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Search Results: 1 - 10 of 117873 matches for " T. Prusti "
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Mid infrared emission of nearby Herbig Ae/Be stars
R. Siebenmorgen,T. Prusti,A. Natta,Th. Mueller
Physics , 2000,
Abstract: We present mid IR spectro-photometric imaging of a sample of eight nearby ($D \leq 240$pc) Herbig Ae/Be stars. The spectra are dominated by photospheric emission (HR6000), featureless infrared excess emission (T~Cha), broad silicate emission feature (HR5999) and the infrared emission bands (HD 97048, HD 97300, TY~CrA, HD 176386). The spectrum of HD179218 shows both silicate emission and infrared emission bands (IEB). All stars of our sample where the spectrum is entirely dominated by IEB have an extended emission on scales of a few thousand AU ($\sim 10''$). We verify the derived source extension found with ISOCAM by multi--aperture photometry with ISOPHT and compare our ISOCAM spectral photometry with ISOSWS spectra.
Far infrared observations of pre-protostellar sources in Lynds 183
K. Lehtinen,K. Mattila,D. Lemke,M. Juvela,T. Prusti,R. Laureijs
Physics , 2002, DOI: 10.1051/0004-6361:20021411
Abstract: Using ISOPHOT maps at 100 and 200um and raster scans at 100, 120, 150 and 200um we have detected four unresolved far-infrared sources in the high latitude molecular cloud L183. Two of the sources are identified with 1.3mm continuum sources found by Ward-Thompson et al. and are located near the temperature minimum and the coincident column density maximum of dust distribution. For these two sources, the ISO observations have enabled us to derive temperatures (about 8.3 K) and masses (about 1.4 and 2.4 solar masses). They are found to have masses greater than or comparable to their virial masses and are thus expected to undergo gravitational collapse. We classify them as pre-protostellar sources. The two new sources are good candidates for pre-protostellar sources or protostars within L183.
Identification of new transitional disk candidates in Lupus with Herschel
I. Bustamante,B. Merín,á. Ribas,H. Bouy,T. Prusti,G. L. Pilbratt,Ph. André
Physics , 2015, DOI: 10.1051/0004-6361/201424073
Abstract: New data from the Herschel Space Observatory are broadening our understanding of the physics and evolution of the outer regions of protoplanetary disks in star forming regions. In particular they prove to be useful to identify transitional disk candidates. The goals of this work are to complement the detections of disks and the identification of transitional disk candidates in the Lupus clouds with data from the Herschel Gould Belt Survey. We extracted photometry at 70, 100, 160, 250, 350 and 500 $\mu$m of all spectroscopically confirmed Class II members previously identified in the Lupus regions and analyzed their updated spectral energy distributions. We have detected 34 young disks in Lupus in at least one Herschel band, from an initial sample of 123 known members in the observed fields. Using the criteria defined in Ribas et al. (2013) we have identified five transitional disk candidates in the region. Three of them are new to the literature. Their PACS-70 $\mu$m fluxes are systematically higher than those of normal T Tauri stars in the same associations, as already found in T Cha and in the transitional disks in the Chamaeleon molecular cloud. Herschel efficiently complements mid-infrared surveys for identifying transitional disk candidates and confirms that these objects seem to have substantially different outer disks than the T Tauri stars in the same molecular clouds.
Far-infrared and molecular line observations of Lynds 183 - studies of cold gas and dust
M. Juvela,K. Mattila,K. Lehtinen,D. Lemke,R. Laureijs,T. Prusti
Physics , 2001, DOI: 10.1051/0004-6361:20011539
Abstract: We have mapped the dark cloud L183 in the far-infrared at 100um and 200um with the ISOPHOT photometer aboard the ISO satellite. The observations make it possible for the first time to study the properties of the large dust grains in L183 without confusion from smaller grains. The observations show clear colour temperature variations which are likely to be caused by changes in the emission properties of the dust particles. In the cloud core the far-infrared colour temperature drops below 12K. The data allow a new determination of the cloud mass and the mass distribution. The mass within a radius of 10 arcmin from the cloud centre is 25 Msun. We have mapped the cloud in several molecular lines including DCO+(2-1) and H13CO+(1-0). These species are believed to be tracers of cold and dense molecular material and we detect a strong anticorrelation between the DCO+ emission and the dust colour temperatures. In particular, the DCO+(2-1) emission is not detected towards the maximum of the 100um emission where the colour temperature rises above 15K. The H13CO+ emission follows the DCO+ distribution but CO isotopes show strong emission even towards the 100um peak. A comparison of the DCO+ and C18O maps shows sharp variations in the relative intensities of the species. Morphologically the 200um dust emission traces the distribution of dense molecular material as seen e.g. in C18O lines. A comparison with dust column density shows that C18O is depleted by a factor of 1.5 in the cloud core. We present results of R- and B-band starcounts. The extinction is much better correlated with the 200um than with the 100um emission. Based on the 200um correlation at low extinction values we deduce a value of ~17mag for the visual extinction towards the cloud centre.
Regeneration of Plantlet of Water Yam (Dioscorea oppositifoliaaL.) through In Vitro Culture from Nodal Segments
Kambaska Kumar BEHERA,Santilata SAHOO,Aratibala PRUSTI
Notulae Botanicae Horti Agrobotanici Cluj-Napoca , 2009,
Abstract: The present investigation was carried out with a view to regenerate plantlet of Dioscorea oppositifolia L through in vitro culture. Nodal vine segments from 45days old plants of field grown Dioscorea opositifolia were used as explants for initial culture. The explants were cultured on MS (Murashige and Skoog’s, 1962) medium supplemented with different concentration and combination of cytokinines and auxines for primary shoot proliferation. The best shoot proliferation was observed in MS medium containing 2.0 mg-l KINETIN +1.0 mg-l BAP+0.5mg-l NAA + 100mg-l ascorbic acid where 90 % of explants showed proliferation with highest rate of shoot multiplication (10.5 shoots per explant). For rooting, the in vitro micro shootlets were inoculated on to the half-strength MS basal media supplemented with 2.0 mg/l NAA and rooting was more profuse with micro tubers in the base of the root primordia. Rooted shoots were transplanted in the green house for hardening and their survival rate was 90 % in the field condition.
The dusty environment of HD 97300 as seen by Herschel and Spitzer
á. Kóspál,T. Prusti,N. L. J. Cox,G. L. Pilbratt,Ph. André,C. Alves de Oliveira,E. Winston,B. Merín,A. Ribas,P. Royer,R. Vavrek,C. Waelkens
Physics , 2012, DOI: 10.1051/0004-6361/201218823
Abstract: Aims. We analyze the surroundings of HD 97300, one of two intermediate-mass stars in the Chamaeleon I star-forming region. The star is known to be surrounded by a conspicuous ring of polycyclic aromatic hydrocarbons (PAHs). Methods. We present infrared images taken with Herschel and Spitzer using 11 different broad-band filters between 3.6 um and 500 um. We compare the morphology of the emission using cuts along different position angles. We construct spectral energy distributions, which we compare to different dust models, and calculate dust temperatures. We also derive opacity maps and analyze the density structure of the environment of HD 97300. Results. We find that HD 97300 has no infrared excess at or below 24 um, confirming its zero-age main-sequence nature. The morphology of the ring is very similar between 3.6 um and 24 um. The emission at these wavelengths is dominated by either PAH features or PAH continuum. At longer wavelengths, only the northwestern part of the ring is visible. A fit to the 100-500 um observations suggests that the emission is due to relatively warm (~26 K) dust. The temperature gradually decreases with increasing distance from the ring. We find a general decrease in the density from north to south, and an approximate 10% density increase in the northeastern part of the ring. Conclusions. Our results are consistent with the theory that the ring around HD 97300 is essentially a bubble blown into the surrounding interstellar matter and heated by the star.
The Herschel Gould Belt Survey in Chamaeleon II - Properties of cold dust in disks around young stellar objects
L. Spezzi,N. L. J. Cox,T. Prusti,B. Merin,A. Ribas,C. Alves de Oliveira,E. Winston,A. Kospal,P. Royer,R. Vavrek,Ph. Andre,G. L. Pilbratt,L. Testi,E. Bressert,L. Ricci,A. Menshchikov,V. Konyves
Physics , 2013, DOI: 10.1051/0004-6361/201321444
Abstract: We report on the Herschel Gould Belt survey (HGBS) of ChaII, focusing on the detection of Class I to III young stellar objects (YSOs). We aim at characterizing the circumstellar material around these YSOs and understanding which disk parameters are most likely constrained by the new HGBS data. We recovered 29 out of the 63 known YSOs in ChaII with a detection in at least one of the PACS/SPIRE pass-bands: 3 Class I YSOs (i.e.,100%), 1 Flat source (i.e., 50%), 21 Class II objects (i.e., 55%), 3 Class III objects (i.e, 16%) and the unclassified source IRAS 12522-7640. We explore PACS/SPIRE colors of this sample and present modeling of their SEDs using the RADMC-2D radiative transfer code. We find that YSO colors are confined in specific regions of PACS/SPIRE color-color diagrams. These color ranges are expected to be only marginally contaminated by extragalactic sources and field stars and, hence, provide a useful YSO selection tool when applied altogether. We were able to model the SED of 26 out of the 29 detected YSOs. We discuss the degeneracy/limitations of our SED fitting results and adopt the Bayesian method to estimate the probability of different values for the derived disk parameters. The Cha II YSOs present typical disk inner radii around 0.1 AU. The lower limit to Rc is typically around 50 AU. The lower limits to Mdisk are proportional to the stellar masses with a typical 0.3% ratio, i.e., in the range estimated in the literature for young Class II stars and brown dwarfs across a broad range of stellar masses. The estimated flaring angles, although very uncertain, point towards rather flat disks (1+phi less than 1.2), as found for low-mass M-type YSO samples in other star forming regions. Thus, our results support the idea that disk properties show a dependence on stellar properties.
ISO-SWS observations of interstellar solid 13CO2: heated ice and the Galactic 12C/13C abundance ratio
A. C. A. Boogert,P. Ehrenfreund,P. A. Gerakines,A. G. G. M. Tielens,D. C. B. Whittet,W. A. Schutte,E. F. van Dishoeck,Th. de Graauw,L. Decin,T. Prusti
Physics , 1999,
Abstract: We present observations of the stretching mode of 13CO2 ice along 13 lines of sight in the Galaxy, using the Short Wavelength Spectrometer on board of the Infrared Space Observatory. Remarkable variations are seen in the absorption band profile in the different lines of sight. The main feature is attributed to 13CO2 mixed with polar molecules such as H2O, and CH3OH. Several high-mass protostars show an additional narrow substructure at 4.382 um, which we attribute to a polar CO2 ice, that experienced heating. This heating effect is sustained by a good correlation of the strength of the substructure with dust and CO gas temperatures along the line of sight, and anti-correlation with ice abundances. Thus, our main conclusion is that interstellar CO2 ices around luminous protostars are subjected to, and altered by, thermal processing and that it may reflect the evolutionary stage of the nearby protostar. In contrast, the ices around low mass protostars and in a quiescent cloud in our sample do not show signs of thermal processing. Furthermore, we determine for the first time the Galactic 12C/13C ratio from the solid state. The 12CO2/13CO2 ratio for the local ISM (69+/-15), as well as the dependence on Galacto-centric radius, are in good agreement with gas phase (C18O, H2CO) studies. For the few individual objects for which gas phase values are available, the 12C/13C ratios derived from CO2 tend to be higher compared to CO studies (albeit with 2.5 sigma significance only). We discuss the implications of this possible difference for the chemical origin of interstellar CO2.
Identification of transitional disks in Chamaeleon with Herschel
á. Ribas,B. Merín,H. Bouy,C. Alves de Oliveira,D. R. Ardila,E. Puga,á. Kóspál,L. Spezzi,N. L. J. Cox,T. Prusti,G. L. Pilbratt,Ph. André,L. Matrà,R. Vavrek
Physics , 2013, DOI: 10.1051/0004-6361/201220960
Abstract: Transitional disks are circumstellar disks with inner holes that in some cases are produced by planets and/or substellar companions in these systems. For this reason, these disks are extremely important for the study of planetary system formation. The Herschel Space Observatory provides an unique opportunity for studying the outer regions of protoplanetary disks. In this work we update previous knowledge on the transitional disks in the Chamaeleon I and II regions with data from the Herschel Gould Belt Survey. We propose a new method for transitional disk classification based on the WISE 12 micron-PACS 70 micron color, together with inspection of the Herschel images. We applied this method to the population of Class II sources in the Chamaeleon region and studied the spectral energy distributions of the transitional disks in the sample. We also built the median spectral energy distribution of Class II objects in these regions for comparison with transitional disks. The proposed method allows a clear separation of the known transitional disks from the Class II sources. We find 6 transitional disks, all previously known, and identify 5 objects previously thought to be transitional as possibly non-transitional. We find higher fluxes at the PACS wavelengths in the sample of transitional disks than those of Class II objects. We show the Herschel 70 micron band to be an efficient tool for transitional disk identification. The sensitivity and spatial resolution of Herschel reveals a significant contamination level among the previously identified transitional disk candidates for the two regions, which calls for a revision of previous samples of transitional disks in other regions. The systematic excess found at the PACS bands could be a result of the mechanism that produces the transitional phase, or an indication of different evolutionary paths for transitional disks and Class II sources.
A new Herschel view of the young star T54: not a transitional disk?
L. Matrà,B. Merín,C. Alves de Oliveira,N. Huélamo,A. Kóspál,N. L. J. Cox,á. Ribas,E. Puga,R. Vavrek,P. Royer,T. Prusti,G. L. Pilbratt,P. André
Physics , 2012, DOI: 10.1051/0004-6361/201220461
Abstract: Context: Observations of transitional disks give us an understanding of the formation of planets and planetary systems such as our own. But care must be taken in the identification of such sources: the higher spatial resolution of the Herschel Space Observatory provides a new view on the origin of the far-infrared and sub-millimeter excesses observed. Aims: We review the nature of previously known transitional disks in the Chamaeleon I star-forming region with Herschel data. Methods: We analyze Herschel PACS and SPIRE images of the young star T54 together with ancillary images. We also analyze its spectral energy distribution and indications from optical and mid-infrared spectroscopy. Results: We detect extended emission in the PACS 70 \mu m image ~6" off source at a position angle of 196{\deg} from T54. The emission detected at longer wavelength (PACS 100, 160, SPIRE 250 and 350 \mu m) is also offset from the position of the star. This suggests that the excess observed in the far-infrared part of the SED is not fully associated with T54. Conclusions: Herschel images show that the far-infrared excess seen in T54 is not due to a transitional disk but to extended emission south-west of the source. The object still shows point-like and now downscaled excess at mid-infrared wavelengths, but its origin cannot be constrained without higher spatial resolution data. However, different indications point towards an evolved disk or extended unresolved emission close to the source.
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