L. Wallace

Medium-Resolution Spectra of Normal Stars in the K Band

An Atlas of 115 medium-resolution K-band (2.0-2.4 μm) stellar spectra, spanning spectral types O-M and luminosity types I-V, is presented. K-band spectra are also presented for one N- and one J-type carbon star. A time series of spectra is presented for an S-type Mira variable. All the spectra are at a resolution of ~3000 (1.4 cm-1) and have had the terrestrial absorption removed by dividing by a featureless spectrum. The spectra are plotted with the major spectral features identified and are available digitally.

An Optical and Near-infrared (2958-9250 Å) Solar Flux Atlas

A line resolved (R = λ/Δλ ~ 350,000-700,000) solar flux atlas covering the region ~2958-9250 A is discussed. The atlas has been prepared from ground-based spectra. The telluric spectrum was derived from disk-center solar spectra taken at differing airmasses. This telluric spectrum was removed from the flux spectrum. Identifications are provided for solar lines. Both the data and plots with line identifications are available digitally.

On the thermal structure of Uranus

Abstract Uranus has an effective temperature close to the solar equilibrium value and undoubtedly a thermal inversion of at least 140 K at a pressure of ∼3 dyn cm −2 . With the inversion and the thermal opacity provided by a HeH 2 mixture in a ratio close to solar abundance, acceptable agreement can be achieved with the available infrared observations. The cause of the inversion is, however, uncertain. The use of the HeH 2 opacity for Uranus is justified by the excellent agreement of the frequency variation of that opacity with the thermal spectrum of Jupiter.

The periods of Neptune: Evidence for atmospheric motions

Abstract An extended photometric time series in the J and K bands of Neptune has a complex appearance which appears to require the simultaneous presence of three periodicities plus related harmonics in the ( J - K ) color. The most apparent of the fundamental periods is N1 = 17.73 hr. The two others are at N2 = 18.56 and N3 = 18.29 hr and may be the result of amplitude modulation of a previously reported period of 18.42 hr. We interpret the presence of multiple periodicity as indicating that distinct systems of zonal winds exist on the planet. We argue that these wind systems are probably confined to moderate or high latitudes on the basis of recent omages of the planet taken in a spectral region of strong CH 4 absorption, and, by analogy to the zonal wind systems that exist in Jupiters atmosphere, deduce a period of rotation for the body of the planet of 18.2 ± 0.4 hr. Zonal wind contrasts of up to 109 m sec −1 are implied in the atmosphere of Neptune by these observations.

Detection of the 1.6 μm E 4Π-A 4Π FeH System in Sunspot and Cool Star Spectra

Lines of a previously undescribed molecular band have been identified in high-resolution spectra of sunspots and in the spectra of two M dwarfs and one L dwarf. This band has also been found in laboratory spectra of a source known to produce FeH. The band has a head at 1.583 μm (6317 cm-1) and is degraded to longer wavelengths. Based on observational evidence and a published predicted band position, it is suggested that this is the 0-0 band of the E 4Π-A 4Π system of FeH.

Spectra of Cool Stars in the J Band (1.0-1.3 μm) at Medium Resolution

A spectroscopic survey of 103 cool S-, C-, and M-type stars was undertaken with the Kitt Peak cryogenic spectrograph on the 1.3 m telescope to make a detailed search for new molecular bands in the 1.0–1.3 μm J-band region. While the spectra have high signal-to-noise ratios and good repeatability, no strong new features were found. Higher resolution spectra of a small sample of representative stars observed with the 4 m Fourier transform spectrometer were invoked in order to identify the features in these spectra. With few exceptions, the details of these spectra are well understood. Laboratory spectra were obtained to aid in the identification of some weak features. Spectral features from dominant lines of Ti, Fe, Al, Si, Mn, Na, and K, and molecular bands due to TiO, TiS, ZrO, ZrS, VO, H2O, and CN, have been identified in the spectra. Several weak unidentified bands are found.

The seasonal variation of the thermal structure of the atmosphere of Uranus

Abstract A series of time-dependent radiative/convective models are presented for the atmosphere of Uranus. The effects of atmospheric dynamics have been omitted from the models. The inclination of the pole of rotation to the pole of the orbit, approximately 90°, produces large seasonal changes in the insolation. Because of the relatively small flow of heat from the interior, these seasonal changes cause the effective temperature, which is about 60°K, to vary through the 84-year orbital period by ∼5°K at the poles, ∼4°K at ±60° latitude, ∼2°K at ±30° latitude, and ∼0.5°K at the equator. For a particular latitude, the minimum effective temperature and the maximum convective flow of heat from the interior occur near the end of the period when the sun remains below the horizon during the Uranian day. If the methane mixing ratio is not limited by its saturated vapor pressure (SVP) in the convective region, the maximum convective flow would be a few times the orbital average convective flow and persist for an interval of several years. On the other hand, if the methane mixing ratio is limited by its SVP in the convective regions, the maximum convective flow could be orders of magnitude greater than the orbital average and could persist for less than an hour. If the orbital mean internal heat flow is negligible, the difference in effective temperatures between 30 and 60° latitude would be in the range 2 to 4°K. If the internal heat is taken to be about the maximum allowable and is assumed to be redistributed in the interior in a manner to compensate for the minimum in insolation at low latitudes, the corresponding temperature difference would be in the range 1 2 to 2°K. In either case, the existing theory of atmospheric dynamics for the outer planets indicates that such large temperature differences will drive large-scale motions which would in turn reduce these temperature differences.

The near-infrared spectrum of a Th/Ar hollow cathode lamp

Abstract An analysis is presented for a Th/Ar hollow cathode spectrum covering the 1798– 9180 cm −1 region of the near-infrared. The wave numbers and intensities of the lines should be of use in the calibration of spectra as well as in the level analysis of atomic thorium.

Wavelength Calibration of Near-Infrared Spectra

An atlas of a thorium-argon hollow cathode lamp in selected intervals of the 1-2.5 mm region is presented. Accurate wavelengths of the ∼500 lines recorded are given in a table. This material is intended for wavelength calibration of near-infrared spectra and is especially critical for high-resolution work.

Medium-Resolution Stellar Spectra in the L Band from 2400 to 3000 cm−1 (3.3 to 4.2 Microns)

We present a brief atlas of L-band (3.3–4.2 μm) spectra for 42 stars plus the Sun and a sunspot observed at a resolving power of R ~ 3000. This contribution is intended to supplement our previous K-band, H-band, and J-band spectral atlases. The L-band data, which cover some or all of the 2400 to 3000 cm-1 (3.3–4.2 μm) region, are mainly for luminous late-type stars. In reducing these data, special care has been taken to remove telluric features, especially water vapor. We identify temperature- and luminosity-sensitive atomic and molecular indices to aid in the classification of stellar spectra in the L band. The data are available electronically.