Variation of the 3-μm absorption feature on Mars: Observations over eastern Valles Marineris by the Mariner 6 infrared spectrometer

The near-infrared spectrum of many sources associated with molecular clouds shows a broad absorption feature at 3.08 μm (e.g. Merrill et al., 1976; Harris et al., 1978). This feature has usually been attributed to absorption by H2O ice frozen on grains, but it has been impossible to satisfactorily reproduce the observed band shape (Merrill et al., 1976; Mukai et al., 1978). We have been able to obtain a complete fit of this absorption feature in the laboratory using very low temperature mixtures of H2O with other polar molecules. The preparation of these interstellar dust grain-mantle analogs has been described elsewhere (Greenberg, 1979; Hagen et al., 1979). They are prepared by allowing a gas mixture of simple molecules (e.g. CO, H2O, NH3, CH4 etc.) to condense on a low temperature (10 K) substrate. This frozen mixture can be heated and recooled. The samples are analyzed with an infrared spectrometer.

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Mid-IR spectra of the M-type Mira variable R Tri observed with the Spitzer IRS

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa322 ◽

2020 ◽

Vol 493 (1) ◽

pp. 807-814

Author(s):

Dana K Baylis-Aguirre ◽

M J Creech-Eakman ◽

Tina Güth

Keyword(s):

Ir Spectra ◽

Emission Feature ◽

Absorption Feature ◽

Cool Temperature ◽

Circumstellar Envelopes ◽

Mira Variables ◽

Mira Variable ◽

Molecular Lines ◽

Infrared Spectrometer ◽

Vibrational Bands

ABSTRACT We present analysis of mid-infrared (IR) spectra of the oxygen-rich Mira variable R Tri. The data were taken with the Spitzer Infrared Spectrometer (IRS) as part of a study tracking how Mira variables’ regular pulsations affect circumstellar envelopes. We detected strong emission lines at 13.87, 16.18, and 17.6 $\hbox{$\mu $m}$, and one strong absorption feature at 14.98 $\hbox{$\mu $m}$. The emission features at 13.87 and 16.18 $\hbox{$\mu $m}$ are excited vibrational bands of CO2, while the absorption feature is the fundamental ν2 band. The 17.6 $\hbox{$\mu $m}$ emission feature has a completely different character than the molecular lines and we report its identification as Fe i fluorescence. We used a two-slab model with the radiative transfer code radex to model the CO2 Q-branch bandheads. Our results indicate a slab of gas with T∼600 K located at ∼3–4 R*. The cool temperature discrepancy with the radius provides observational evidence for the previously theoretical ‘refrigeration zone’.

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The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Science ◽

10.1126/science.aav7432 ◽

2019 ◽

pp. eaav7432 ◽

Cited By ~ 33

Author(s):

K. Kitazato ◽

R. E. Milliken ◽

T. Iwata ◽

M. Abe ◽

M. Ohtake ◽

...

Keyword(s):

Near Infrared ◽

Surface Composition ◽

Parent Body ◽

Absorption Feature ◽

Direct Measurements ◽

Band Position ◽

Infrared Spectrometer ◽

Sample Return Mission ◽

Near Infrared Spectrometer ◽

Rubble Pile

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is thought to be a primitive carbonaceous object. We report reflectance spectra of Ryugu’s surface acquired with the Near Infrared Spectrometer (NIRS3) on Hayabusa2, to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 μm was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object, generated from impact fragments of an undifferentiated aqueously altered parent body.

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Relationships Between Color & Morphology on Bennu

10.5194/epsc2020-481 ◽

2020 ◽

Author(s):

Daniella DellaGiustina ◽

Keyword(s):

Principal Component ◽

Parent Body ◽

Space Science ◽

Absorption Feature ◽

Space Weathering ◽

Band Ratio ◽

Average Spectrum ◽

Wide Range ◽

Infrared Spectrometer ◽

High Reflectance

Abstract In September 2019, the OSIRIS-REx Camera Suite (OCAMS; Rizk et al., 2018) globally mapped asteroid (101955) Bennu in four broadband filters (b&#8242;, v, w, x) covering 0.44 to 0.89 microns. The multispectral images show complex relationships between color and morphology on Bennu&#8217;s surface. These data indicate that Bennu&#8217;s color has been influenced by primordial heterogeneity and space weathering. Introduction To evaluate relationships between color and morphology on Bennu, we radiometrically and photometrically corrected OCAMS images acquired by the MapCam instrument (Golish et al., 2020a, Golish et al., 2020b). Calibrated images were subsequently mosaicked to develop band-ratio and principal component analysis (PCA) maps. To establish statistically meaningful trends between color, reflectance, and morphological features, we mapped ~1600 boulders and ~700 craters, and extracted their average MapCam color indices. Bennu&#8217;s global average spectrum is blue (&#8211;1% per 0.1 &#956;m) in MapCam data (0.44 to 0.89 &#956;m), but spectral slopes can vary from blue (negative) to red (positive) at the meter scale. The diverse color and reflectance of boulders suggests primordial heterogeneity inherited from Bennu&#8217;s parent body and exogenic impactors (DellaGiustina and Kaplan et al., accepted). Spectral changes in craters as a function of radius indicate that color may also be influenced by space weathering on Bennu. &#160; Boulders On the basis of reflectance and color, we categorized Bennu&#8217;s boulders into four types: 1) High-reflectance boulders (>4.9% normal albedo) are brighter than units having the average color of Bennu, texturally smooth, exhibit angular morphology, and have blue spectral slopes across the MapCam v to x bands. 2) Dark boulders (&#8804;4.9% normal albedo) are subangular and have rougher, more undulating surface textures compared to the bright boulders. They encompass a wide range of sizes and include the largest boulders on the asteroid (25 to 100 m in diameter). 3) Boulders with very high reflectance (up to 0.26; ~1% in number) show evidence of an absorption at 1 &#956;m (downturn in the x band). These boulders were spectroscopically identified to contain pyroxene using data acquired by the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS; Reuter et al., 2018). 4) About 2% of boulders surveyed have an absorption feature that is detectable above the radiometric uncertainty of OCAMS at 0.7 &#956;m (absorption depth of 2 to 10%). This absorption has been observed in spectra of primitive asteroids and carbonaceous meteorites and has been attributed to the Fe2+-Fe3+ intervalence charge transfer associated with hydrated clay-bearing phyllosilicates. Craters The color of the largest craters (>100 m) on Bennu is indistinguishable from that of the average terrain. However, many small (&#8804;25 m) craters are redder than average across MapCam b&#8242; to x filters, resulting in neutral to red spectral slopes. The size distribution of these small reddish craters implies that they are the youngest component of the global crater population. References Lauretta, D. S., et al. &#8220;OSIRIS-REx: sample return from asteroid (101955) Bennu.&#8221; Space Science Reviews 212.1-2 (2017): 925-984. Rizk, B., et al. &#8220;OCAMS: the OSIRIS-REx camera suite.&#8221; Space Science Reviews 214.1 (2018): 26. Golish, D. R., et al. &#8220;Ground and in-flight calibration of the OSIRIS-REx camera suite.&#8221; Space Science Reviews 216.1 (2020): 12. Golish, D. R., et al. &#8220;Disk-resolved photometric modeling and properties of asteroid (101955) Bennu.&#8221; Icarus (2020): 113724. DellaGiustina, D. N., and Kaplan, H. H., et al. &#8220;Exogenic basalt on asteroid (101955) Bennu&#8221;. Nature Astronomy, in revision. Reuter, D.C., et al. &#160;&#8220;The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu&#8221;. Space Science Reviews 214.1 (2018): 54.&#160;

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The Temperature Dependence of an Absorption Feature in the Vicinity of the Long Wavelength Transmission Cutoff in ZnSe

Applied Spectroscopy ◽

10.1366/000370278774331503 ◽

1978 ◽

Vol 32 (2) ◽

pp. 164-167

Author(s):

P. M. Castle ◽

V. A. Toth

Keyword(s):

Temperature Dependence ◽

Data Storage ◽

Variable Temperature ◽

Infrared Absorption Spectrum ◽

Absorption Feature ◽

Phonon Interaction ◽

Difference Spectra ◽

Long Wavelength ◽

Infrared Spectrometer ◽

Temperature Liquid

The temperature dependence of the infrared absorption spectrum of ZnSe was measured by using a variable temperature, liquid nitrogen cooled, absorption cell interfaced with a Fourier transform infrared spectrometer. Absorption difference spectra were obtained as a function of temperature by using the on-board computing facilities of the spectrometer coupled with its data storage capabilities. The temperature dependence of the absorption feature, which extends from about 450 to 800 cm −1, is shown to be consistent with a two phonon interaction as have been previously suggested.

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The Eclipsing Binary WX Eridani

International Astronomical Union Colloquium ◽

10.1017/s0252921100073656 ◽

1979 ◽

Vol 46 ◽

pp. 385

Author(s):

M.B.K. Sarma ◽

K.D. Abhankar

Keyword(s):

Light Curve ◽

Spectral Type ◽

Orbital Period ◽

Primary Component ◽

Light Curves ◽

Absorption Feature ◽

Primary Star ◽

Eclipsing Binary ◽

The Times ◽

Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

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