IRAS Low-resolution Spectra Research Articles

Ten-micron Emission in a Color–magnitude Diagram of M Giant Variables

Infrared color–magnitude diagrams are presented for variable M giants within the Two-Micron Sky Survey for which 10 μm dust emission was detected in IRAS low-resolution spectra. Dust emission is mostly limited to a definable region in absolute M Ks magnitude and (J − K s ) color, and to pulsation periods greater than 50 days.

Investigation of Faint Galactic Carbon Stars from the First Byurakan Spectral Sky Survey. III. Infrared Characteristics

Infra-Red(IR) astronomical databases, namely, IRAS, 2MASS, WISE, and Spitzer, are used to analyze photometric data of 126 carbon stars whose spectra are visible in the First Byurakan Survey low-resolution spectral plates. Among these, six new objects, recently confirmed on the digitized FBS plates, are included. For three of them, moderate-resolution CCD optical spectra are also presented. In this work several IR color-color diagrams are studied. Early and late-type C stars are separated in the JHK Near-Infra-Red(NIR) color-color plots, as well as in the WISE W3-W4 versus W1-W2 diagram. Late N-type Asymptotic Giant Branch stars are redder in W1-W2, while early-types(CH and R giants) are redder in W3-W4 as expected. Objects with W2-W3 > 1.0 mag. show double-peaked spectral energy distribution, indicating the existence of the circumstellar envelopes around them. 26 N-type stars have IRAS Point Source Catalog(PSC) associations. For FBS 1812+455 IRAS Low-Resolution Spectra in the wavelength range 7.7 - 22.6micron and Spitzer Space Telescope Spectra in the range 5 - 38micro are presented clearly showing absorption features of C2H2(acetylene) molecule at 7.5 and 13.7micron , and the SiC(silicone carbide) emission at 11.3micron. The mass-loss rates for eight Mira-type variables are derived from the K-[12] color and from the pulsation periods. The reddest object among the targets is N-type C star FBS 2213+421, which belong to the group of the cold post-AGB R Coronae Borealis(R CrB) variables.

Identification of new silicate carbon stars

IRAS low-resolution spectra for 17 sources are presented in this paper. Together with the carbon star catalog, information from recent literatures, the ISO observation and the IRAS two-color diagram, it is found that among them 5 sources are new silicate carbon stars, 5 sources are candidates of silicate carbon stars and other 7 sources are probable candidates of silicate carbon stars. Some discussions are made for their infrared properties.

Infrared study of the extreme carbon stars based on IRAS, 2MASS and ISO data

We collected 55 galactic extreme carbon stars from the published literature in this paper. Observational data from IRAS, 2MASS and ISO were analyzed. The results show that the infrared properties of extreme carbon stars are quite different to those for ordinary visual carbon stars. It is shown from IRAS and 2MASS photometric data that extreme carbon stars have much redder infrared colors not only in the far infrared, but also in the near infrared, hence they have much thicker ciucumstellar envelopes and mass loss. It is also indicated from IRAS Low-Resolution Spectra (LRS) and ISO Short Wavelength Spectra (SWS) that they have much redder infrared spectra from 2 mu m to 45 mu m. The above results are believed to be the signature of undergoing the last stages of AGB evolution for extreme carbon stars.

Newly Identified Silicate Carbon Stars from IRAS Low-Resolution Spectra

The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identifications between the new IRAS Low-Resolution Spectrum (LRS) database and the new carbon star catalog, CGCS3. We have found nine new silicate carbon stars with silicate features around 10 mu m and/or 18 mu m. These newly identified stars are located in the Regions IIIa and VII in the IRAS two-color diagram, which means they indeed have typical far infrared colors of silicate carbon stars. The infrared properties of each of these sources are discussed.

A new approach to IRAS observations of Be stars

The IRAS associations for 193 Be stars are identified in this paper. From the infrared colors, the IRAS low-resolution spectra (LRS) and the spectral types, some physical properties and environment of the samples are discussed. It can be concluded that not only free-free emission or free-bound emission from the circumstellar ionized gas can be responsible for the large IR excesses of Be stars as suggested previously, but also, for some Be stars, thermal radiation from the circumstellar dust and/or nebula around the star can produce large IR excess as well. It is also found that the far IR excess of Be stars increases with wavelengths.

Discussion on candidates for the M stars with 11.2 μm SiC feature

The oxygen-rich stars with SiC emission features are unexpected according to the evolutionary theory in the late stage of stellar evolution. After the careful re-examination of such samples reported previously and searching for new samples, seven stars are found to be the candidates of the M stars with 11.2 μm SiC emission feature. However, with the IRAS low-resolution spectrum, the IRAS two colour diagram and other information, it is seen that no strong candidates for oxygen-rich AGB stars with carbon-rich circumstellar dust could be found so far.

Newly Identified Infrared Carbon Stars from the [ITAL]IRAS[/ITAL] Low-Resolution Spectra

We report new identifications of 63 infrared carbon stars and 24 possible candidates based on the presence of the SiC emission feature at 11.2 μm in their IRAS low-resolution spectra and on their infrared colors. The IRAS spectra of the newly identified carbon stars are presented.

Infrared low-resolution spectra of symbiotic stars

The IRAS low-resolution spectra (LRS) of 29 symbiotic stars are presented in this paper. It is found that silicate dust is common material in the circumstellar shells of symbiotic stars. From the IRAS low-resolution spectra, IRAS colors, symbiotic types and spectral types, some physical properties of symbiotic stars with the LRS spectra are also discussed.

Infrared spectra of T Tauri stars

We present IRAS low-resolution spectra for 26 T Tauri stars and, based on the spectra, discuss the properties and environment of these stars. The analysis reveals that silicate dust is a common material in the circumstellar shells of T Tauri stars.

Herbig Ae/Be stars with the IRAS low-resolution spectra

IRAS low-resolution spectra are presented for 36 HAEBE stars. It is found that silicate dust is common material in the circumstellar disks or/and shells of HAEBE stars. It is also found that the PAH feature often appears as well. In addition, the correlation between the dust features and spectral type, and infrared excesses can be found for most HAEBE stars.

Spectral Irradiance Calibration in the Infrared. IX. Calibrated Stellar Spectra Using DIRBE Radiometry

The absolute calibration of the COBE/DIRBE data in the range 1–25 μm is examined through the in-band fluxes of DIRBE's own set of point-source calibration objects. Using the values of DIRBE fluxes expected for Sirius and for 10 of our published set of absolutely calibrated K and M giants that are in common with DIRBE's own calibration network, I find consistency with the project's formal basis, namely, our published calibrated spectrum of Sirius. This consistency means that one can use the DIRBE radiometry to construct absolutely calibrated templates (i.e., continuous calibrated spectra from 1 to 35 μm) on the assumption that the intrinsic stellar spectrum of a star of given spectral class matches the intrinsic spectrum for the star of the same spectral class among the set of K and M giants, the spectrum of which has been absolutely defined. This technique is validated using a set of early M giants with well-characterized ground-based photometry and confirmed with IRAS low-resolution spectra.

Classification and Identification of IRAS Sources with Low‐Resolution Spectra

IRAS low-resolution spectra were extracted for 11,224 IRAS sources. These spectra were classified into astrophysical classes, based on the presence of emission and absorption features and on the shape of the continuum. Counterparts of these IRAS sources in existing optical and infrared catalogs are identified, and their optical spectral types are listed if they are known. The correlations between the photospheric/optical and circumstellar/infrared classification are discussed.

Four Newly Identified Sources with 21 Micron Emission

view Abstract Citations (57) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Four Newly Identified Sources with 21 Micron Emission Kwok, Sun ; Hrivnak, Bruce J. ; Geballe, T. R. Abstract Mid-infrared spectroscopy and near- and mid-infrared photometry have been obtained for four carbon-rich cool IRAS sources whose IRAS low-resolution spectra are similar to those of proto-planetary nebulae (PPNs) possessing the unusual 21 microns emission feature. The 21 microns feature is detected in all four sources, nearly doubling the number of known 21 microns emitters. The energy distributions of these objects show the characteristic "double-peaked" structure, confirming that they are PPNs. Broad features near 7.7 and 11.3 microns similar to the unidentified infrared features (UIRs) seen in carbon-rich planetary nebulae (PNs) are also detected, suggesting a chemical link between these PPNs and PNs. The presence of the 21 microns feature appears to be correlated with the presence of unusually strong 3.4-3.5 microns features. Possible scenarios for the evolution of these emission features in the PPN phase are discussed. Publication: The Astrophysical Journal Pub Date: November 1995 DOI: 10.1086/176490 Bibcode: 1995ApJ...454..394K Keywords: STARS: CIRCUMSTELLAR MATTER; INFRARED: STARS; ISM: PLANETARY NEBULAE: GENERAL; STARS: CARBON full text sources ADS | data products SIMBAD (23)

INFRARED PROPERTIES OF STARS ON THE ASYMPTOTIC GIANT BRANCH. SEMIREGULAR VARIABLE STARS OF TYPES SRA AND SRB

ABSTRACT Samples of optical semiregular variables (SRV's) of types SRa and SRb are correlated with the IRAS point source catalog. We extract bolometrically limited subsamples containing 352 objects in total. New near infrared photometry and data from the literature leads to complete energy distributions for 260 stars. On the basis of optical and IRAS low-resolution spectra we separate the samples into groups of defined chemistry, in particular C- and O-rich stars. The pulsational properties, visual and infrared colours, derived effective temperatures, mass loss rates, luminosities, scale heights and volume densities in the galactic plane of our subsamples are compared with corresponding characteristics of optical Miras. Moreover, it is possible to fit two blackbodies to most of the objects using visual and new near infrared photometry as well as mid and far infrared IRAS data. The resulting temperatures and other fit parameters support the findings gathered from the previous investigation. The results concerning variability and chemistry can be summarised as follows: (i) The SRa's are not a distinct class of variables but a mixture of 'intrinsic' Miras and SRb's. (ii)~The O-rich SRb's form a homogeneous group in terms of periods, amplitudes and temperatures. They consist of a 'blue' group with no indication of circumstellar matter, P < 150d and Teff > 3200 K and a 'red' group with temperatures and mass loss rates comparable to those of Miras but with periods a factor of 2 smaller. Scale heights and number densities are similar for 'red' SRV's and Miras. 'Blue' SRV's are about twice as numerous as the 'red' ones, half as luminous and without C-rich stars. (iii) The C-rich SRV's generally have smaller periods and are more abundant than C-rich Miras but their scale heights closely agree. (iv) Among all groups there are stars with much longer periods than expected from their temperatures and mass loss rates. This may be due to observational effects, irregular light curves or multiple periods. (v) A new classification scheme for O-rich SRV's and Miras in the groups 'blue' SRV's, 'red' SRV's and true Miras is proposed using period, amplitude and colours. The evolutionary status of the SRV's is discussed. On the basis of temperatures, luminosities, mass loss and number densities, the 'blue' SRV's appear to be on the non thermally pulsing AGB. One of the interpretations for O-rich 'red' SRV's is in terms of a phase preceding the Mira phase, with similar life times. The C-rich SRV's may show more variety in their pulsational characteristics.

UKIRT CGS3 Observations of New IRAS 21 Micron Sources

An unidentified emission feature at 21 μm has been detected in the IRAS Low Resolution Spectra (LRS) of 5 IRAS sources (Kwok, Volk, and Hrivnak 1989, Hrivnak and Kwok 1991). The sources are generally found to be F and G supergiants with cool, detached dust shells. We have searched for additional 21 μm sources in the LRS database and have obtained ground-based UKIRT spectra at 10 and 20 μm in an attempt to confirm the LRS feature.

Candidates for extreme carbon stars

view Abstract Citations (81) References (45) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Candidates for Extreme Carbon Stars Volk, Kevin ; Kwok, Sun ; Langill, Philip P. Abstract A group of candidates for extreme carbon stars has been identified based on their IRAS low-resolution spectra being similar to those of AFGL 3068 and IRC +10 deg 216, which are prototypes of highly evolved carbon stars with very high mass-loss rates. Ground-based photometry has been obtained for five of these sources in order to determine the peaks of their energy distributions. All five sources have color temperatures between 300 and 500 K, and have energy distributions very similar to AFGL 3068. The observed data are fitted with radiative transfer models with optical depths at 11.3 microns ranging from 1.4 to 8. These results suggest that these stars have among the most optically thick circumstellar envelopes of all carbon stars observed to date. Publication: The Astrophysical Journal Pub Date: May 1992 DOI: 10.1086/171344 Bibcode: 1992ApJ...391..285V Keywords: Asymptotic Giant Branch Stars; Carbon Stars; Stellar Envelopes; Stellar Evolution; Color-Color Diagram; Infrared Astronomy Satellite; Spectral Energy Distribution; Spectral Resolution; Stellar Spectra; Stellar Spectrophotometry; Astrophysics; STARS: CIRCUMSTELLAR MATTER; INFRARED: STARS; STARS: CARBON full text sources ADS | data products SIMBAD (33)

On the occurrence of carbon dioxide in interstellar grain mantles

The detection of solid CO on dust grains in dense molecular clouds leads to the prediction that CO 2 is also present in solid form, and a detection of the expected CO 2 feature at 15.2 μm in IRAS low-resolution spectra (LRS) of the protostellar object AFGL 961 was recently reported. The results of a search of the LRS database for sources selected on the basis of strong water-ice absorption at 3 μm in ground-based spectra are presented

Enrichment by Wolf-Rayet Stars and Other Massive Stars in Gas, Dust and Energy

I update previous estimates of the separate contributions for radiative energy, integrated total stellar wind mass and dust mass from Wolf-Rayet stars and other massive (OBA) stars. In the context of the intriguing dusty WC9 stars, I: (1) discuss the observability (or otherwise) between 0.4 and 23 μm of the condensation route from hot gas to carbon-rich grains; (2) urge caution in the use of 10 μm infrared spectra of these luminous stars to deduce the importance of silicates as a component of the interstellar medium, and (3) speculate on a possible new method for discovering new members of this relatively rare subtype based on IRAS Low Resolution Spectra. I review the observational evidence for dust condensation around SN 1987A.

On the nature of G25.5 + 0.2 - The IRAS low-resolution spectrum of IRAS 18344 - 0632

The IRAS low-resolution spectrum of IRAS 81344 - 0632, which may be associated with the proposed (Cowan et al., 1989) very young supernova remnant G25.5 + 0.2, is presented. This spectrum shows a red continuum, and the 12.8-micron Ne II forbidden line, and is similar to the spectra of known compact H II regions and planetary nebulae. This, together with other results, suggests that IRAS 18344 - 0632 and G25.5 + 0.2 are associated, and are a planetary nebula not a young supernova remnant, although it is difficult to reconcile this identification with all available observations. 15 refs.