High-Resolution Spectroscopy of the Lunar Sodium Exosphere

We have applied high-resolution Fabry-Perot spectroscopy to the study of the lunar sodium exosphere for the study of exospheric effective temperature and velocity variations. Observing from the National Solar Observatory McMath-Pierce Telescope, we used a dual-etalon Fabry-Perot spectrometer with a resolving power of 180,000 to measure line widths and Doppler shifts of the sodium D2 (5889.95 ) emission line. Our field of view was 360 km, and measurements were made in equatorial and polar regions from 500 km to 3500 km off the limb. Data were obtained from full moon to 3 days following full moon (waning phase) in March 2009. Measured Doppler line widths within 1100 km of the sunlit east and south lunar limbs for observations between 5 and 40 deg lunar phase imply effective temperatures ranging between 3260 +/- 190 and 1000 +/- 135 K. Preliminary line center analysis indicates velocity displacements between different locations off the lunar limb ranging between 100 and 600 m/s from the lunar rest velocity with a precision of +/-20 to +/-50 m/s depending on brightness. Based on the success of these exploratory observations, an extensive program has been initiated that is expected to constrain lunar atmospheric and surface-process modeling and help quantify source and escape mechanisms

A Search for Intrinsic Polarization in O Stars with Variable Winds

New observations of 9 of the brightest northern O stars have been made with the Breger polarimeter on the 0.9~m telescope at McDonald Observatory and the AnyPol polarimeter on the 0.4~m telescope at Limber Observatory, using the Johnson-Cousins UBVRI broadband filter system. Comparison with earlier measurements shows no clearly defined long-term polarization variability. For all 9 stars the wavelength dependence of the degree of polarization in the optical range can be fit by a normal interstellar polarization law. The polarization position angles are practically constant with wavelength and are consistent with those of neighboring stars. Thus the simplest conclusion is that the polarization of all the program stars is primarily interstellar. The O stars chosen for this study are generally known from ultraviolet and optical spectroscopy to have substantial mass loss rates and variable winds, as well as occasional circumstellar emission. Their lack of intrinsic polarization in comparison with the similar Be stars may be explained by the dominance of radiation as a wind driving force due to higher luminosity, which results in lower density and less rotational flattening in the electron scattering inner envelopes where the polarization is produced. However, time series of polarization measurements taken simultaneously with H-alpha and UV spectroscopy during several coordinated multiwavelength campaigns suggest two cases of possible small-amplitude, periodic short-term polarization variability, and therefore intrinsic polarization, which may be correlated with the more widely recognized spectroscopic variations.Comment: LaTeX2e, 22 pages including 11 tables; 12 separate gif figures; uses aastex.cls preprint package; accepted by The Astronomical Journa

Polarimetric Evidence of Non-Spherical Winds

Polarization observations yield otherwise unobtainable information about the geometrical structure of unresolved objects. In this talk we review the evidences for non-spherically symmetric structures around Luminous Hot Stars from polarimetry and what we can learn with this technique. Polarimetry has added a new dimension to the study of the envelopes of Luminous Blue Variables, Wolf-Rayet stars and B[e] stars, all of which are discussed in some detail.Comment: 8 pages, 2 encapsulated Postscript figures, uses lamuphys.sty. Invited review to appear in IAU Coll. 169, Variable and Non-Spherical Stellar Winds in Luminous Hot Stars, eds. B. Wolf, A.Fullerton and O. Stahl (Springer

High Resolution Spectroscopy of the Lunar Sodium Exosphere

We conducted a highly successful engineering run to demonstrate the feasibility of high spectral resolution observations of the lunar exosphere. From the National Solar Observatory McMath-Pierce telscope, we used a dual etalon Fabry-Perot spectometer (R = 200,000) to measure the velocity and line width of the Na D2 (5889.950 A) emission line. We observe the intensity in equatorial and polar regions from 420 km to 2 lunar radii ( 3500 km) off the limb with a 3 arcmin (360 km) field of view. The observations were made in March 2009 at full moon to 3 days after full moon. Preliminary results indicate we can measure and, in fact, see velocity displacements between different locations of 0.25 km/s. The deconvolved line width is 2 km/s. Future plans include higher velocity-resolved line profile observations (R=300,00) under different lunar phases including in and out of the Earth\u27s magnetotail and measurements at different altitudes and latitudes to explore factors that link observed morphologies and dynamics to the sources, sinks, and escape of the lunar atmosphere. These observations will help constrain atmospheric and surface-process modeling, and help quantify source and escape mechanisms

High-Spectral Resolution, May 2013 Ground-Based Observations of the Lunar Sodium and Potassium Exosphere

We apply high resolution spectroscopy to investigate the lunar exosphere by measuring sodium and potassium spectral line profiles to determine the variations in exospheric effective temperatures and velocities as a function of time, solar conditions and geometries. Observations are made with a dual-etalon Fabry-Perot spectrometer from the National Solar Observatory McMath-Pierce Telescope. The spectrometer has a Field of View (FOV) of 3 arcmin (~336 km at semimajor axis = 384,400 km) and a resolving power of 180,000 and 150,000 to measure the line widths and radial velocity Doppler shifts of the sodium D2 (5889.951 Å) and potassium D1 (7698.965 Å) emission lines, respectively. We first measured the sodium profile in March 2009 [1] followed by the first potassium line profile measurements in June 2012 (Fig. 1) during the moon’s waning gibbous phase. As previously reported [2], [3] potassium has a smaller scale height than sodium (Fig. 1). We only detected the potassium emission within ~0.25 Rmoon of the lunar limb while we measure sodium out to ~1 Rmoon. A lunar scattered light gradient underlying the FabryPerot circular interference fringes is the dominant continuum source and limiting factors in the precision of these measurements