Far-infrared observations of main sequence stars surrounded by dust shells

Intermediate mass (2 < M/M⊙ < 9) pre-main sequence objects, also named Herbig Ae/Be stars, are known to have excess radiation in the near-infrared. From IRAS o bservations it turns out without doubt (quality 3, high S/N radio), that these objects are very strong far-infrared emitters at 12, 25, 60 and often also at 100 μm. The spectral energy distribution, depicted in Fig. 1 for intermediate mass pre-main sequence stars, show clearly this large excess. From the difference curves it is apparent that this excess radiation is most probably caused by several dust shells. Using very simplified methods it is possible to derive the average temperature of the dust shells (see Thé, Wesselius, Tjin A Djie and Steenman, 1986). If the chemical composition of the mixture of the dust grains and their average size are assumed it is also possible to estimate other characteristics like the distance from the central star and the mass of the dust shells (see Thé, Hageman, Westerlund, Tjin A Djie, 1985).

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VISION – Vienna survey in Orion

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832577 ◽

2019 ◽

Vol 622 ◽

pp. A149 ◽

Cited By ~ 14

Author(s):

Josefa Elisabeth Großschedl ◽

João Alves ◽

Paula S. Teixeira ◽

Hervé Bouy ◽

Jan Forbrich ◽

...

Keyword(s):

Main Sequence ◽

Near Infrared ◽

Far Infrared ◽

Circumstellar Disks ◽

Mass Star ◽

Main Sequence Stars ◽

Star Forming ◽

Spatial Coverage ◽

Significant Difference ◽

Infrared Data

We have extended and refined the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3 deg2, ∼950 pc2), seeing limited resolution (∼0.7″), and sensitivity (Ks < 19 mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ∼6.4% and ∼2.3%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A’s low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2980 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 185 flat-spectrum sources, and 2607 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.

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Far-infrared photometry of low-mass pre-main-sequence stars with broad CO wings

The Astrophysical Journal ◽

10.1086/163954 ◽

1986 ◽

Vol 301 ◽

pp. 894 ◽

Cited By ~ 10

Author(s):

N. J., II Evans ◽

R. M. Levreault ◽

P. M. Harvey

Keyword(s):

Main Sequence ◽

Far Infrared ◽

Infrared Photometry ◽

Main Sequence Stars ◽

Low Mass

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Infrared observations of GGD objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900156190 ◽

1987 ◽

Vol 122 ◽

pp. 125-126

Author(s):

R. Carballo ◽

C. Eiroa ◽

A. Mampaso

Keyword(s):

Main Sequence ◽

Near Infrared ◽

Far Infrared ◽

Infrared Emission ◽

Be Stars ◽

Main Sequence Stars ◽

Infrared Excess ◽

Dark Clouds ◽

Infrared Sources ◽

Different Characteristics

We present accurate positions and near infrared photometry (Table I) of 11 point-like objects in the neighbourhood of GGD objects obtained on the 1.55 m and on the 1.23 m in Teide Obs. and Calar Alto Obs. respectively, in Spain. Several of the near infrared sources are directly associated with the GGD nebulae and/or are candidate for their excitation. In addition some of them seem to be the near infrared counterparts of IRAS sources. We believe, on the basis of their infrared excess, far infrared emission (IRAS), association with nebulosity, coincidence with H2O masers or the fact that in most cases the observed luminosities are higher than those expected for main sequence stars, that most of them (9/12) are young stars embedded in the dark clouds which contain the GGD objects. The loci of the detected sources in an (H-K,K-L) infrared two-colour diagram is the same as that obtained for known pre-main sequence stars, such as T Tauris and Herbig Ae-Be stars, indicating the presence of dust shells with temperatures in the range 800–1500 K. The observed range in luminosity, 10–4600 L⊙, added to other different characteristics found between them, such' as the presence, or absence, of H2O masers, indicates the interest for a detailed study of the infrared sources and related GGD nebulae.

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Distribution of Dust in the Disk Around Beta Pictoris

International Astronomical Union Colloquium ◽

10.1017/s0252921100067221 ◽

1991 ◽

Vol 126 ◽

pp. 421-424

Author(s):

Takenori Nakano

Keyword(s):

Thermal Radiation ◽

Main Sequence ◽

Planet Formation ◽

Far Infrared ◽

Main Sequence Stars ◽

Circumstellar Material ◽

Stellar Radiation ◽

Beta Pictoris ◽

Infrared Astronomical Satellite ◽

Astronomical Satellite

Large far-infrared excesses in some nearby main-sequence stars, revealed by theInfrared Astronomical Satellite (IRAS), have been interpreted as being due to thermal radiation from dust orbiting the stars, heated to about 100K by the stellar radiation (Aumannet al.1984; Aumann 1985; Sadakane and Nishida 1986). The existence of solid circumstellar material is commonly interpreted in the context of planet formation, and the dust has been suggested to be formed by collisions of planetesimals (Nakano 1987, 1988).

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Chromospheric activity as a function of age in main-sequence stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900053146 ◽

1966 ◽

Vol 24 ◽

pp. 40-43

Author(s):

O. C. Wilson ◽

A. Skumanich

Keyword(s):

Main Sequence ◽

The Sun ◽

Main Sequence Stars ◽

Tentative Conclusion ◽

Chromospheric Activity ◽

General Field ◽

Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

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On The Radii of Ap Stars

International Astronomical Union Colloquium ◽

10.1017/s025292110008043x ◽

1976 ◽

Vol 32 ◽

pp. 49-55 ◽

Cited By ~ 1

Author(s):

F.A. Catalano ◽

G. Strazzulla

Keyword(s):

Observational Data ◽

Line Width ◽

Main Sequence ◽

Main Sequence Stars ◽

Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

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