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In late 2003, the young eruptive variable star V1647 Orionis optically brightened by over 5 magnitudes, stayed bright for around 26 months, and then decline to its pre-outburst level. In August 2008 the star was reported to have unexpectedly brightened yet again and we herein present the first detailed observations of this new outburst. Photometrically, the star is now as bright as it ever was following the 2003 eruption. Spectroscopically, a pronounced P Cygni profile is again seen in Halpha with an absorption trough extending to -700 km/s. In the near-infrared, the spectrum now possesses very weak CO overtone bandhead absorption in contrast to the strong bandhead emission seen soon after the 2003 event. Water vapor absorption is also much stronger than previously seen. We discuss the current outburst below and relate it to the earlier event., 6 pages, 3 figures

We report 8- to 13-micron spectral observations of Neptune and Uranus from the NASA Infrared Telescope Facility spanning more than a decade. The spectroscopic data indicate a steady increase in Neptune's mean atmospheric 12-micron ethane emission from 1985 to 2003, followed by a slight decrease in 2004. The simplest explanation for the intensity variation is an increase in stratospheric effective temperature from 155 +/- 3 K in 1985 to 176 +/- 3 K in 2003 (an average rate of 1.2 K/year), and subsequent decrease to 165 +/- 3 K in 2004. We also detected variation of the overall spectral structure of the ethane band, specifically an apparent absorption structure in the central portion of the band; this structure arises from coarse spectral sampling coupled with a non-uniform response function within the detector elements. We also report a probable direct detection of ethane emission on Uranus. The deduced peak mole fraction is approximately an order of magnitude higher than previous upper limits for Uranus. The model fit suggests an effective temperature of 114 +/- 3 K for the globally-averaged stratosphere of Uranus, which is consistent with recent measurements indicative of seasonal variation., Accepted for publication in ApJ. 16 pages, 10 figures, 2 tables

STIS white-light coronagraphic imaging has been carried out for 14 nearby, lightly reddened Herbig Ae stars, providingdataontheenvironmentsanddisksassociatedwiththesestars.Nodisksaredetectedinourdatawhenthe Herbig Ae starisaccompaniedbya stellarcompanion atr � 2 00 .Wefindthattheopticalvisibilityofprotoplanetary disks associated with Herbig Ae stars at r � 50 70 AU from the star is correlated with the strength of the mid-IR PAH features, particularly 6.2 � m. These features, like the FUV fluorescent H2 emission, trace the presence of material sufficiently far above the disk midplane that it is directly illuminated by the star’s FUV radiation. In contrast, measures of the bulk properties of the disk, including ongoing accretion activity, mass, and the submillimeter slope of the SED, do not correlate with the surface brightness of the optical nebulosity. Modelers have interpreted the appearance of the IR SED and the presence of emission from warm silicate grains at 10 � ma s a measure of geometrical shadowing by material in the disk near the dust sublimation radius of 0.5 AU. Geometrical shadowing sufficient to render a disk dark to distances as large as 500 AU from a star would require that the star be optically visible only if viewed essentially pole-on, in disagreement with our program star system inclinations. Rather than invoking shadowing to account for the optically dark disks, the correlation of the STIS detections with PAHemissionfeaturessuggestsacorrelationwithdiskflaringandananticorrelationwiththedegreeofdustsettling toward the midplane. If this correlation continues to lower levels, the STIS data suggest that improvements in coronagraph performance that suppress the residual scattered and diffracted stellar light by an additional factor of � 10 should render the majority of disks associated with nearby Herbig Ae stars detectable. Subject headingg infrared: stars — ISM: Herbig-Haro objects — ISM: jets and outflows — stars: pre–main-sequence

We present new observations of the FUV (1100-2200 Angstrom) radiation field and the near- to mid-IR (3--13.5 micron) spectral energy distribution (SED) of a sample of T Tauri stars selected on the basis of bright molecular disks (GM Aur, DM Tau, LkCa15). In each source we find evidence for Ly alpha induced H2 fluorescence and an additional source of FUV continuum emission below 1700 Angstroms. Comparison of the FUV spectra to a model of H2 excitation suggests that the strong continuum emission is due to electron impact excitation of H2. The ultimate source of this excitation is likely X-ray irradiation which creates hot photo-electrons mixed in the molecular layer. Analysis of the SED of each object finds the presence of inner disk gaps with sizes of a few AU in each of these young (~1 Myr) stellar systems. We propose that the presence of strong H2 continuum emission and inner disk clearing are related by the increased penetration power of high energy photons in gas rich regions with low grain opacity., 5 pages, 3 figures, accepted by ApJ Letters

We report 3 - 13 micron spectroscopy of 4 comets observed between August 2002 and February 2003: C/2002 O4 (Honig) on August 1, 2002, C/2002 V1 (NEAT) on Jan. 9 and 10, 2003, C/2002 X5 (Kudo-Fujikawa) on Jan. 9 and 10, 2003, and C/2002 Y1 (Juels-Holvorcem) on Feb. 20, 2003. In addition, we include data obtained much earlier on 69P/Taylor (February 9, 1998) but not previously published. For Comets Taylor, Honig, NEAT, and Kudo-Fujikawa, the silicate emission band was detected, being approximately 23%, 12%, 15%, and 10%, respectively, above the continuum. The data for Comet Juels-Holvorcem were of insufficient quality to detect the presence of a silicate band of comparable strength to the other three objects, and we place an upper limit of 24% on this feature. The silicate features in both NEAT and Kudo-Fujikawa contained structure indicating the presence of crystalline material. Combining these data with those of other comets, we confirm the correlation between silicate band strength and grain temperature of Gehrz & Ney (1992) and Williams et al. (1997) for dynamically new and long period comets, but the majority of Jupiter family objects may deviate from this relation. The limited data available on Jupiter family objects suggest that they may have silicate bands that are slightly different from the former objects. Finally, when compared to the silicate emission bands observed in pre-main sequence stars, the dynamically new and long period comets most closely resemble the more evolved stellar systems, while the limited data (in quantity and quality) on Jupiter family objects seem to suggest that these have spectra more like the less-evolved stars., 45 pages, 12 figures

We report on the results of a number of infrared spectra (0.8-2.5, 2.1-4.6, and 3-14 microns) of V838 Monocerotis, taken from a short time after discovery in 2002 January to about 14 months later, in early 2003. The spectrum evolved dramatically, changing from a quasi-photospheric stellar spectrum with weak atomic emission lines (some with P Cygni profiles) to one showing a wide range of deep absorption features indicative of a cool, extended atmosphere with a circumstellar dust shell. The early spectra showed lines of s-process elements, such as Sr II and Ba I. The later spectra showed absorption by gaseous H2O, CO, AlO, TiO, SiO, SO2, OH, VO, and SH, as well as a complex of emission near 10 microns reminiscent of silicate emission, with a central absorbing feature at 10:3 microns. Thus, V838 Mon appears to be oxygen-rich. A simple, spherically symmetric model of the system involving a central star with a two-component expanding circumstellar shell is presented that is able to explain the major molecular features and spectral energy distribution in the object's late stages. The derived shell mass and distance are 0.04 M(circle dot solar) and 9.2 kpc, respectively.

The debris disks surrounding the pre-main sequence stars HD 31648 and HD 163296 were observed spectroscopically between 3 and 14 microns. Both possess a silicate emission feature at 10 microns which resembles that of the star beta Pictoris and those observed in solar system comets. The structure of the band is consistent with a mixture of olivine and pyroxene material, plus an underlying continuum of unspecified origin. The similarity in both size and structure of the silicate band suggests that the material in these systems had a processing history similar to that in our own solar system prior to the time that the grains were incorporated into comets.

We present intermediate-resolution (λ/Δλ ≈ 60) spectra of 21 ultracompact H II regions in the spectral range from 3 to 13 μm. The 9.7 μm silicate feature is seen in absorption, and the 12.8 μm [Ne II] fine structure line is seen in emission toward most of the observed nebulae. The strengths of both features vary enormously from nebula to nebula, suggesting large variations in the column densities of both Ne II and silicates toward these objects. Near-IR features attributed to polycyclic aromatic hydrocarbons (PAHs) are detected in six of the sources. Spherically symmetric dust shell models were calculated to obtain the best fits to those nebulae for which distances are known, and spectral energy distributions are available in the range of 1 mm to 1 μm. The models are used to infer properties of the dust cocoon such as the distribution of density and temperature with radius, shell thickness, outer shell radius, and dust abundances. Our results are consistent with previous models that predict large dust cocoons with central cavities, sharp temperature gradients, and approximately constant density in the outer regions.

Redshifted absorption profiles that resemble the high-velocity circumstellar gas features in the spectrum of β Pictoris have been detected in IUE data for the 10 Myr old Herbig Be star, HD 100546, on 1995 March 7. In addition to Mg II, Si II, and other refractory species similar to those seen in β Pic, the HD 100546 spectra are rich in accreting gas profiles from neutral atomic gas, including C I and O I, as well as mildly refractory species such as Zn II and S II. The presence of accreting gas profiles, including neutral atomic gas, is consistent with detection of comae of star-grazing bodies potentially resembling either comets or asteroids. Overall, the IUE data for HD 100546 are consistent with the planetesimals in this system being more volatile-rich and magnesium-rich than similar bodies in the β Pic system.

We present near- and mid-infrared (MIR) interferometric observations made with the Keck Interferometer Nuller and near-contemporaneous spectro-photometry from the infrared telescope facilities (IRTFs) of 11 well-known young stellar objects, several of which were observed for the first time in these spectral and spatial resolution regimes. With au-level spatial resolution, we first establish characteristic sizes of the infrared emission using a simple geometrical model consisting of a hot inner rim and MIR disk emission. We find a high degree of correlation between the stellar luminosity and the MIR disk sizes after using near-infrared data to remove the contribution from the inner rim. We then use a semi-analytical physical model to also find that the very widely used "star + inner dust rim + flared disk" class of models strongly fails to reproduce the spectral energy distribution (SED) and spatially resolved MIR data simultaneously; specifically a more compact source of MIR emission is required than results from the standard flared disk model. We explore the viability of a modification to the model whereby a second dust rim containing smaller dust grains is added, and find that the 2-rim model leads to significantly improved fits in most cases. This complexity is largely missed when carrying out SED modeling alone, although detailed silicate feature fitting by McClure et al. recently came to a similar conclusion. As has been suggested recently by Menu et al., the difficulty in predicting MIR sizes from the SED alone might hint at "transition disk"-like gaps in the inner au; however, the relatively high correlation found in our MIR disk size versus stellar luminosity relation favors layered disk morphologies and points to missing disk model ingredients instead.

Previous studies of the classical T Tauri star AA Tau have interpreted the UX-Orionis-like photo-polarimetric variability as being due to a warp in the inner disk caused by an inclined stellar magnetic dipole field. We test that these effects are macroscopically observable in the inclination and alignment of the disk. We use Hubble Space Telescope (HST)/STIS coronagraphic imagery to measure the V magnitude of the star for both STIS coronagraphic observations, compare these data with optical photometry in the literature, and find that, unlike other classical T Tauri stars observed in the same HST program, the disk is most robustly detected in scattered light at stellar optical minimum light.We measure the outer disk radius, 1 inch.15 plus-minus 0 inch.10, major-axis position angle, and disk inclination and find that the inner disk, as reported in the literature, is both misinclined and misaligned with respect to the outer disk. AA Tau drives a faint jet, detected in both STIS observations and in follow-on Goddard Fabry-Perot imagery, which is also misaligned with respect to the projection of the outer disk minor axis and is poorly collimated near the star, but which can be traced 21 inches from the star in data from 2005. The measured outer disk inclination, 71deg plus-minus 1deg, is out of the range of inclinations suggested for stars with UX-Orionis-like variability when no grain growth has occurred in the disk. The faintness of the disk, small disk size, and detection of the star despite the high inclination all indicate that the dust disk must have experienced grain growth and settling toward the disk midplane, which we verify by comparing the observed disk with model imagery from the literature.

We have analyzed the existing spectra of seven comets which show an emission feature at 7.8-13 micrometers. Most have been converted to a common calibration, taking into account the SiO feature in late-type standard stars. The spectra are compared with spectra of the Trapezium, interplanetary dust particles (IDPs), laboratory mineral samples, and small particle emission models. The emission spectra show a variety of shapes; there is no unique 'cometary silicate'. A peak at 11.20-11.25 micrometers, indicative of small crystalline olivine particles, is seen in only three comets of this sample, P/Halley, Bradfield 1987 XXIX, and Levy 1990 XX. The widths of the emission features range from 2.6 to 4.1 micrometers (FWHM). To explain the differing widths and the broad 9.8 micrometers maximum, glassy silicate particles, including both pyroxene and olivine compositions, are the most plausible candidates. Calculations of emission models confirm that small grains of glassy silicate well mixed with carbonaceous material are plausible cometary constituents. No single class of chondritic aggregate IDPs exhibits spectra closely matching the comet spectra. A mixture of IDP spectra, particularly the glass-rich aggregates, approximately matches the spectra of comets P/Halley, Levy, and Bradfield 1987 XXIX. Yet, if comets are simply a mix of IDP types, it is puzzling that the classes of IDPs are so distinct. None of the comet spectra match the spectrum of the Trapezium. Thus, the mineralogy of the cometary silicates is not the same as that of the interstellar medium. The presence of a component of crystalline silicates in comets may be evidence of mixing between high- and low-temperature regions in the solar nebula.

We have obtained intermediate-resolution (R≃50) infrared (2.6-13.5 μm) spectra of the particles in the circumstellar disk of β Pic. The silicate dust feature near 10 μm is broader and contains more structure than interstellar and most circumstellar emission features. The silicate feature in β Pic is remarkably similar to those in comets Halley, Bradfield 1987s, and Levy 1990 XX which have emission features characteristic of crystalline silicates. This result supports the inference based on IRAS results that cometary bodies resupply the grains in the β Pic disk. Detailed models of the dust disk and grains are used to derive plausible disk temperature and density gradients

Measurements of the G333.6-0.2 H II region which include the first detection of the N II 122 micron forbidden line in an astronomical force and the first measurement of the N II 205 micron forbidden line in a discrete source are presented. Also considered are fine structure lines of forbidden S III, forbidden Fe III, forbidden Si II, forbidden Ne III, forbidden O III, forbidden N III, forbidden O I, and forbidden C II from 19 to 206 microns. It is concluded that the N II 122 and 205 microns forbidden line pair in a discrete astronomical source was detected for the first time. The emission in transitions is produced largely by low-ioninzation, low-density material not easily probed by other lines. Other FIR line pairs generally originate in higher density regions closer to the exciting force.

Using the new Aerospace spectrometer on the Kuiper Airborne Observatory, we have obtained observations of the molecular shocks associated with OMC-1. Unexpectedly these observations reveal (b = 1-0) emission from CO at 4.6 microns superposed on a strong continuum. Our observations strongly suggest that both the emission feature and the continuum are produced in molecular shocks. Since the (v = 1-0) band of CO is only excited in high-velocity shocks, we may be observing for the first time the primary driving mechanism in these regions. Even if these features are produced by scattering, the characteristics will provide new constraints on the conditions in and the geometry of the shock regions.

Infrared spectroscopy of Nova Herculis 1991 between 8 and 13 μm 80 days after maximum revealed a large featureless infrared excess that was caused by a shell of optically thin silicate dust. The lack of an identifiable continuum underlying the silicate feature suggests that the grain radii were smaller than about 0.8 μm. The absolute visual magnitude at maximum M v (max) was -9.4, the extinction A v was 1.7 mag, and the distance d was 3.4 kpc

Spectrophotometry in the range 2.1-4.0 microns is presented for the Seyfert galaxies NGC 1068, NGC 4151 and Mrk 231 and the quasar 3C 273, together with broadband and narrowband observations of the Seyfert galaxies in the range 8-13 microns. The spectra of NGC 1068 and NGC 4151 are found to contain a significant component due to starlight, especially at shorter wavelengths. The nonstellar component in NGC 1068 is observed to fall off rapidly at wavelengths shorter than 4 microns, consistent with the interpretation of the excess beyond 5 microns as thermal reradiation by dust. Observations confirm the variability of NGC 4151, and indicate the presence of two components of the flux other than starlight: a nonthermal variable component predominant at shorter wavelengths and a constant, probably thermal component at wavelengths greater than 3 microns. Mrk 231 and 3C 273 exhibit no discernable stellar component and were not observed to vary by more than 10%. Evidence is obtained for a broad minimum in the 8 to 13 micron spectrum of Mrk 231, as well as possible structure between rest wavelengths of 2.8 and 2.9 microns, and the spectrum is not a power law. The spectrum of 3C 273 is consistent with a power law from 1.2 to 10 microns, with small but significant deviations.

The submillimeter (157-micron) forbidden line emission from the M17 complex has been mapped. The forbidden line emission extends over at least 1/4 deg in the sky. The regions emitting the C II radio recombination lines contribute only in a minor way to the total 157-micron flux. The total forbidden line luminosity of M17 exceeds 2,000 solar luminosities.

Spectrophotometry of HM Sge from 2 to 13 microns is presented along with 2 to 4-micron spectrophotometry of V1016 Cyg. From 2.5 to 8 microns, the spectrum of HM Sge can be represented by a 950-K blackbody, and a strong silicate emission feature is seen from 8 to 13 microns. Both HM Sge and V1016 Cyg show evidence of CO absorption at 2.3 microns. It is suggested that the infrared radiation from these objects arises from a combination of emission by optically thin dust and by the reddened photosphere of a cool star.

Several possible analogs of cosmic dust have been produced by a variety of techniques. Extinction and emission spectra of these grain samples reveal that hydrated silicates, in particular those which are Mg-rich, produce infrared spectra that bear strong resemblances to the spectra of a variety of astronomical dust grains ranging from those found within the solar system to those found in dense, cold, molecular clouds. An identification of hydrated silicates as the origin of the 6.0 and 6.8 micron features is proposed as part of a model which is consistent with all the spectra available to date on both cosmic dust and the laboratory samples studied. 34 references.

Airborne and ground-based observations show that OH 26.5+0.6 has strong 10 micrometers and weak 18 micrometers silicate absorptions superposed on an overall energy distribution much like a blackbody. The flux level, color temperature, and depth of the 10 micrometers absorption have varied during two years of observations. A model of the source as a late-type variable star that has ejected an optically thick dust shell is suggested; the mass-loss rate implied is greater than about 0.00001 solar masses per year. The fact that significant flux from the source is observed between 4 and 7 micrometers is evidence that oxygen-rich dust has significant opacity in that wavelength range.

Portions of the nebula NGC 2024 were mapped in the 157 micron (C II) line. Results show the presence of a compact component centered on the radio-recombination line regions and a more extended nebulosity. It is found that the central component emits 157 micron line and continuum fluxes at a level of 4 x 10 to the -16th W/sq cm and 5 x 10 to the -16th W/sq cm (micron), respectively. The continuum emission drops off more rapidly with distance from the peak, although line emission is approximately 30% of the peak value at a distance 18 min to the SE of the peak. In addition, related observations were carried out on M42.

The paper deals with spectrophotometric observations covering the essentially complete wavelength interval between 1.2 and 30.0 microns. The observations confirm the identification of the C3 band at 5.2 microns. They show that if SiC2 is present, the SiC1 absorption band at 5.7 microns would be obscured by C3 at a 1% spectral resolution. Silicon carbide emission at 11.5 microns exists simultaneously with C3 absorption at 5.2 microns, requiring a contribution of both species to the violet opacity of Y CVn.

Observations of the Kleinmann-Low Nebula in Orion detected the J = 17-J = 16 transition of CO at 153 microns and at a flux level of 7 x 10 to the -17th W/sq cm. The total mass of hot (not less than about 750 K) carbon monoxide in the nebula is estimated at 8 x 10 to the 30th g, and the total hydrogen mass at this temperature is assessed to be about 1.5 solar masses. A CO column density of about 4 x 10 to the 17th per sq cm is derived for the region, which agrees with those predictions made by Storey et al. (1981), and an apparent deficit of oxygen in the nebula is discussed.

Spectrophotometric observations of Eta Car between 4.5 and 7.5 microns show a featureless thermal-like spectrum with no fine-structure lines or broad emission or absorption features. The color temperature of the spectrum is approximately 375 K. High spatial resolution maps at 3.5, 4.8, and 10 microns obtained from the ground are used to discuss the dust distribution and temperature structure, and to present a model for general source morphology. The upper limit to the brightness of the forbidden Ar II fine-structure emission line at 6.98 microns is less than 7 x 10 to the -16th W/sq cm, which still allows for a significant overabundance of argon and is consistent with the evolved nature of the source.

Spectrophotometric observations of NGC 7027 from 2.1 to 4.1 $mu$ with a resolution $delta$lambda/lambdaapprox.0.015 are reported. The spectrum is rich in features, including three hydrogen recombination lines and several unidentified features. The 2-$mu$ continuum level and the hydrogen recombination- line fluxes agree well with predictions based on the observed radio and H$beta$ fluxes.

The first observation of a fine-structure transition in NGC 7027 at wavelengths greater than 30 microns is reported. The flux in the 63.2-micron line is found to be approximately 10 to the -16th W/sq cm. It is noted that if NGC 7027 lies at 1 kpc, this corresponds to a luminosity, in the line, approximately 30 times greater than the solar luminosity. The flux of the 88.35-micron line is less than 10 to the -17th W/sq cm, and the upper limit to the line flux at 51.8 microns is found to be 10 to the -16th W/sq cm. These upper limits imply an electron density that is less than 1.6 x 10 to the 5th/cu cm. It is noted that the continuum measurements obtained support a dust temperature of 90 K with an emissivity approximately equal to the reciprocal of the square of the wavelength. The data exclude grain materials whose wavelength-dependent emissivity (the reciprocal of the wavelength raised to nth power) requires n to be outside the range between 1.6 and 2, unless the temperature varies drastically across the dust cloud

Observations of the complex Sgr A W(N) with a 28-arcsec beam and 1.5% spectral resolution are reported. Neither unidentified absorption features at 6.0 and 6.8 microns nor emission features at 6.2 and 7.7 microns were detected. The absence of the absorption features demonstrates that they are not characteristic of general interstellar extinction. The absence of emission features suggests that there is considerable distance between the ionized gas and the molecular clouds. The absence of 6.2- and 7.7-micron emission features also suggests that a feature previously seen at 3.3-3.4 microns is an absorption at 3.4 microns, and this absorption is apparently characteristic of interstellar extinction. The strength of the forbidden Ar II emission indicates an overabundance of argon. CO absorption seen at 4.67 microns indicates that saturation effects are not large, and there is evidently a large velocity dispersion in the line of sight to the infrared sources.

Spectrophotometric observations from 4 to 8 microns of the compact H II regions W51-IRS 2 and K3-50 are reported. Two broad absorption features at approximately 6.0 and 6.8 microns are observed in the spectra of W51-IRS 2, and the 6.0-micron feature is seen in K3-50. These features may be due to absorption by silicate grains. A more speculative identification is absorption by hydrocarbon molecules. The continuum flux from 2 to 13 microns is broader than emission from a single-temperature blackbody; this suggests a distribution of dust temperatures within the H II regions. Failure to detect hydrogen Pfund-alpha in W51-IRS 2 indicates significant 7.5-micron extinction. Upper limits are placed on the abundance of Ar(+).

Observations have been made of two quadrupole purely rotational transitions of molecular hydrogen, the 0-0 S(7) and S(5) lines, and of several previously unobserved vibration-rotation hydrogen lines in the Orion molecular cloud. The line ratios indicate a 2.1-micron extinction of about 2 mag. A comparison of the populations of three vibrational levels shows a distribution of excitation temperatures between 1000 and 3000 K. These values are consistent with the theory that hydrogen is thermally excited in shock-heated gas which cools after passage of the shock front. The total luminosity of the hot molecular hydrogen is 200 plus or minus 80 solar luminosity, and the mass of the emitting gas is of the order 0.05 solar mass. The mass and cooling times of the hot hydrogen indicate that at least 10 solar mass of the material has been heated over the lifetime of the outflow.

Observation spectroscopique entre 5,25 et 12,6 μm de l'observatoire Kuiper, environ 60 jours apres l'eruption initiale et 25 jours avant le maximum lumineux

We present the first detection of the (C II) fine-structure emission line at a wavelength of 157 ..mu..m. The (C II) line strengths are 7.1 x 10/sup -16/ and 1.0 x 10/sup -15/W cm/sup -2/, respectively, in NGC 2024 and M42. The line-to-continuum ratio is higher in NGC 2024 where the continuum is 7.0 x 10/sup -16/ W cm/sup -2/ ..mu..m/sup -1/, in contrast to M42 where it assumes a value of 2.6 x 10/sup -15/W cm/sup -2/ ..mu..m/sup -1/. The respective luminosities in the line are approx.50 and 80 L/sub sun/. The observations were obtained with a stressed Ge:Ga photoconductor.

Infrared spectrophotometric observations (2 to 24 microns) are reported for CRL 2688, an IR source in Cygnus associated with twin symmetric reflection nebulae. The entire spectrum from 3 to 24 microns is shown to be a generally featureless continuum and to be too broad to be fit by a single blackbody. No evidence is found for ice absorption near 3.1 microns, and the data suggest a possible emission feature near 3.3 microns.

Spectrophotometric observations from 2 to 4 microns and from 8 to 13 microns of several infrared sources associated with molecular clouds are reported. Narrow absorption features at 3.08 microns, attributed to interstellar ices, appear in all sources with a molecular cloud in the intervening line of sight. All sources showing ice absorptions also show broad absorption features, attributed to cold silicates, from 8 to 13 microns. The observed ice absorption profiles are all quite similar; however, they do not fit in detail Mie theory predictions of extinction for pure H2O or NH3 ices. The ratio of ice-to-silicate optical depths is found to vary, with most sources showing a ratio in the range 0.1-0.4. The ratio of visual extinction to ice absorption is found to increase rapidly from inside to outside the molecular cloud in NGC 2024.