ABSTRACT We present Hubble Space Telescope optical images, Keck-OSIRIS near-infrared (NIR) integral field spectroscopy data cubes and Keck-Near InfraRed Camera-2 (NIRC2) NIR images of nova V5668 Sgr from 2016 to 2019. The observations indicate enhanced emission at the polar caps and equatorial torus for low-ionization lines, and enhanced high-ionization emission lines only at the polar caps. The radial velocities are compatible with a homogeneous expansion velocity of v = 590 km s−1 and a system inclination angle of 24°. These values were used to estimate an expansion parallax distance of 1200 ± 400 pc. The NIRC2 data indicate the presence of dust in 2016 and 2017, but no dust emission could be detected in 2019. The observational data were used for assembling 3D photoionization models of the ejecta. The model results indicate that the central source has a temperature of 1.88 × 105 K and a luminosity of 1.6 × 1035 erg s−1 in August of 2017 (2.4 yr post eruption), and that the shell has a mass of 6.3 × 10−5 M⊙. The models also suggest anisotropy of the ionizing flux, possibly by the contribution from a luminous accretion disc.

In this work we investigated the longitudinal (zonal) variability of H2O and ammonia (NH3) hydrate ices on the surface of Charon through analysis of the 1.65 mu m and 2.21 mu m absorption features, respectively. Near-infrared spectra presented here were obtained between 2015-07-14 and 2015-08-30 UT with the OSIRIS integral field spectrograph on Keck I. Spectra centered on six different sub-observer longitudes were obtained through the Hbb (1.473-1.803 mu m) and Kbb (1.965-2.381 mu m) filters. Gaussian functions were fit to the aforementioned bands to obtain information on band center, band depth, full width at half maximum, and band area. The shift in the band center of the temperature-dependent 1.65 mu m feature was used to calculate the H2O ice temperature. The mean temperature of the ice on the observable portion of Charon's surface is 45 +/- 14 K and we report no statistically significant variations in temperature across the surface. We hypothesize that the crystalline and amorphous phases of water ice reached equilibrium over 3.5 Gyr ago, with thermal recrystallization balancing the effects of irradiation amorphization. We do not believe that cryovolcanism is necessary to explain the presence of crystalline water ice on the surface of Charon. Absorption from ammonia species is detected between 12 degrees and 290 degrees, in agreement with results from New Horizons. Ongoing diffusion of ammonia through the rocky mantle and upper layer of water ice is one possible mechanism for maintaining its presence in Charon's surface ice. Reduced Charon spectra corrected for telluric and solar absorption are available as supplementary online material. (C) 2016 Elsevier Inc. All rights reserved.

We present spatially resolved infrared spectra of V723 Cas (Nova Cassiopeia 1995) obtained over four years with the integral field spectrograph OSIRIS on Keck II. Also presented are one epoch of spatially unresolved spectra from the long slit spectrograph NIRSPEC on Keck II. The OSIRIS observations made use of the laser guide star adaptive optics facility that produced diffraction-limited spatial resolution of the strong coronal emission features in the nova ejecta. We remove the point-like continuum from V723 Cas data cubes to reveal details of the extended nebula and find that emission due to [Si VI] and [Ca VIII] has an equatorial ring structure with polar nodules-a strikingly different morphology than emission due to [Al IX], which appears as a prolate spheroid. The contrast in structure may indicate separate ejection events. Using the angular expansion and Doppler velocities observed over four epochs spaced at one year intervals, we determine the distance to V723 Cas to be 3.85(-0.21)(+0.23) kpc. We present the OSIRIS three-dimensional data here in many ways: as narrowband images, one-and two-dimensional spectra, and a volume rendering that reveals the true shape of the ejecta.

The Deep Impact encounter with 9P/Tempel 1, a Jupiter Family Comet (JFC), on UT 2005 July 04 was observed at high spectral resolution (lambda/Delta lambda approximate to 25,000) using the cross-dispersed near-infrared echelle spectrometer (NIRSPEC) at Keck-2. This permitted a simultaneous measure of individual line intensities for several parent molecules in addition to dust continuum emission. Column abundances are presented for H2O and C2H6 beginning 30 minutes prior to impact (T-30) and ending 50 minutes following impact (T+50), and for H2O and HCN front T+50 until T+96, in time steps of approximately six minutes post-impact.The ejecta composition was revealed by all abrupt increase in H2O and C2H6, near T+25. This showed C2H6/H2O to be higher than its pre-impact value by a factor 2.4 +/- 0.5, while HCN/H2O was unchanged within the uncertainty of the measurements. The mixing ratios for C2H6 and HCN ill the ejecta agree with those found in the majority of Oort cloud comets, perhaps indicating a common region of formation. This stands in contrast with the recently observed split JFC 73P/Schwassmann-Wachmann 3 and the disintegrated Oort cloud comet D/1999 S4 (LINEAR), both of which were depleted in most; organic volatiles, but not HCN.The expanding dust plume was tracked through the 3.5-mu m spectral continuum and through 2-mu m images acquired with the slit-viewing camera (SCAM). These showed a monotonic increase in continuum intensity following impact. The relatively sudden appearance of the volatile ejecta signature is attributed to heating of icy grains (perhaps to a threshold temperature) that were decreasingly shadowed by intervening (sunward) particles.

Nova V2362 Cygni has undergone a number of very unusual changes. Ground-based spectroscopy initially revealed a normal sequence of events: the object faded and its near-infrared emission lines gradually shifted to higher excitation conditions until about day 100 when the optical fading reversed and the object slowly brightened. This was accompanied by a rise in the Swift X-ray telescope flux and a sudden shift in excitation of the visible and IR spectrum back to low levels. The new lower excitation spectrum revealed broad line widths and many P-Cygni profiles, all indicative of the ejection of a second shell. Eventually, dust formed, the X-ray brightness—apparently unaffected by dust formation—peaked and then declined, and the object faded at all wavelengths. The Spitzer dust spectra revealed a number of solid-state emission features that, at this time, are not identified.

We report optical photometry and optical through mid-infrared spectroscopy of the classical nova V1186 Sco. This slowly developing nova had a complex light curve with multiple secondary peaks similar to those seen in PW Vul. The time to decline 2 mag, t2, was 20 days, but the erratic nature of the light curve makes determination of intrinsic properties based on the decline time (e.g., luminosity) problematic, and the often-cited relationship of maximum magnitude versus the rate of decay of the light curve of Della Valle & Livio fails to yield a plausible distance. Spectra covering 0.35-35 μm were obtained in two separate epochs during the first year of outburst. The first set of spectra, taken about 2 months after visible maximum, are typical of a CO-type nova with narrow-line emission from H I, Fe II, O I, and He I. Later data, obtained between 260 and 380 days after maximum, reveal an emerging nebular spectrum. Spitzer spectra show weakening hydrogen recombination emission with the emergence of [Ne II] (12.81 μm) as the strongest line. Strong emission from [Ne III] (15.56 μm) is also detected. Photoionization models with low effective temperature sources and only marginal neon enhancement (Ne ∼ 1.3 Ne⊙) are consistent with these IR fine-structure neon lines indicating that V1186 Sco did not occur on a ONeMg white dwarf. In contrast, the slow and erratic light-curve evolution, spectral development, and photoionization analysis of the ejecta imply that the outburst occurred on a low-mass CO white dwarf. We note that this is the first time strong [Ne II] lines have been detected so early in the outburst of a CO nova and suggest that the presence of mid-infrared neon lines is not directly indicative of a ONeMg nova event.

We report on an unprecedented infrared time series of spectra of V1187 Sco, a very fast ONeMg nova. The observations covered a 56 day period (2004 August 6-September 30) starting 2 days after the nova's peak brightness. Time evolution of the spectra revealed changing line strengths and profiles on timescales of less than a day to weeks as the nova evolved from early postmaximum to early coronal phases. When our ground-based optical and Spitzer Space Telescope data were combined, the wavelength coverage of 0.38-36 μm allowed an accurate spectral energy distribution to be derived when it was about 6 weeks after outburst. Developing double structure in the He I lines showed them changing from narrow to broad in only a few days. Using the O I lines in combination with the optical spectra, we derived a reddening of E(B - V) = 1.56 ± 0.08 and a distance of 4.9 ± 0.5 kpc. Modeling of the ejected material strongly suggested that it was geometrically thick with ΔR/R = 0.8-0.9 (more of a wind than a shell) and a low filling factor of order a few percent. The line shapes were consistent with a cylindrical jet, bipolar, or spherical Hubble flow expansion with a maximum speed of about -3000 km s-1. The central peak appeared to be more associated with the spherical component, while the two peaks (especially in Hβ) suggested a ring with either a lower velocity component or with its axis inclined to the line of sight.

We quantified eight parent volatiles (H 2 O, C 2 H 6 , HCN, CO, CH 3 OH, H 2 CO, C 2 H 2 , and CH 4 ) in the Jupiter-family comet Tempel 1 using high-dispersion infrared spectroscopy in the wavelength range 2.8 to 5.0 micrometers. The abundance ratio for ethane was significantly higher after impact, whereas those for methanol and hydrogen cyanide were unchanged. The abundance ratios in the ejecta are similar to those for most Oort cloud comets, but methanol and acetylene are lower in Tempel 1 by a factor of about 2. These results suggest that the volatile ices in Tempel 1 and in most Oort cloud comets originated in a common region of the protoplanetary disk.

We report the results of a 20 year campaign to monitor the infrared (IR) spectral energy distribution ( SED) of the "born again'' star FG Sge, which is embedded in an old planetary nebula. The IR data show that the central star apparently reestablished an essentially steady state post - asymptotic giant branch (AGB) type wind in late 1992. Since then, the visual light curve has shown irregular large amplitude variations on timescales of 200 - 400 days, while the IR SED has maintained a constant luminosity. The IR SED has been dominated by thermal emission from carbon dust at a temperature of similar or equal to 1000 K for nearly 10 years. The thermal emission is primarily from grains forming in the 1000 K condensation zone at the base of the outflow. The wind appears to be optically thick in the visual, and the central engine may be undergoing episodes of pulsational activity that cause the visual optical depth of the wind to vary. The central engine appears to be cooling steadily at constant luminosity. We estimate the mass-loss rate of the FG Sge wind to be between 2.3 x 10(-5) and 1.2 x 10(-4) M-. yr(-1) as would be expected for a star rejoining the tip of the AGB.