共查询到20条相似文献,搜索用时 316 毫秒
1.
P. Ehrenfreund E.F. Van Dishoeck M. Burgdorf J. Cami P. Van Hoof A.G.G.M. Tielens W.A. Schutte W.F. Thi 《Astrophysics and Space Science》1997,255(1-2):83-89
We present ISO observations of bright, high-mass southern starforming regions with the Short Wavelength Spectrometer (SWS)
and Long Wavelength Spectrometer (LWS). The selected targets show a range of pre-main sequence evolutionary phases. Whereas
some objects still show interstellar ice features, the most evolved objects are coincident with ultra-compact HII regions
and show strong emission lines from atomic species and polycyclic aromatic hydrocarbons (PAHs). We discuss the ISO spectra
between 2.5 - 200 μm of selected southern star-forming regions in the context of their evolution.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
We report on SWS and LWS observations of the circumstellar disks of young stars of a few solar masses. The ISO spectra of
these objects present a diversity of emission features of carbon-rich and oxygen-rich grains. The similarity of the forsterite
spectra observed for Comet Hale-Bopp and the Haebe star HD100546 is particularly striking and provides a new argument that
huge comet swarms are formed in the disks surrounding young stars. While the data suggest that the formation of crystalline
silicates in the dust disks essentially occurs when a Haebe star has already reached the main sequence, no clear correlation
with stellar age only is apparent.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
Th. Boller 《Astrophysics and Space Science》1999,266(1-2):49-54
A sample of 323 Ultraluminous IRAS galaxies (ULIRGs) has been correlatedwith the ROSAT All-Sky Survey and ROSAT public pointed observations.22 objects are detected in ROSAT survey observations, and 6 ULIRGs aredetected in addition in ROSAT public pointed observations. The detection is basedon a visual inspection of the X-ray contour maps overlaid on optical imagesof ULIRGs taken from the Digitized Sky Survey.Simple power law fits were used to compute the absorption-correctedfluxes of the ROSAT detected ULIRGs. The ratio of the soft X-ray flux to thefar-infrared luminosity is used to estimate the contributionfrom starburst and AGN emitting processes. These results are comparedwith the ISO SWS ULIRG diagnostic diagram. 相似文献
4.
S.P.S. Eyres A. Evans A. Salama P. Barr J. Clavel N. Jenkins K. Leech M. Kessler T. Lim L. Metcalfe B. Schulz 《Astrophysics and Space Science》1997,255(1-2):361-366
A number of symbiotic stars have been observed with ISO. In addition to a number of emission lines, SWS observations of the
symbiotic novae RR Tel and V1016 Cyg reveal prominent, broad 10 & 18 μm silicate dust features. The 10 μm features are similar
to the crystalline silicate profiles seen in classical novae. There is some evidence that the silicate brightness in V1016
Cyg varies with Mira-component phase. However, the silicate feature in RR Tel also showed some variation even though observations
were made at very similar Mira-component phases. PHT observations of S-type symbiotic stars show the IR emission to be dominated
by the red-giant component. However, an excess in the PHT-P filters from 10 to 15 μm is evident in all the stars, and there
may be a broad 3.2 μm absorption feature or a broad 3.8 μm emission feature. At this time we have no adequate physical explanations
for any of these features.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
E. LellouchB. Bézard J.I. MosesG.R. Davis P. DrossartH. Feuchtgruber E.A. BerginR. Moreno T. Encrenaz 《Icarus》2002,159(1):112-131
Observations of H2O rotational lines from the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite (SWAS) and of the CO2 ν2 band by ISO are analyzed jointly to determine the origin of water vapor and carbon dioxide in Jupiter's stratosphere. Simultaneous modelling of ISO/LWS and ISO/SWS observations acquired in 1997 indicates that most of the stratospheric jovian water is restricted to pressures less than 0.5±0.2 mbar, with a disk-averaged column density of (2.0±0.5)×1015 cm−2. Disk-resolved observations of CO2 by ISO/SWS reveal latitudinal variations of the CO2 abundance, with a decrease of at least a factor of 7 from mid-southern to mid-northern latitudes, and a disk-center column density of (3.4±0.7)×1014 cm−2. These results strongly suggest that the observed H2O and CO2 primarily result from the production, at midsouthern latitudes, of oxygenated material in the form of CO and H2O by the Shoemaker-Levy 9 (SL9) impacts in July 1994 and subsequent chemical and transport evolution, rather than from a permanent interplanetary dust particle or satellite source. This conclusion is supported by quantitative evolution model calculations. Given the characteristic vertical mixing times in Jupiter's stratosphere, material deposited at ∼0.1 mbar by the SL9 impacts is indeed expected to diffuse down to the ∼0.5 mbar level after 3 years. A coupled chemical-horizontal transport model indicates that the stability of water vapor against photolysis and conversion to CO2 is maintained over typically ∼50 years by the decrease of the local CO mixing ratio associated with horizontal spreading. A model with an initial (i.e., SL9-produced) H2O/CO mass mixing ratio of 0.07, not inconsistent with immediate post-impact observations, matches the observed H2O abunda nce and CO2 horizontal distribution 3 years after the impacts. In contrast, the production of CO2 from SL9-produced CO and a water component deriving from an interplanetary dust component is insufficient to account for the observed CO2 amounts. The observations can further be used to place a stringent upper limit (8×104 cm−2 s−1) on the permanent water influx into Jupiter. This may indicate that the much larger flux observed at Saturn derives dominantly from a ring source, or that the ablation of micrometeoroids leads dominantly to different species at Saturn (H2O) and Jupiter (CO). Finally, the SWAS H2O spectra do not appear fully consistent with the ISO data and should be confirmed by future ODIN and Herschel observations. 相似文献
6.
Observations of 5 stellar sources with unusual characteristics of IRAS Low Resolution Spectra were made with the SWS on ISO.
Observed stars are 4 late-type stars with silicate bands and one planetary nebula. Their IRAS LRS contain somewhat unusual
features in respect of the 10/18 μm intensity ratio or narrow emission feature from unknown molecular bands. Some narrow unusual
features are confirmed by ISO SWS01 spectra but the broad features were turned out to be false.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
R. Szczerba S.K. GÓrny G. StasiŃska N. SiÓdmiak R. Tylenda 《Astrophysics and Space Science》2001,275(1-2):113-119
We present Infrared Space Observatory (ISO)Short Wavelength Spectrometer (SWS) observations for 16Wolf–Rayet ([WR]) planetary nebulae (PNe) in the range from 2.4 to16.5 m with the aim of analyzing the dust features present inthis group of objects. We have found that Policyclic AromaticHydrocarbon (PAH) molecular bands are present in most of the observed[WR] planetary nebulae with clear exception for K 2–16 among latetype [WC] stars. 相似文献
8.
J. Cami T. De Jong K. Justtannont I. Yamamura L.B.F.M. Waters 《Astrophysics and Space Science》1997,255(1-2):339-340
We present the spectra of 5 OH/IR stars observed with the Short Wavelength Spectrometer (SWS) on board the Infrared Space
Observatory (ISO). The spectra are dominated by dust features, both in the amorphous and crystalline state and illustrate
the influence of the mass loss rate on the observed spectral features.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Overall SEDs based on ISO SWS observations show fair agreement with photospheric model predictions for red (super)giant stars.
However, some details of molecular spectra cannot be explained by a photospheric origin. In particular, fine structure in
the H2O 2.7 μm band can be clearly resolved by the SWS and is identified in an early M giant, whose photosphere will never
produce H2O. This is definite evidence for H2O of non-photospheric origin in an early M giant. Also, the observed H2O and
CO2 bands in a late M giant are too strong to be explained by a photospheric origin alone. Further, the H2O 2.7 μm band is
found in four early M supergiants in the h + χ Persei clusters (three of which show UIRs) and is especially strong in the
M4 supergiant S Per (which also shows a highly peculiar SED). Thus, against a belief that H2O is found only in the latest
M giants such as Miras, the SWS has revealed the presence of H2O in a wider region of the HR diagram. The origin of this H2O
is unknown but is probably in a non-photospheric extra envelope. Such a H2O envelope appears to be a general feature through
early M (super)giants to cool supergiants such as S Per, where the envelope has finally developed to be optically thick.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
M.A. BarucciE. Dotto J.R. BrucatoT.G. Müller P. MorrisA. Doressoundiram M. Fulchignoni M.C. De SanctisT. Owen J. CrovisierA. Le Bras L. ColangeliV. Mennella 《Icarus》2002,156(1):202-210
Observations of emissivity features of 10 Hygiea have been made for the first time in the relatively unexplored thermal-infrared wavelength region with the ISO (Infrared Space Observatory) satellite. Spectrophotomer (PHT-S) and short wavelength spectrometer (SWS) spectra of 10 Hygiea, obtained at 5.8-11.6 and 7-45 μm, respectively, are presented. In order to remove the thermal emission continuum, an advanced thermo-physical model has been applied to the observational data. To better interpret the spectral features above the thermal emission continuum, we compared the ISO observations with laboratory spectra available in the literature. Several laboratory experiments on minerals and meteorites have been performed to complete the analysis and to study the spectral behavior at various grain sizes. A possible spectral similarity with CO carbonaceous chondrites at small grain size is demonstrated. 相似文献
11.
E.F. Van Dishoeck W.F. Thi G.A. Blake V. Mannings A.I. Sargent D. Koerner L.G. Mundy 《Astrophysics and Space Science》1997,255(1-2):77-82
Preliminary results are presented of observations of the pure rotational lines of H2 toward T Tauri and Herbig Ae stars using
the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). The sources are selected to be isolated low-
and intermediate-mass young stellar objects, for which the presence of a circumstellar disk has been established by millimeter
interferometry. The lowest H2 S(0) and S(1) lines are detected in 3 out of 5 objects. The measured intensities indicate ∼
0.01 M⊙ of warm (T ≈ 150 K) gas in the ISO beam. It is argued that for at least one case (HD 163296), the emission is probably
dominated by the warm gas in the circumstellar disk rather than by shocked- or photon-heated gas in the surrounding envelope.
Such observations can provide important constraints on the radial and vertical temperature profiles in circumstellar disks.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
The Infrared Space Observatory (ISO) Short-Wavelength Spectrometer (SWS) spectra of 10 Be stars are presented. It can be seen that the Be stars show a diversity in their ISO SWS01 spectral classifications by Kraemer et al., from naked stars, stars associated with dust, stars with warm dust shells, stars with cool dust shells to very red sources. In addition, the Brc/HI(14-6) line flux ratio derived for the sample stars is compared with that of P Cyg, and it is found that the line ratio of Be stars which were investigated show not only lower values as suggested by Waters et al., but also larger values. Therefore, the line ratio cannot he used to judge whether a star is a Be star or not. 相似文献
13.
K. Justtanont J. Cami I. Yamamura T. De Jong L.B.F.M. Waters 《Astrophysics and Space Science》1997,255(1-2):351-357
We have observed ten carbon stars with different mass-loss rates using the Short Wavelength Spectrometer (SWS) on board ISO.
We found that not only the spectral energy distribution and the dust features, but that also that the strength and/or shape
of molecular absorption features in the infrared spectrum varies with the near-infrared color temperature, i.e. with the thickness
of the circumstellar envelope.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
For this paper, we collected all infrared carbon stars (IRCSs) known so far from the literature and identified the 2MASS counterparts
of all IRCSs. Using 2MASS, IRAS and ISO SWS data, we investigate the infrared properties of IRCSs. We find that the infrared
colors and temperatures of IRCSs—not only in the IRAS region but also in the near infrared—are between those for visual carbon
stars and extreme carbon stars. The results in this paper strongly support the suggestion that the sequence of visual carbon
stars → infrared carbon stars → extreme carbon stars is the evolutionary sequence in the AGB phase for carbon-rich stars.
In addition, using the ISO SWS data, we find that an evolutionary sequence also exists within the IRCS stage. 相似文献
15.
A. M. Heras E. Wieprecht H. Feuchtgruber F. Lahuis K. Leech R. Lorente P. Morris A. Salama B. Vandenbussche 《Experimental Astronomy》2000,10(2-3):177-197
We present a trend analysis of the ISO-SWS detector performance and a study of the space radiation effects on the SWS detectors. In particular, dark currents, dark current noise and detector responses have been checked as a function of time through the mission and as a function of time in arevolution. The results show that these parameters were stable during the mission in all bandsbut for band 3 (Si:As). Dark currents and responses were found to be higherin the first hours following the start of the science window,especially in band 2 (Si:Ga). We have studied the impacts of cosmic rays and radiation belt particles on the SWS detectors, as well as of the only large solar proton event on November 6, 1997,that occurred during the ISO mission (operated during solar minimum).The observed glitch rates in all SWS bands are found to be between 2 and4 times higher than the value predicted by the CREME96 model for the cosmic ray flux in the period considered. The bands that registered the highest glitch rates showed also a correlation with the electron fluxes measured on theGOES 9 spacecraft. From the distribution of glitchheights (voltage jumps in the detector signal), we have derived the deposited energy distributions of the particles hits. Our results lead to the conclusion that secondaryparticles produced in the shield and the detectors contributed at least as much as cosmic rays to the observed glitch rate. The effects on the detectors of the November 6, 1997 event, which caused that all observationsin a revolution were declared failed, are described in detail. 相似文献
16.
D. Lutz E. Sturm R. Genzel A.F.M. Moorwood A. Sternberg 《Astrophysics and Space Science》1997,248(1-2):217-224
We present a first analysis of 2.4-45μm spectra of NGC 1068 obtained with the Short Wavelength Spectrometer SWS on board the
Infrared Space Observatory ISO. The measured fine-structure line fluxes can be fit successfully by a simple photoionization
model invoking an EUV bump in the ionizing continuum, similar to the case of the Circinus galaxy. Difference are observed
between the [OIV] 26μm NLR line profile and optical NLR line profiles which may indicate significant extinction to part of
the NLR. We detect pure rotational transitions of molecular hydrogen that must be emitted by molecular gas spanning a wide
range of temperatures. The unusual strength of the fundamental S(0) 28μm rotational transition is evidence for a large (>
1.5 × 109 M⊙) gas mass at temperatures nea r 100 K. Either most of the gas in the circumnuclear region of NGC 1068 is warm
or previous molecular mass estimates based on CO observations were too low. Strong mid-infrared continuum from the circumnuclear
warm dust is prominent in our spectrum. The weak PAH emission detected at the edges of the 9.7μm silicate absorption should
be considered in interpretations of the silicate feature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Dirk Froebrich Michael D. Smith Jochen Eislöffel 《Astrophysics and Space Science》2003,287(1-4):217-220
We present our analysis of four molecular outflows from Class 0 (Cep E,L 1448) sources and higher mass objects (Cep A, DR 21). The emission line spectra of these outflows were observed in the mid- and far-infrared using the spectrometers (SWS, LWS) and the camera (ISOCAM) aboard the ISO satellite. We interpret the spectra using J- and C-type bow shock models and infer properties of both the outflow and surrounding gas. We find C-type bows with a shape parameter of s = 1.4 as the best interpretation of the measured line fluxes, independent of the object. The emission is partly caused by fluorescence. 相似文献
18.
A.G.G.M. Tielens L.B.F.M. Waters F.J. Molster K. Justtanont 《Astrophysics and Space Science》1997,255(1-2):415-426
This paper reviews spectra obtained with the SWS on board of ISO of dust shells around O-rich objects. These spectra reveal
the presence of many new emission features between 10 and 45 μm. These bands are generally much narrower than the well-known
10 and 20 μm silicates features. The strength of these features relative to the underlying broad continuum varies from source
to source (≅ 5-50%). The 10 μm region shows evidence for the presence of Al2O3 grains. At longer wavelength, the spectra are
dominated by features due to crystalline olivine and pyroxene. The exact peak position of these features shows that the emitting
grains consist of the Mg-rich end-members of these minerals with an Fe-content of < 10%. The underlying continuum is attributed
to amorphous silicate grains.
These observations of aluminum-rich and magnesium-rich compounds compare well with the thermodynamic condensation sequence
of minerals expected for O-rich outflows. The observations also imply that freeze out (ie., kinetics) of this condensation
sequence at different temperatures is an important characteristic of dust formation in these objects. It is suggested that
the absence of Fe-rich silicates is a natural consequence of the low temperature at which gaseous Fe reacts with Mg-rich silicates
in these outflows, resulting in amorphous grains with little characterizing spectral detail.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
We have been awarded NASA Key Project observing time on ISO, in order to establish the true frequency of far-infrared excesses in a volume-limited sample of main sequence and related stars, and address the relative success or failure of single stars in processes related to the forming of planetary systems. For a volume-limited subset of main sequence and related stars, PHT03 measurements at 3.6, 11.5, 20 and 60 micron will be obtained, using a 120 arsec aperture in all cases to eliminate possible companion confusion with differing apertures, to ascertain spectral energy distributions. For the M dwarfs, 100 micron observations will also be obtained. For some, brighter sources, more extensive wavelength coverage and improved spatial resolution will be attempted, using CAM and SWS. Spatially over-sampled PHOT observations will be made at 60 micron of the brightest and nearest Vega-like sources to measure the characteristic sizes of the emitting regions and obtain some information regarding their shapes and orientations. The goal is not a map, but scan profiles along 3 position angles which can be deconvolved to find the intrinsic size and shape of the half-maximum contour of the emitting region. Photometry of selected lines of sight through the zodiacal dust will also be carried out to look for outer solar system (Kuiper Belt) material. Observation at a range of wavelengths, ecliptic latitudes and at 2 epochs is designed to help untangle foreground Zodiacal from background Kuiper flux, not necessarily to look for individual macroscopic objects. 相似文献
20.
We are currently conducting a search of oxygen-rich circumstellar envelopes for carbon-bearing molecules with the ISO SWS
instrument. CH4 is the molecule in which we are most interested, because it has been shown to be capable of providing the reactive carbon
which is needed produce the carbon-bearing molecules in these envelopes (Willacy & Millar 1997). However, CO2 and C2H2 are also possible candidates. The spectral ranges for our observations have been chosen specifically to include ro-vibrational
bands in these molecules, but many other molecules, such as HCN, NH3, OH and HO2 have bands in these regions and hopefully there will be a few interesting surprises.
To date we have received the observations of three of our objects, R Cas, IRC+10420 and the S-type star W Aql, which we are
observing to study the effect of the C/O ratio on chemical composition. Preliminary results for W Aql show little evidence
of CH4, a tentative detection of CO2, and clear evidence of OH and HCl.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献