In the interstellar medium (ISM), molecular hydrogen is expected to form almost exclusively on the surfaces of dust grains. Due to that molecule's large formation energy (-4.5 eV), several dynamical effects are likely associated with the process, including the alignment of asymmetric dust grains with the ambient magnetic field. Such aligned dust grains are, in turn, believed to cause the broadband optical/infrared polarization observed in the ISM. Here, we present the first observational evidence for grain alignment driven by H-2 formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H-2 fluorescence. While our results strongly suggest a role for "Purcell rockets" in grain alignment, additional observations are needed to conclusively confirm their role. By showing a direct connection between H-2 formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H-2. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.

The GMT-Consortium Large Earth Finder (G-CLEF) will be part of the first generation instrumentation suite for the Giant Magellan Telescope (GMT). G-CLEF will be a general purpose optical passband echelle spectrograph with a precision radial velocity (PRV) capability of 10 cm/sec, a requirement necessary for the detection of Earth analogues. The instrument will be particularly sensitive to thermal effects and the necessary stability cannot be achieved through the use of low CTE materials alone. It is the combination of low CTE materials and exquisite thermal control which will enable the instrument to achieve its precision requirements.

Transition metal borides are known due to their attractive mechanical, electronic, refractive, and other properties. A new class of rhenium borides was identified by synchrotron single-crystal X-ray diffraction experiments in laser-heated diamond anvil cells between 26 and 75 GPa. Recoverable to ambient conditions, compounds rhenium triboride (ReB3) and rhenium tetraboride (ReB4) consist of close-packed single layers of rhenium atoms alternating with boron networks built from puckered hexagonal layers, which link short bonded (similar to 1.7 angstrom) axially oriented B-2 dumbbells. The short and incompressible Re-B and B-B bonds oriented along the hexagonal c-axis contribute to low axial compressibility comparable with the linear compressibility of diamond. Sub-millimeter samples of ReB3 and ReB4 were synthesized in a large-volume press at pressures as low as 33 GPa and used for material characterization. Crystals of both compounds are metallic and hard (Vickers hardness, H-V = 34(3) GPa). Geometrical, crystal-chemical, and theoretical analysis considerations suggest that potential ReBx compounds with x > 4 can be based on the same principle of structural organization as in ReB3 and ReB4 and possess similar mechanical and electronic properties.

Following our discovery of 2001 QT(297) as the second known binary Edgeworth - Kuiper Belt Object (EKBO) in October of 2001 [IAUC 7733], we have carried out additional high spatial resolution ground based imaging in October and November of 2001 and July, August, and September of 2002. Using the Raymond and Beverly Sackler Magellan Instant Camera (MagIC) on the Baade and Clay 6.5 m telescopes at Las Campanas Observatory in Chile, we have obtained accurate astrometric and photometric measurements in the Sloan r', i', and g' filters. Superb seeing conditions and PSF fitting allow an accurate determination of the binary component separation and position angle over time as well as a detailed study of color and temporal variability of the individual components. Here we present a physical characterization of the individual components of 2001 QT297 based on these astrometric, color and variability measurements. We find the primary to exhibit colors about 0.3 magnitudes redder than solar with no evidence for variability. The secondary component, however, exhibits strong variability (similar to0.6 magnitudes) with a best fit period of 4.7526 +/- 0.0007 h for a single peak lightcurve or 9.505 +/- 0.001 h for a dual peaked lightcurve. The colors measured for the secondary also suggest variability. Based on a preliminary orbit fit for the pair using observations spanning a one year arc, we are able to estimate a system mass of similar to 3.2 x 10(18) kg and provide constraints to the surface albedo of 9-14% for assumed densities between 1 and 2 g/cm(3).

We present Keck/NIRSPEC near-IR images and Magellan/IMACS optical spectroscopy of the host galaxy of GRB 031203. The host is an actively star-forming galaxy at z=0.1055+/-0.0001. This is the lowest redshift GRB to date, aside from GRB 980425. From the hydrogen Balmer lines, we infer an extinction of A(V)=3.62+/-0.25 or a total reddening E-T (B-V)=1.17+/-0.1 toward the sight line to the nebular regions. After correcting for reddening, we perform an emission-line analysis and derive an ISM temperature of T =13400+/-2000 K and electron density of n(e)=300 cm(-3). These imply a metallicity [O/H]=-0.72+/-0.15 dex and a roughly solar abundance pattern for N, Ne, S, and Ar. Integrating Halpha, we infer a dust-corrected star formation rate (SFR) of more than 11 M-circle dot yr(-1). These observations have the following implications: (1) The galaxy has a low K'-band luminosity Lapproximate toL*(K)/5, typical of GRB host galaxies. (2) The low redshift indicates GRB 031203 had an isotropic-equivalent gamma-ray energy release smaller than all previous confirmed GRB events. The burst discovery raises the likelihood of identifying many additional low-z, low-flux events with Swift. (3) The large SFR, low metallicity, and inferred hard radiation field are suggestive of massive star formation, supporting the collapsar model. (4) Several lines of evidence argue against the identification of GRB 031203 as an X-ray flash event.

We present deep optical photometry of the afterglow of gamma-ray burst (GRB) 041006 and its associated hypernova obtained over 65 days after detection (55 R-band epochs on 10 different nights). Our early data (t < days) joined with published GCN data indicate a steepening decay, approaching F(v) proportional to t(-0.6) at early times (t << day) and at late times. The break at days is the earliest reported jet break among all GRB afterglows. During our first night, we obtained 39 exposures spanning 2.15 hr from 0.62 to 0.71 days after the burst that reveal a smooth afterglow, with an rms deviation of 0.024 mag from the local power-law fit, consistent with photometric errors. After days, the decay slows considerably, and the light curve remains approximately flat at mag t similar to 4 R similar to 24 for a month before decaying by another magnitude to reach mag 2 months after the burst. This "bump" is R similar to 25 well fit by a k-corrected light curve of supernova SN 1998bw, but only if stretched by a factor of 1.38 in time. In comparison with the other GRB-related SN bumps, GRB 041006 stakes out new parameter space for GRBs/SNe, with a very bright and significantly stretched late-time SN light curve. Within a small sample of fairly well observed GRB/SN bumps, we see a hint of a possible correlation between their peak luminosity and their "stretch factor," broadly similar to the well-studied Phillips relation for the Type Ia supernovae.

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempet 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.

We present an analysis of Hapke photometric modeling applied to uniform ground-based UBVRIJHK broadband data of asteroid 25143 Itokawa collected over a wide range of solar phase angles (4 degrees-130 degrees) during the 2004 apparition (Thomas-Osip et al., this issue, hereafter Paper 1). Our photometric analyses indicate that Itokawa has a blocky surface with properties different from other, albeit larger, S-class asteroids studied using similar Hapke modeling analyses. Images from the Hayabusa spacecraft affirm the Hapke modeling results, demonstrating the ability of Hapke photometric modeling to predict a rocky asteroid surface correctly; this is the first time that a predicted rocky surface has been observed by a spacecraft. The single particle scattering functions are dominantly forward scattering, suggesting the surface material is composed primarily of clear particles whose scattering is dictated by the particle's surface as opposed to internal scatterers (more typical of S-class asteroids), while the opposition parameters indicate that the regolith may be more compact than most of the limited number of asteroids visited by spacecraft to date. The roughness properties, single particle scattering properties, and opposition surge characteristics are all indicative of a surface where multiple scattering does not play a major role in defining the photometric properties of the regolith.

In 2004, Asteroid 25143 Itokawa made its final close approach to the Earth prior to its encounter with the Japanese spacecraft Hayabusa. This apparition was superb with Itokawa reaching magnitude 12 (two magnitudes brighter than the 2001 apparition and the brightest since its discovery in 1998) and covering a large range of observable solar phase angles. An extensive visible and near-infrared observing campaign of Itokawa was undertaken at Las Campanas and Lowell Observatories to obtain full rotational coverage and cover the largest possible range of solar phase angles (4-129 degrees). Unresolved global color mapping over the complete light curve (best fit synodic period of 12.118 hr) shows no sign of rotational color variability with upper limits of a few percent across the full U-thru-K spectrum. These combined multi-wavelength (UBVRIJHK) rotational light curves allow for the concrete deconvolution of shape from albedo variation in the rotational models and as required for Hapke modeling presented in Paper II (Lederer et al., this issue), permits the removal of the rotational light curve effects from the solar phase curve. Furthermore, these derived solar phase curves can be fit with the IAU H,G magnitude system (Bowell et al., 1989) thus allowing the calculation of geometric albedos (p(v) = 0.23 +/- 0.02) as well as an estimate of the asteroid's elongated shape (a/b = 1.9 +/- 0.1) via the amplitude-phase relationtionship (Zappala et al., 1990). Results derived from the extensive ground-based campaigns are compared and contrasted with the much higher spatial resolution in situ measurements made by the Hayabusa spacecraft. The 'ground-truth' provided by the Hayabusa mission results shed light on the inferences that can begin to be made for the general asteroid population.

This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the Magellan-Baade 6.5 m telescope. MMTF is based on a 150 mm clear aperture Fabry-Perot (FP) etalon that operates in low orders and provides transmission bandpass and central wavelength adjustable from similar to 5 angstrom to similar to 15 angstrom and from similar to 5000 angstrom to over similar to 9200 angstrom, respectively. It is installed in the Inamori Magellan Areal Camera and Spectrograph and delivers an image quality of similar to 0.'' 5 over a field of view of 27' in diameter (monochromatic over similar to 10'). This versatile and easy-to-operate instrument has been used over the past three years for a wide variety of projects. This paper first reviews the basic principles of FP tunable filters, and then provides a detailed description of the hardware and software associated with MMTF and the techniques developed to observe with this instrument and reduce the data. The main lessons learned in the course of the commissioning and implementation of MMTF are highlighted next, before concluding with a brief outlook on the future of MMTF and of similar facilities which are soon coming on line.