arXiv subjects

Jerry Edelstein

Publications and source records attributed to Jerry Edelstein.

46 records · Page 3Linked to original sources

arXiv2006

Diffuse Far-ultraviolet Observation of the Lupus Loop Region

Diffuse far-ultraviolet (FUV) emissions from the Lupus Loop region (SNR 330.0+15.0) have been observed with Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR), also known as Far-ultraviolet IMaging Spectrograph (FIMS). We have detected several important ionic lines, including Si II*, C IV, and N IV], which characterize the warm, hot ionized gas in this region. The spatial variations in the line intensities of Si II* and C IV have also been studied in comparison with X-ray and dust observations. The result shows that they originate from the interface between the hot gas seen in the X-ray and the cooler H I shell with which dust is associated. The interface is rather diffuse, and the gases with different temperatures seem to co-exist in this region. A shock may exist upfront in the interface, but its velocity should be very small as no shock-related distinguished feature is seen in Ha.

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arXiv2006

Far-ultraviolet Observations of the North Ecliptic Pole with SPEAR

We present SPEAR/FIMS far-ultraviolet observations near the North Ecliptic Pole. This area, at b~30 degrees and with intermediate HI column, seems to be a fairly typical line of sight that is representative of general processes in the diffuse ISM. We detect a surprising number of emission lines of many elements at various ionization states representing gas phases from the warm neutral medium (WNM) to the hot ionized medium (HIM). We also detect fluorescence bands of H2, which may be due to the ubiquitous diffuse H2 previously observed in absorption.

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arXiv2006

SPEAR Far Ultraviolet Spectral Images of the Cygnus Loop

We present far-ultraviolet (FUV) spectral images, measured at C IV 1550, He II 1640, Si IV+O IV] 1400, and O III] 1664, of the entire Cygnus Loop, observed with the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR) instrument, also known as FIMS. The spatial distribution of FUV emission generally corresponds with a limb-brightened shell, and is similar to optical, radio and X-ray images. The features found in the present work include a ``carrot'', diffuse interior, and breakout features, which have not been seen in previous FUV studies. Shock velocities of 140-160 km/s is found from a line ratio of O IV] to O III], which is insensitive not only to resonance scattering but also to elemental abundance. The estimated velocity indicates that the fast shocks are widespread across the remnant. By comparing various line ratios with steady-state shock models, it is also shown that the resonance scattering is widespread.

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arXiv2006

The SPEAR Instrument and On-Orbit Performance

The SPEAR (or 'FIMS') instrumentation has been used to conduct the first large-scale spectral mapping of diffuse cosmic far ultraviolet (FUV, 900-1750 AA) emission, including important diagnostics of interstellar hot (10^4 K - 10^6 K) and photoionized plasmas, H_2, and dust scattered starlight. The instrumentation's performance has allowed for the unprecedented detection of astrophysical diffuse far UV emission lines. A spectral resolution of 550 and an imaging resolution of 5' is achieved on-orbit in the Short (900 - 1175 AA) and Long (1335 - 1750 AA) bandpass channels within their respective 7.4 deg x 4.3' and 4.0 deg x 4.6' fields of view. We describe the SPEAR imaging spectrographs, their performance, and the nature and handling of their data.

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arXiv2000

Reanalyses of Voyager Ultraviolet Spectrometer Limits to the EUV and FUV Diffuse Astronomical Flux

We re-examine {\em Voyager} Ultraviolet Spectrograph data used to establish upper limits to the $λ$ 500-900 Åand $λ$ 900-1100 Åcosmic diffuse background. The measurement of diffuse flux with the {\em Voyager} UVS data requires complex corrections for noise sources which are far larger than the astronomical signal. In the analyses carried out to date, the upper limits obtained on the diffuse background show statistical anomalies which indicate that substantial systematic errors are present. We detail these anomalies and identify specific problems with the analysis. We derive statistically robust 2~$σ$ upper limits for continuum flux of 570~photons~s$^{-1}$ cm$^{-2}$~ster$^{-1}$~Å$^{-1}$ and for the 1000 Å~ diffuse line flux of 11,790~photons~s$^{-1}$ cm$^{-2}$~ster$^{-1}$. The true limits may be substantially higher because of unknown systematic uncertainties. The new statistical limits alone are insufficient to support previous conclusions based on the {\em Voyager} data including work on the character of interstellar dust and estimates of the diffuse extragalactic far UV background as absorbed by intergalactic dust.

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arXiv1999

PSR B0656+14: Combined Optical, X-ray & EUV Studies

PSR B0656+14's high energy emission is consistent with that of combined magnetospheric and thermal (surface & polar cap) emission. Uncertainties with the radio-derived distance and X-ray instrumentation sensitivities complicate a definitive thermal characterisation however. A re-analysis of combined ROSAT/EUVE archival data in conjunction with integrated & phase-resolved optical photometry is shown to constrain this characterisation.

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arXiv1999

Far Ultraviolet Absolute Flux of alpha Virginis

We present the far ultraviolet spectrum of alpha Virginis taken with EURD spectrograph on-board MINISAT-01. The spectral range covered is from ~900 to 1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE spectra of alpha Vir and compared the extension of the model to our wavelengths with EURD data. This comparison shows that EURD fluxes are consistent with the prediction of the model within 20-30%, depending on the reddening assumed. EURD fluxes are consistent with Voyager observations but are ~60% higher than most previous rocket observations of alpha Vir.

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arXiv1999

Evidence Against the Sciama Model of Radiative Decay of Massive Neutrinos

We report on spectral observations of the night sky in the band around 900 angstroms where the emission line in the Sciama model of radiatively decaying massive neutrinos would be present. The data were obtained with a high resolution, high sensitivity spectrometer flown on the Spanish MINISAT satellite. The observed emission is far less intense than that expected in the Sciama model.

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arXiv1998

Far-Ultraviolet Performance of the Berkeley Spectrograph During the ORFEUS-SPAS II Mission

The Berkeley spectrograph aboard the ORFEUS telescope made its second flight on the 14-day ORFEUS-SPAS II mission of the Space Shuttle Columbia in November/December 1996. Approximately half of the available observing time was dedicated to the Berkeley spectrograph, which was used by both Principal and Guest Investigators. The spectrograph's full bandpass is 390-1218 A; here we discuss its in-flight performance at far-ultraviolet (FUV) wavelengths, where most of the observations were performed. The instrument's effective area peaks at 8.9 +/- 0.5 cm^2 near 1020 A, and the mean spectral resolution is 95 km/s FWHM for point sources. Over most of the spectral range, the typical night-time background event rate in each spectral resolution element was about 0.003/s. Simultaneous background observations of an adjacent blank field were provided through a secondary, off-axis aperture. The Berkeley spectrograph's unique combination of sensitivity and resolution provided valuable observations of approximately 105 distinct astronomical targets, ranging in distance from the earth's own moon to some of the brightest AGN.

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arXiv1998

Spectral Observations of Diffuse Far-Ultraviolet Emission from the Hot Phase of the Interstellar Medium with the Diffuse Ultraviolet Experiment

One of the keys to interpreting the character and evolution of interstellar matter in the galaxy is understanding the distribution of the low density hot (10^5 K -10^6 K) phase of the interstellar medium (ISM). This phase is much more difficult to observe than the cooler high density components of the ISM because of its low density and lack of easily observable tracers. Because gas of this temperature emits mainly in the far ultraviolet (912 angstrom - 1800 angstroms) and extreme ultraviolet (80 angstrom - 912 angstrom), and (for gas hotter than 10^6 K) X-rays, observations in these bands can provide important constraints to the distribution of this gas. Because of interstellar opacity at EUV wavelengths, only FUV and X-ray observations can provide clues to the properties of hot gas from distant regions. We present results from a search for FUV emission from the diffuse ISM conducted with an orbital FUV spectrometer, DUVE, which was launched in July, 1992. The DUVE spectrometer, which covers the band from 950 angstrom to 1080 angstrom with 3.2 angstrom resolution, observed a region of low neutral hydrogen column density near the south galactic pole for a total effective integration time of 1583 seconds. The only emission line detected was a geocoronal hydrogen line at 1025 angstrom. We are able to place upper limits to several expected emission features that provide constraints on interstellar plasma parameters. We are also able to place limits on the continuum emission throughout the bandpass. We compare these limits and other diffuse observations with several models of the structure of the interstellar medium and discuss the ramifications.

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