origin as well, and fits to these regions yield similar values to those along the rim, also implying a young age. Thermal emission is present in the east, and the spectrum is consistent with approximately 650 km s(exp -1) shock wave encountering interstellar or circumstellar material with a density of approximately 1 cm(exp -3).
Williams, Brian J.↗