A5027535889- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Atmospheric Ozone and Climate
- Atomic and Molecular Physics
- Astronomical Observations and Instrumentation
- Ionosphere and magnetosphere dynamics
- Spectroscopy and Laser Applications
- Geophysics and Gravity Measurements
- Nuclear physics research studies
- Solar and Space Plasma Dynamics
- Isotope Analysis in Ecology
- Spacecraft and Cryogenic Technologies
- Nuclear Physics and Applications
- Molecular Spectroscopy and Structure
- Atmospheric and Environmental Gas Dynamics
- Astronomy and Astrophysical Research
- Advanced Chemical Physics Studies
- Scientific Measurement and Uncertainty Evaluation
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Astronomical and nuclear sciences
- History and advancements in chemistry
- Radioactive contamination and transfer
- Gamma-ray bursts and supernovae
Woodlawn School
2017
Johns Hopkins University
2003-2009
Northwestern University
2005-2006
University of Toledo
1997-2003
The University of Texas at Austin
2000-2003
Analyses of spectra obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, together from Copernicus and interstellar medium absorption profile spectrograph (IMAPS) instruments, reveal an unexplained, very wide range in observed deuterium/hydrogen (D/H) ratios for gas Galactic disk beyond Local Bubble. We argue that spatial variations depletion deuterium onto dust grains can explain these local gas-phase D/H ratios. present a variable model naturally explains constant...
The bright star delta Sco has been considered a typical B0-type object for many years. Spectra of the published prior to 1990 showed no evidence emission, but only short-term line profile variations attributed nonradial pulsations. Speckle interferometric observations show that is binary system with highly-eccentric orbit and period 10.6 Weak emission in H-alpha was detected its spectrum first time during periastron passage 1990. Shortly before next summer 2000, entered strong enhanced mass...
We have carried out an investigation of the abundance deuterium along two extended sight lines through interstellar medium (ISM) Galactic disk. The data include Far Ultraviolet Spectroscopic Explorer (FUSE) observations HD 195965 (B1 Ib) and 191877 (B0 V), as well Space Telescope Imaging Spectrograph (STIS) 195965. distances to 191877, derived from spectroscopic parallax, are 794 ± 200 2200 550 pc, respectively, making these longest disk in which has been investigated with FUSE. FUSE spectra...
In an effort to probe the extent of variations in interstellar 7Li/6Li ratio seen previously, ultra-high-resolution (R ~ 360,000), high signal-to-noise spectra stars Perseus OB2 and Scorpius associations were obtained. These measurements confirm our earlier findings about 2 toward o Per, value predicted from models Galactic cosmic-ray spallation reactions. Observations other nearby yield limits consistent with isotopic ~12 carbonaceous chondrite meteorites. If this originally represented gas...
We present the results of a spectroscopic monitoring program binary system δ Scorpii, whose primary became Be star after last periastron encounter in Summer 2000. The observations cover period 2 years (March 2001–June 2003) and are continuation our previous campaign reported Miroshnichenko et al. ([CITE]). found that emission-line spectrum was gradually strengthening over whole period. Several short-term increases line emission, possibly due to outbursts matter ejected from stellar surface,...
The isotopic ratio 11B/10B of gas in diffuse interstellar clouds toward ζ Oph, κ Ori, and δ Sco is measured using HST/Goddard High Resolution Spectrograph echelle spectra the B II 1362 Å line. To within errors measurement, three lines sight give identical results for a mean value = 3.4 ± 0.7, quite similar to solar system 4.05. These show that latter not highly anomalous higher than 2.5, as predicted boron produced from spallation reactions controlled by high-energy cosmic rays, most...
Band oscillator strengths for electronic transitions in CO were obtained at the Synchrotron Radiation Center of University Wisconsin-Madison. Our focus was on observed interstellar spectra with Far-Ultraviolet Spectroscopic Explorer; these are also important studies selective isotope photodissociation, where fractionation among isotopomers can occur. Absorption from ground state X1Σ+ (v'' = 0) to A1Π (v' 5), B1Σ+ 0, 1), C1Σ+ and E1Π measured. Fits A-X (5, band, whose strength is well known,...
We present the results of an optical spectroscopic study massive Wolf–Rayet (WR) binary HD 192641 = WR 137. These 1986–2000 data cover dust-formation maximum in 1997. Combining all available measurements radial velocities, we derive, for first time, a orbit with period 4766 ± 66 d (13.05 0.18 yr). The resulting masses, adopting i= 67 °, are MO= 20 2 M⊙ O component and MWR= 4.4 1.5 component. appear, respectively, approximately normal on low side given spectral types. Analysis intense...
Sensitive measurements of the interstellar gas-phase oxygen abundance have revealed a slight deficiency (~15%) toward stars within 500 pc Sun as compared to more distant sight lines. Recent FUSE observations nitrogen indicate larger variations, but no trends with distance were reported due significant measurement uncertainties for many By considering only highest quality (≥5 σ) N/O measurements, we find an intriguing trend in ratio distance. Toward seven ~500 Sun, weighted mean is 0.217 ±...
High-resolution optical spectra of HD 37903 and 147009, which illuminate the reflection nebulae NGC 2023 vdB 102, were obtained for comparison with our results 200775 7023. Ground-based measurements molecules CH, C2, CN atoms Na I K analyzed to extract physical conditions in foreground cloud. Estimates gas density, temperature, flux ultraviolet radiation derived compared from infrared radio studies main molecular The are similar those found diffuse clouds. material is less dense than cloud...
We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph observations of the weak interstellar N I λ1160 doublet toward 17 high-density sight lines [N(Htot) ≥ 1021 cm-2]. When combined with published data, our results reveal variations in fractional abundance showing a systematic deficiency at large N(Htot). At FUSE resolution (~20 km s-1), effects unresolved saturation cannot be conclusively ruled out, although O λ1356 shows little evidence...
We present Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph observations of high-ionization interstellar absorption toward HD 14434 [(l, b) = (135.1, -3.8); d ~ 2.3 kpc], an O5.5 V star in the Perseus OB1 Association. Intermediate-velocity Si IV C is at V_LSR -67 km/s, while low-ionization gas associated with arm detected -50 km/s. Neither N nor O VI km/s; although Al III Fe III, tracers warm ionized gas, are seen. The high-ion column densities km/s component...
The illuminating source of the photodissociation region associated with reflection nebula NGC 7023 is HD 200775. We probed foreground atomic and molecular material through diagnostics observed in absorption against background star. Ground-based measurements Na I, K Ca II molecules CH, CH+, C2, CN were analyzed order to extract physical conditions for this material. In particular, estimates gas density, temperature, flux ultraviolet radiation derived compared information obtained from maps...
The isotope ratio 85Rb/87Rb places constraints on models of the nucleosynthesis heavy elements, but there is no precise determination for material beyond solar system. We report first measurement interstellar Rb ratio. Our I line at 7800 Å diffuse gas toward ρ Oph A yields a value 1.21 ± 0.30 (1 σ) that differs significantly from meteoritic 2.59. Rb/K elemental abundance cloud also lower than seen in meteorites. Comparison 85Rb/K and 87Rb/K ratios with values indicates 85Rb this direction...
We present Far Ultraviolet Spectroscopic Explorer and ROSAT X-ray observations toward the Southern Coalsack. An almost complete halo can be seen around cloud in 0.75 1.5 keV images, most of observed stars show O VI absorption. Both have highly accurate distance determinations, allowing us to reliably place relative each other. Using these we find no VI-bearing gas foreground Coalsack, while for background cloud, absorption is norm. The column density correlates with intensities. These...
We present observations of interstellar rubidium toward o Per, ζ AE Aur, HD 147889, χ Oph, and 20 Aql. Theory suggests that stable 85Rb long-lived 87Rb are produced predominantly by high-mass stars, through a combination the weak s- r-processes. The 85Rb/87Rb ratio was determined from measurements Rb i line at 7800 Å compared to solar system meteoritic 2.59. Within 1σ uncertainties, all directions except 147889 have isotope ratios consistent with value. is much lower than value similar ρ Oph...
Abstract Measurements of the lithium isotopic ratio in diffuse interstellar medium from high-resolution spectra Li i λ 6708 resonance doublet have now been reported for a number lines sight. The majority results 7 Li/ 6 are similar to solar system 12.2, but line sight toward o Per, star near star-forming region IC 348, gave about two, expected value gas exposed spallation and fusion reactions driven by cosmic rays. To examine association 348 with rays more closely, we measured three stars...
As a part of study on the variation in 7Li/6Li ratio, high signal to noise, resolution spectroscopy Li I (6708 Angstroms) and K (4044 were obtained toward zeta o Per. The lithium isotope shift is approximately same as its fine structure splitting (0.158 Angstroms), resulting blend 7Li 6Li lines. Use line velocity template allowed straightforward determination isotopic ratio. Our observations show remarkably disparate ratios: = 1 0.6 +/- 2.9 Per 3.6 1.7 0.3 While results are consistent with...
We are conducting a survey on the 7 Li/ 6 Li ratio in interstellar space order to seek limits variation this ratio. The analysis is based technique we adopted extracting 11 B/ 10 B This uses line of comparable strength, from species likely occupy same volume cloud, as template for separating velocity components within profile. For our study ratio, K I at 4044 Å serves template. Our initial focus around star-forming region IC 348. high-resolution observations lines toward o and ζ Per show...