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We present moderately high-resolution echelle observations of the nucleus of NGC 5195, the line of sight to which samples intervening interstellar material associated with the outer spiral arm of M51. Our spectra reveal absorption from interstellar Na i, K i, Ca ii, and CH+, and from a number of diffuse interstellar bands (DIBs), at a velocity close to that exhibited by H i 21 cm emission from M51 at the position of NGC 5195. The H i column density implied by the equivalent width of the λ5780.5 DIB, based on the relationship between Wλ(5780.5) and N(H i) derived for sight lines in the local Galactic interstellar medium, is consistent with the column density obtained from the integrated H i emission. The H2 column density predicted from the observed column density of K i, using the Galactic relationship between N (K i) and N(H2), is comparable to N (H i), suggesting a high molecular fraction (∼0.65) for the M51 gas toward NGC 5195. The DIBs toward NGC 5195 are, on average, ∼40% weaker than would be expected based on the K i column density, a further indication that the gas in this direction has a high molecular content. The M51 material is characterized also by a high N(Na i)/N(Ca ii) ratio (≳11), indicative of a high degree of Ca depletion, and a high Wλ(5797.1)/Wλ(5780.5) ratio (∼1.6), suggestive of either a very weak ambient radiation field or a significantly shielded environment. A high N(CH+)/N(CH) ratio (≳2.3) for the M51 material toward NGC 5195 may be the result of enhanced turbulence due to interactions between M51 and its companion.

We present new radial velocity curves for δ Cephei as a preliminary example for a series of papers on cepheids with periods from 10 to 20 days. The data are provided by the echelle spectrograph of the Apache Point Observatory 3.5-m telescope. Separate velocities are shown for lines formed at distinctly different optical depths. New data for the Paschen lines, the O i triplet at 7773 Å, and the Ca ii infrared triplet are included.

We present an analysis of interstellar absorption lines in high-resolution optical echelle spectra of SS Cyg obtained during an outburst in 2013 June and in archival Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer data. The Ca II K and Na I D lines toward SS Cyg are compared with those toward nearby B and A stars in an effort to place constraints on the distance to SS Cyg. We find that the distance constraints are not very robust from this method due to the rather slow increase in neutral gas column density with distance and the scatter in the column densities from one sight line to another. However, the optical absorption-line measurements allow us to derive a precise estimate for the line-of-sight reddening of E(B -V) = 0.020 + or - 0.005 mag. Furthermore, our analysis of the absorption lines of O I, Si II, P II, and Fe II seen in the UV spectra yields an estimate of the H I column density and depletion strength in this direction.

We present an analysis of interstellar absorption lines in high-resolution optical echelle spectra of SS Cyg obtained during an outburst in 2013 June and in archivalHubble Space TelescopeandFar Ultraviolet Spectroscopic Explorerdata. The CaiiK and NaiD lines toward SS Cyg are compared with those toward nearby B and A stars in an effort to place constraints on the distance to SS Cyg. We find that the distance constraints are not very robust from this method due to the rather slow increase in neutral gas column density with distance and the scatter in the column densities from one sight line to another. However, the optical absorption-line measurements allow us to derive a precise estimate for the line-of-sight reddening ofE(B - V) = 0.020 ± 0.005 mag. Furthermore, our analysis of the absorption lines of Oi, Siii, Pii, and Feiiseen in the UV spectra yields an estimate of the Hicolumn density and depletion strength in this direction.

We present preliminary results of a detailed chemical abundance analysis for a sample of solar-type stars known to exhibit excess infrared emission associated with dusty debris disks. Our sample of 28 stars was selected based on results from the Formation and Evolution of Planetary Systems (FEPS) Spitzer Legacy Program, for the purpose of investigating whether the stellar atmospheres have been polluted with planetary material, which could indicate that the metallicity enhancement in stars with planets is due to metal-rich infall in the later stages of star and planet formation. The preliminary results presented here consist of precise abundances for 15 elements (C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Fe, Co, and Ni) for half of the stars in our sample. We find that none of the stars investigated so far exhibit the expected trend of increasing elemental abundance with increasing condensation temperature, which would result from the stars having accreted planetary debris. Rather, the slopes of linear least-squares fits to the abundance data are either negative or consistent with zero. In both cases, our results may indicate that, like the Sun, the debris disk host stars are deficient in refractory elements, a possible signature of terrestrial and/or gas giant planet formation.

We present an analysis of interstellar absorption lines in high-resolution optical echelle spectra of SS Cyg obtained during an outburst in 2013 June and in archival Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer data. The Ca ii K and Na i D lines toward SS Cyg are compared with those toward nearby B and A stars in an effort to place constraints on the distance to SS Cyg. We find that the distance constraints are not very robust from this method due to the rather slow increase in neutral gas column density with distance and the scatter in the column densities from one sight line to another. However, the optical absorption-line measurements allow us to derive a precise estimate for the line-of-sight reddening of E(B - V) = 0.020 ± 0.005 mag. Furthermore, our analysis of the absorption lines of O i, Si ii, P ii, and Fe ii seen in the UV spectra yields an estimate of the H i column density and depletion strength in this direction.

We present a comprehensive survey of B abundances in diffuse interstellar clouds from HST/STIS observations along 56 Galactic sight lines. Our sample is the result of a complete search of archival STIS data for the B II λ1362 resonance line, with each detection confirmed by the presence of absorption from other dominant ions at the same velocity. The data probe a range of astrophysical environments including both high-density regions of massive star formation as well as low-density paths through the Galactic halo, allowing us to clearly define the trend of B depletion onto interstellar grains as a function of gas density. Many extended sight lines exhibit complex absorption profiles that trace both local gas and gas associated with either the Sagittarius-Carina or Perseus spiral arm. Our analysis indicates a higher B/O ratio in the inner Sagittarius-Carina spiral arm than in the vicinity of the Sun, which may suggest that B production in the current epoch is dominated by a secondary process. The average gas-phase B abundance in the warm diffuse ISM [log ϵ(B) = 2.38±0.10] is consistent with the abundances determined for a variety of Galactic disk stars, but is depleted by 60% relative to the solar system value. Our survey also reveals sight lines with enhanced B abundances that potentially trace recent production of 11B either by cosmic-ray or neutrino-induced spallation. Such sight lines will be key to discerning the relative importance of the two production routes for 11B synthesis.

We present an analysis of moderately high resolution optical spectra obtained for the sight line to CD-23 13777, an O9 supergiant that probes high velocity interstellar gas associated with the supernova remnant W28. Absorption components at both high positive and high negative velocity are seen in the interstellar Na I D and Ca II H and K lines toward CD-23 13777. The high velocity components exhibit low Na I/Ca II ratios, suggesting efficient grain destruction by shock sputtering. High column densities of CH+, and high CH+/CH ratios, for the components seen at lower velocity may be indicative of enhanced turbulence in the clouds interacting with W28. The highest positive and negative velocities of the components seen in Na I and Ca II absorption toward CD-23 13777 imply that the velocity of the blast wave associated with W28 is at least 150 km/s, a value that is significantly higher than most previous estimates. The line of sight to CD-23 13777 passes very close to a well-known site of interaction between the SNR and a molecular cloud to the northeast. The northeast molecular cloud exhibits broad molecular line emission, OH maser emission from numerous locations, and bright extended GeV and TeV gamma-ray emission. The sight line to CD-23 13777 is thus a unique and valuable probe of the interaction between W28 and dense molecular gas in its environs. Future observations at UV and visible wavelengths will help to better constrain the abundances, kinematics, and physical conditions in the shocked and quiescent gas along this line of sight.

We present the results of lifetime measurements made using beam-foil techniques on levels of astrophysical interest in Pb II producing lines at 1203.6 A (\\(6s6p^{2}\\) \\(^{2}D_{3/2}\\)) and 1433.9 A (\\(6s^{2}6d\\) \\(^{2}D_{3/2}\\)). We also report the first detection of the Pb II \\(\\lambda1203\\) line in the interstellar medium (ISM) from an analysis of archival spectra acquired by the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). The oscillator strengths derived from our experimental lifetimes for Pb II \\(\\lambda\\lambda1203\\), \\(1433\\) are generally consistent with recent theoretical results, including our own relativistic calculations. Our analysis of high-resolution HST/STIS spectra helps to confirm the relative strengths of the Pb II \\(\\lambda\\lambda 1203\\), \\(1433\\) lines. However, the oscillator strength that we obtain for Pb II \\(\\lambda1433\\) (\\(0.321\\pm0.034\\)) is significantly smaller than earlier theoretical values, which have been used to study the abundance of Pb in the ISM. Our revised oscillator strength for \\(\\lambda1433\\) yields an increase in the interstellar abundance of Pb of 0.43 dex over determinations based on the value given by Morton, indicating that the depletion of Pb onto interstellar dust grains is less severe than previously thought.

We present a comprehensive examination of interstellar P and Cl abundances based on an analysis of archival spectra acquired with the Space Telescope Imaging Spectrograph of the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. Column densities of P II, Cl I, and Cl II are determined for a combined sample of 107 sight lines probing diffuse atomic and molecular gas in the local Galactic interstellar medium (ISM). We reevaluate the nearly linear relationship between the column densities of Cl I and H\\(_2\\), which arises from the rapid conversion of Cl\\(^+\\) to Cl\\(^0\\) in regions where H\\(_2\\) is abundant. Using the observed total gas-phase P and Cl abundances, we derive depletion parameters for these elements, adopting the methodology of Jenkins. We find that both P and Cl are essentially undepleted along sight lines showing the lowest overall depletions. Increasingly severe depletions of P are seen along molecule-rich sight lines. In contrast, gas-phase Cl abundances show no systematic variation with molecular hydrogen fraction. However, enhanced Cl (and P) depletion rates are found for a subset of sight lines showing elevated levels of Cl ionization. An analysis of neutral chlorine fractions yields estimates for the amount of atomic hydrogen associated with the H\\(_2\\)-bearing gas in each direction. These results indicate that the molecular fraction in the H\\(_2\\)-bearing gas is at least 10% for all sight lines with \\(\\log N({\\rm H}_2)\\gtrsim18\\) and that the gas is essentially fully molecular at \\(\\log N({\\rm H}_2)\\approx21\\).