Spatially Resolved Far-Ultraviolet Spectroscopy of the Nuclear Region of NGC 1068

We carry out high-resolution FUSE spectroscopy of the nuclear region of NGC 1068. The first set of spectra was obtained with a 30" square aperture that collects all emission from the narrow-line region. The data reveal a strong broad OVI component of FWHM ~3500 kms-1 and two narrow OVI 1031/1037 components of ~350 kms-1. The CIII 977 and NIII 991 emission lines in this spectrum can be fitted with a narrow component of FWHM ~1000 kms-1 and a broad one of ~2500 kms-1. Another set of seven spatially resolved spectra were made using a long slit of 1.25" X 20", at steps of ~1" along the axis of the emission-line cone. We find that (1) Major emission lines in the FUSE wavelength range consist of a broad and a narrow component; (2) There is a gradient in the velocity field for the narrow OVI component of ~200 kms-1 from ~2" southwest of the nucleus to ~4" northeast. A similar pattern is also observed with the broad OVI component, with a gradient of ~3000 kms-1. These are consistent with the HST/STIS findings and suggest a biconical structure in which the velocity field is mainly radial outflow; (3) A major portion of the CIII and NIII line flux is produced in the compact core. They are therefore not effective temperature diagnostics for the conical region; and (4) The best-fitted UV continuum suggests virtually no reddening, and the HeII 1085/1640 ratio suggests a consistently low extinction factor across the cone.Comment: To appear in the Astrophysical Journal. 37 pages with 12 figure

Far Ultraviolet Diffuse Emission from the Large Magellanic Cloud

We present the first observations of diffuse radiation in the far ultraviolet (1000 -- 1150 \AA) from the Large Magellanic Cloud based on observations made with the {\it Far Ultraviolet Spectroscopic Explorer}. The fraction of the total radiation in the field emitted as diffuse radiation is typically 5 -- 20\% with a high of 45\% near N70 where there are few exciting stars, indicating that much of the emission is not due to nearby stars. Much less light is scattered in the far ultraviolet than at longer wavelengths with the stellar radiation going into heating the interstellar dust.Comment: Accepted in ApJ Letter

Observations and modeling of H_2 fluorescence with partial frequency redistribution in giant planet atmospheres

Partial frequency redistribution (PRD), describing the formation of the line profile, has negligible observational effects for optical depths smaller than ~10^3, at the resolving power of most current instruments. However, when the spectral resolution is sufficiently high, PRD modeling becomes essential in interpreting the line shapes and determining the total line fluxes. We demonstrate the effects of PRD on the H_2 line profiles observed at high spectral resolution by the Far-Ultraviolet Spectroscopic Explorer (FUSE) in the atmospheres of Jupiter and Saturn. In these spectra, the asymmetric shapes of the lines in the Lyman (v"- 6) progression pumped by the solar Ly-beta are explained by coherent scattering of the photons in the line wings. We introduce a simple computational approximation to mitigate the numerical difficulties of radiative transfer with PRD, and show that it reproduces the exact radiative transfer solution to better than 10%. The lines predicted by our radiative transfer model with PRD, including the H_2 density and temperature distribution as a function of height in the atmosphere, are in agreement with the line profiles observed by FUSE. We discuss the observational consequences of PRD, and show that this computational method also allows us to include PRD in modeling the continuum pumped H_2 fluorescence, treating about 4000 lines simultaneously.Comment: 17 pages, accepted for publication in Ap

A New Analysis of the O VI Emitting Nebula around KPD 0005+5106

We present observations of O VI 1032 emission around the helium white dwarf KPD 0005+5106 obtained with the Far Ultraviolet Spectroscopic Explorer. Previously published data, reprocessed with an updated version of the calibration pipeline, are included along with new observations. The recent upward revision of the white dwarf's effective temperature to 200,000 K has motivated us to re-analyze all the data. We compare observations with photoionization models and find that the density of the O VI nebula is about 10 cm^-3, and that the stellar flux must be attenuated by about 90% by the time it impinges on the inner face of the nebula. We infer that this attenuation is due to circumstellar material ejected by KPD 0005+5106 earlier in its evolution.Comment: 21 pages, including 3 figures and 2 tables. Accepted for publication in the Astrophysical Journal. Minor change: a few uncited references remove

Model for Cameron band emission in comets: A case for EPOXI mission target comet 103P/Hartley 2

The CO2 production rate has been derived in comets using the Cameron band (a3Pi - X1Sigma) emission of CO molecule assuming that photodissociative excitation of CO2 is the main production mechanism of CO in a3Pi metastable state. We have devoloped a model for the production and loss of CO(a3Pi) which has been applied to comet 103P/Hartley 2: the target of EPOXI mission. Our model calculations show that photoelectron impact excitation of CO and dissociative excitation of CO2 can together contribute about 60-90% to the Cameron band emission. The modeled brightness of (0-0) Cameron band emission on comet Hartley 2 is consistent with Hubble Space Telescope observations for 3-5% CO2 (depending on model input solar flux) and 0.5% CO relative to water, where photoelectron impact contribution is about 50-75%. We suggest that estimation of CO2 abundances on comets using Cameron band emission may be reconsidered. We predict the height integrated column brightness of Cameron band of ~1300 R during EPOXI mission encounter period.Comment: 3 figure

CalFUSE v3: A Data-Reduction Pipeline for the Far Ultraviolet Spectroscopic Explorer

Since its launch in 1999, the Far Ultraviolet Spectroscopic Explorer (FUSE) has made over 4600 observations of some 2500 individual targets. The data are reduced by the Principal Investigator team at the Johns Hopkins University and archived at the Multimission Archive at Space Telescope (MAST). The data-reduction software package, called CalFUSE, has evolved considerably over the lifetime of the mission. The entire FUSE data set has recently been reprocessed with CalFUSE v3.2, the latest version of this software. This paper describes CalFUSE v3.2, the instrument calibrations upon which it is based, and the format of the resulting calibrated data files.Comment: To appear in PASP; 29 pages, 13 figures, uses aastex, emulateap

FUSE spectroscopy of sdOB primary of the post common-envelope binary LB 3459 (AA Dor)

LB 3459 (AA Dor) is an eclipsing, close, post common-envelope binary consisting of an sdOB primary star and an unseen secondary with an extraordinarly low mass - formally a brown dwarf. A recent NLTE spectral analysis shows a discrepancy with the surface gravity, which is derived from analyses of radial-velocity and lightcurves. We aim at precisely determing of the photospheric parameters of the primary, especially of the surface gravity, and searching for weak metal lines in the far UV. We performed a detailed spectral analysis of the far-UV spectrum of LB 3459 obtained with FUSE by means of state-of-the-art NLTE model-atmosphere techniques. A strong contamination of the far-UV spectrum of LB 3459 by interstellar line absorption hampers a precise determination of the photospheric properties of its primary star. Its effective temperature (42 kK) was confirmed by the evaluation of new ionization equilibria. For the first time, phosphorus and sulfur have been identified in the spectrum of LB 3459. Their photospheric abundances are solar and 0.01 times solar, respectively. From the C III 1174-1177A multiplet, we can measure the rotational velocity of 35 +/- 5 km/sec of the primary of LB 3459 and confirm that the rotation is bound. From a re-analysis of optical and UV spectra, we determine a higher log g = 5.3 (cgs) that reduces the discrepancy in mass determination in comparison to analyses of radial-velocity and lightcurves. However, the problem is not completely solved.Comment: 10 pages, 15 figure

Highly Ionized Collimated Outflow from HE 0238 - 1904

We present a detailed analysis of a highly ionized, multiphased and collimated outflowing gas detected through O V, O VI, Ne VIII and Mg X absorption associated with the QSO HE 0238 - 1904 (z_em ~ 0.629). Based on the similarities in the absorption line profiles and estimated covering fractions, we find that the O VI and Ne VIII absorption trace the same phase of the absorbing gas. Simple photoionization models can reproduce the observed N(Ne VIII), N(O VI) and N(Mg X) from a single phase whereas the low ionization species (e.g. N III, N IV, O IV) originate from a different phase. The measured N(Ne VIII)/N(O VI) ratio is found to be remarkably similar (within a factor of ~ 2) in several individual absorption components kinematically spread over ~ 1800 km/s. Under photoionization this requires a fine tuning between hydrogen density (nH) and the distance of the absorbing gas from the QSO. Alternatively this can also be explained by collisional ionization in hot gas with T > 10^{5.7} K. Long-term stability favors the absorbing gas being located outside the broad line region (BLR). We speculate that the collimated flow of such a hot gas could possibly be triggered by the radio jet interaction.Comment: Minor revision (accepted for publication in MNRAS letter