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

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’.

scholarly journals Detection of Water Maser Emission from a Carbon Star V778 Cygni

1988 ◽  
Vol 108 ◽  
pp. 53-54
Author(s):  
Y. Nakada ◽  
H. Izumiura ◽  
T. Onaka ◽  
O. Hashimoto ◽  
N. Ukita ◽  
...  
Keyword(s):  
Carbon Star ◽  
Emission Feature ◽  
Circumstellar Envelopes ◽  
Gas Phase Chemistry ◽  
Evolved Stars ◽  
Molecular Lines ◽  
Circumstellar Shells ◽  
M Stars ◽  
Phase Chemistry ◽  
Water Maser

Infrared spectra of evolved stars are generally dominated by the radiation from their circumstellar shells. M stars are characterized by the 10 μm emission feature from silicate dust grains, while C stars by the 11 μm SiC band. However, some C stars have been found to show the 10 μm feature indicating the oxygen-rich property of their circumstellar dust (Willems and de Jong 1986, Little-Marenin 1986).In order to investigate the gas phase chemistry of the circumstellar envelopes around these peculiar objects, we have observed radio molecular lines of H2O, SiO, HCN, and CO towards three of them BM Gem (C5, 4J), V778 Cyg (C4, 5J), and EU And (C4, 4).

scholarly journals The 8-22μm Excess in Carbon Stars From IRAS LRS Spectra

1989 ◽  
Vol 106 ◽  
pp. 402-402
Author(s):  
S. J. Little ◽  
I. R. Little-Marenin
Keyword(s):  
Dust Emission ◽  
Unknown Origin ◽  
Carbon Star ◽  
Variable Stars ◽  
Emission Feature ◽  
Absorption Feature ◽  
Carbon Stars ◽  
Mira Variables ◽  
Period Variable ◽  
Ir Emission

We have measured the excess IR emission from carbon mira and SR variable stars from IRAS LRS spectra. The 8-22μm excess is defined as the ratio of flux above a 2500K energy distribution fit to the LRS spectrum at about 8μm. The carbon star LRS spectra show both emission and absorption features, which are incorporated into our 8-22pm excess. The most prominent feature in carbon stars is the 11.2μm SiC dust emission feature extending from 10μm to 13.8 μm. We observe another emission feature of unknown origin which peaks between 8.4-8.7μm. The SiC emission feature is occasionally blended on the red side by an absorption feature (attributed to gaseous HCN + C2H2) which extends from about 12-16μm. Many of the spectra appear to turn down at the 8μm end due (?) to an HCN + C2H2 absorption feature located at 7.1μm. Carbon stars do not generally show as large an excess as the M mira variables do. The figure below shows our measured excesses for both carbon miras and carbon semi-regular variables. There appears to be little correlation of excess with period, however the mira variables show about twice the range of variation of excess that the semi-regular variables do. We find little correlation between our measured 8-22μm excess and the excesses of Jura (Ap. J., 303, 327, 1986) based on the ratio of 12μm flux to 2μm flux. Our data do support hi s conclusion that longer period variable stars show larger average excesses, but this is only true for mira variables in our analysis.

scholarly journals HST UV Observations of the Disk and Wind of V795 Her

1996 ◽  
Vol 158 ◽  
pp. 43-44
Author(s):  
S. R. Rosen ◽  
R. K. Prinja ◽  
J. E. Drew ◽  
K. O. Mason ◽  
S. B. Howell
Keyword(s):  
Line Profile ◽  
Emission Feature ◽  
Absorption Feature ◽  
Absorption Component ◽  
Orbital Variation

AbstractHST UV observations of V795 Her reveal a strong 2.6-h orbital variation in the prominent UV lines, in contrast to earlier (IUE) evidence of a 4.8-h period. Only the C IV line contains a strong blue-shifted, wind formed absorption component. Several lines exhibit a ‘narrow’ absorption feature near rest velocity which may originate in the disk, and a blue-shifted emission feature which accounts for most of the line profile variability.

scholarly journals Reproduction of the Interstellar Ice Band by Grain Mantle Analogs

1980 ◽  
Vol 87 ◽  
pp. 387-388
Author(s):  
W. Hagen ◽  
A.G.G.M. Tielens ◽  
J. M. Greenberg
Keyword(s):  
Low Temperature ◽  
Interstellar Dust ◽  
Near Infrared ◽  
Absorption Feature ◽  
Band Shape ◽  
Interstellar Ice ◽  
Infrared Spectrometer ◽  
Simple Molecules ◽  
Many Sources ◽  
Dust Grain

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.

scholarly journals Is there a signature of ice in the IRAS LRS spectra of some Mira variables?

1987 ◽  
Vol 122 ◽  
pp. 221-222
Author(s):  
M. S. Vardya
Keyword(s):  
Emission Feature ◽  
Mira Variables ◽  
Broad Emission ◽  
New Feature

Some M Miras show the 9.7 and 20μm silicate emission. Recently, Vardya, de Jong & Willems (1986; hereafter VDJW) discovered using IRAS LRS spectra a weak broad emission feature ~12μm; this new feature may be silicate (VDJW). Here we investigate whether this can be due to H2O ice.

scholarly journals The period–luminosity relation of Mira variable stars

2012 ◽  
Vol 8 (S289) ◽  
pp. 217-217
Author(s):  
Akiharu Nakagawa ◽  
Tomoharu Kurayama ◽  
Toshihiro Omodaka ◽  
Tatsuya Kamezaki ◽  
Yoshiro Nishida ◽  
...  
Keyword(s):  
Very Long Baseline Interferometry ◽  
Variable Stars ◽  
Distance Measurement ◽  
Current Status ◽  
Long Baseline ◽  
Mira Variables ◽  
Mira Variable ◽  
Interferometry Method

AbstractWe use astrometry to measure the distances to Galactic Mira variable stars. Our purpose is to determine a precise period–luminosity relation (PLR). At present, we do not have a precise PLR for Galactic Mira stars because of the large uncertainties affecting their distance estimates. To reduce the uncertainties, we adopted the Very Long Baseline Interferometry method and measured annual parallaxes of Mira variable stars with VERA. In addition to our previous results, we obtained three new distances for Mira variable stars. Based on our observations, the typical uncertainty in a given distance measurement is reduced to below 10%. At this conference, we present the current status of our project. To establish a precise Galactic PLR, we continue to observe more Mira variables. In addition, the apparent magnitudes of the target stars should be studied carefully.

Investigating the Chemical Composition of the CIRS-Observed 160 cm-1 Ice Cloud in Titan’s Stratosphere

2020 ◽  
Author(s):  
Melissa Ugelow ◽  
Carrie Anderson
Keyword(s):  
Chemical Composition ◽  
Emission Feature ◽  
Individual Species ◽  
Ice Clouds ◽  
Mixing Ratios ◽  
Ice Cloud ◽  
Near Ir ◽  
Infrared Spectral ◽  
Infrared Spectrometer ◽  
The Individual

<p>Remote sensing observations from Voyager 1’s InfraRed Interferometer Spectrometer (IRIS) and Cassini’s Composite InfraRed Spectrometer (CIRS) confirmed the presence of nitrile ice clouds in Titan’s stratosphere (Samuelson 1985, 1992; Khanna, R.K. et al., 1987; Samuelson et al., 1997, 2007; Coustenis, A. et al., 1999; Mayo and Samuelson, 2005; Anderson, C.M. et al., 2010, 2018a,b; Anderson and Samuelson, 2011). While individual gases in Titan’s stratosphere are expected to condense to form pure ices, some of these gases will enter altitude regions where they undergo simultaneous saturation, or co-condensation, and form a mixed ice. The infrared spectral features resulting from a mixed ice have their own unique spectral signatures that notably diverge from the weighted sum of the individual species, and must therefore be experimentally determined as functions of temperature and mixing ratio (Anderson and Samuelson, 2011; Anderson et al. 2018a,b).</p> <p>The first observation of a co-condensate in Titan’s stratosphere was acquired by CIRS, which revealed a spectrally broad quasi-continuum ice emission feature with a spectral peak near 160 cm<sup>-1</sup>.  Based on the altitude of the observed cloud top, combined with preliminary experimental efforts (Anderson and Samuelson, 2011), the co-condensate was determined to predominately contain cyanoacetylene (HC<sub>3</sub>N) and hydrogen cyanide (HCN). Here we present experimentally-measured absorbance spectra for the far-, mid-, and near-IR spectral regions (1.25 – 200 µm; 8000 – 50 cm<sup>-1</sup>), along with the corresponding optical constants, of HC<sub>3</sub>N-HCN co-condensed ices utilizing the SPECtroscopy of Titan-Related ice AnaLogs (SPECTRAL) Chamber (Anderson et al., 2018a). Various deposition temperatures and mixing ratios of mixed HC<sub>3</sub>N and HCN were systematically studied to quantify the chemical composition of Titan’s CIRS-observed 160 cm<sup>-1</sup> stratospheric ice cloud emission feature.</p>

scholarly journals Ammonia in circumstellar environment of V Cyg

2020 ◽  
Vol 10 (1) ◽  
pp. 7-11
Author(s):  
B. Etmański ◽  
M. Schmidt ◽  
R. Szczerba
Keyword(s):  
Background Radiation ◽  
Spectral Energy Distribution ◽  
Careful Analysis ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Theoretical Predictions ◽  
Red Supergiants ◽  
Molecular Lines

The HIFI instrument on board of the Herschel Space Observatory (HSO) has been very successful in detecting molecular lines from the circumstellar envelopes around evolved stars, like massive red supergiants, Asymptotic Giant Branch (AGB) and post-AGB stars, as well as the planetary nebulae. Among others, ammonia have been found in the circumstellar envelopes of C-rich AGB stars in amounts that significantly exceeded the theoretical predictions for C-rich stars. Few scenarios have been proposed to resolve this problem: formation of ammonia behind the shock front and photochemical processes in the inner part of the envelope partly transparent to UV background radiation due to the clumpy structure of the gas and formation of ammonia on dust grains. Careful analysis of observations may help to put the constraints on one or another mechanism of ammonia formation. Here, we present results of the non-LTE radiative transfer modeling of ammonia transitions including the crucial process of radiative pumping via the v2=1 vibrational band (at ∼10 μm) for V Cyg. Only the ground-based ammonia transition NH3 J = 10-00 at 572.5 GHz has been observed by HIFI. Therefore, to determine the abundance of ammonia we estimate the photodissociation radius of NH3 using chemical model of the envelope consistent with the dust grain properties concluded from the spectral energy distribution.

scholarly journals Radio Observations of Mira Variables, OH/IR Stars and M-Supergiants

1995 ◽  
Vol 155 ◽  
pp. 113-126
Author(s):  
Jessica M. Chapman ◽  
H. J. Habing ◽  
N. E. B. Killeen
Keyword(s):  
Circumstellar Envelopes ◽  
Radio Observations ◽  
Mira Variables ◽  
Ir Stars

AbstractWe review radio maser observations of the circumstellar envelopes of oxygen-rich Mira variables, OH/IR stars and M-type supergiants.

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