Submillimeter lines from circumstellar disks around pre-main
sequence stars

AbstractThe Isaac Newton Photometric H-Alpha Survey (IPHAS) provides (r′-Hα)-(r′-i′) colors, which can be used to select AV0-5 Main Sequence star candidates (age~20-200 Myr). By combining a sample of 23050 IPHAS-selected A-type stars with 2MASS, GLIMPSE and MIPSGAL photometry we searched for mid-infrared excesses attributable to dusty circumstellar disks. Positional cross-correlation yielded a sample of 2692 A-type stars, of which 0.6% were found to have 8-μm excesses above the expected photospheric values. The low fraction of main sequence stars with mid-IR excesses found in this work indicates that dust disks in the terrestrial planet zone of Main Sequence intermediate mass stars are rare. Dissipation mechanisms such as photo-evaporation, grain growth, collisional grinding or planet formation could possibly explain the depletion of dust detected in the inner regions of these disks.

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Circumstellar Disks and Star Formation

Highlights of Astronomy ◽

10.1017/s1539299600009229 ◽

1992 ◽

Vol 9 ◽

pp. 377-380

Author(s):

L. Hartmann ◽

M. Gomez ◽

S.J. Kenyon

Keyword(s):

Star Formation ◽

Spectral Region ◽

Main Sequence ◽

Circumstellar Disks ◽

Central Star ◽

Disk Accretion ◽

Main Sequence Stars ◽

Excess Emission ◽

Infrared Spectral ◽

The Masses

Results from the IRAS satellite showed that many pre-main sequence stars exhibited unexpectedly large fluxes in the infrared spectral region. Several studies have shown that the simplest and most satisfying explanation of this excess emission is that it arises in optically-thick, dusty, circumstellar disks (Rucinski 1985; Adams, Lada, and Shu 1987, 1988; Kenyon and Hartmann 1987; Bertout, Basri, and Bouvier 1988; Basri and Bertout 1989). The masses of these disks are estimated to range between 10-3M⊙ to 1M⊙ (Beckwith et al. 1990; Adams et al. 1990), large enough that disk accretion may have a significant effect on the evolution of the central star. Indeed, Mercer-Smith, Cameron, and Epstein (1984) suggested that stars are essentially completely accreted from disks, rather than formed from quasi-spherical accretion (Stabler 1983, 1988).

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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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Bipolar flows and jets from stars of different spectral types: Observations

Symposium - International Astronomical Union ◽

10.1017/s0074180900155895 ◽

1987 ◽

Vol 122 ◽

pp. 39-50

Author(s):

Martin Cohen

Keyword(s):

Main Sequence ◽

Cataclysmic Variables ◽

Circumstellar Disks ◽

Red Giants ◽

Main Sequence Stars ◽

Hot Stars

The fact that bipolar flows are widespread among stars of very different spectral types is emphasized. First, the stars associated with the phenomenon are divided into broad types: protostars and pre-main-sequence stars; red giants; symbiotic objects; protoplanetaries; planetaries; novae and cataclysmic variables; and peculiar hot stars. Second, the evidence for circumstellar “disks” or toroids is considered among these different categories of star. Finally, the possible role of binarity is discussed.

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Molecular hydrogen in the circumstellar disks of pre-main sequence stars

EAS Publications Series ◽

10.1051/eas/1041011 ◽

2010 ◽

Vol 41 ◽

pp. 155-165 ◽

Cited By ~ 1

Author(s):

M. Deleuil ◽

J. C. Bouret ◽

P. Feldman ◽

A. Lecavelier des Etangs ◽

C. Martin-Zaidi ◽

...

Keyword(s):

Molecular Hydrogen ◽

Main Sequence ◽

Circumstellar Disks ◽

Main Sequence Stars

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High S/N Spectroscopy of Pre-Main Sequence Stars I

Symposium - International Astronomical Union ◽

10.1017/s0074180900034823 ◽

1988 ◽

Vol 132 ◽

pp. 87-93

Author(s):

I. Appenzeller

Keyword(s):

Magnetic Fields ◽

Main Sequence ◽

Circumstellar Disks ◽

Circumstellar Matter ◽

Spectroscopic Measurement ◽

Spectral Lines ◽

Stellar Winds ◽

Main Sequence Stars ◽

Pms Stars ◽

Very High

The spectra of PMS stars usually are superpositions of contributions from a relatively normal photosphere, an often strongly enhanced chromosphere, and of circumstellar matter related to stellar winds, accreation flows, jets, and cool circumstellar disks. Only high S/N data allows a reliable separation of these different contributions. Because of the high optical depths of PMS chromospheres, the PMS photospheres often can be observed in the very weak spectral lines only, which are undectable on low S/N spectrograms. Finally, magnetic fields are assumed to play a particularly important role for the appearance and evolution of PMS objects. Their spectroscopic measurement requires very high S/N data.

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Erratum: Submillimeter lines from circumstellar disks around pre-main sequence stars

Astronomy and Astrophysics ◽

10.1051/0004-6361:20011496 ◽

2001 ◽

Vol 379 (3) ◽

pp. 924-924 ◽

Cited By ~ 1

Author(s):

G.-J. van Zadelhoff ◽

E. F. van Dishoeck ◽

W.-F. Thi ◽

G. A. Blake

Keyword(s):

Main Sequence ◽

Circumstellar Disks ◽

Main Sequence Stars

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High-excitation molecular lines from circumstellar disks

Symposium - International Astronomical Union ◽

10.1017/s0074180900218330 ◽

2004 ◽

Vol 202 ◽

pp. 384-386

Author(s):

Gerd-Jan van Zadelhoff ◽

Ewine F. van Dishoeck ◽

Wing-Fai Thi ◽

Geoffrey A. Blake

Keyword(s):

Surface Layer ◽

Main Sequence ◽

Circumstellar Disks ◽

High Excitation ◽

Main Sequence Stars ◽

Set Constraints ◽

Density Distributions ◽

Lower Excitation ◽

Molecular Lines ◽

Low Mass

Observations of submillimeter lines of CO, HCO+, HCN and their isotopes from circumstellar disks around low-mass pre-main sequence stars can be used to set constraints on the temperature and density distributions in these disks. The lines considered here originate from levels with higher excitation temperatures and critical densities than studied before (CO 6–5, HCO+ and HCN 4–3), and are combined with interferometer data on lower excitation lines. We discuss the results for two disks, i.e., those around LkCa 15 and TW Hya. We find that the TW Hya disk has a warm surface layer and agrees well with a flaring disk geometry, while the LkCa 15 disk is cooler and can be described by either dust-settling in a flared disk or a flatter disk overall. The densities are well described by disk models in the literature.

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