scholarly journals Rotational Velocities and Radii of Pre–Main-Sequence Stars in the Orion Nebula Cluster

2001 ◽  
Vol 122 (6) ◽  
pp. 3258-3279 ◽  
Author(s):  
Katherine L. Rhode ◽  
William Herbst ◽  
Robert D. Mathieu
Keyword(s):  
Main Sequence ◽  
Orion Nebula ◽  
Main Sequence Stars

scholarly journals X-Ray Properties of Pre-Main-Sequence Stars in the Orion Nebula Cluster with Known Rotation Periods

2004 ◽  
Vol 127 (6) ◽  
pp. 3537-3552 ◽  
Author(s):  
Keivan G. Stassun ◽  
David R. Ardila ◽  
Mary Barsony ◽  
Gibor Basri ◽  
Robert D. Mathieu
Keyword(s):  
Main Sequence ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
X Ray ◽  
Rotation Periods

The Rotation Period Distribution of Pre–Main-Sequence Stars in and around the Orion Nebula

1999 ◽  
Vol 117 (6) ◽  
pp. 2941-2979 ◽  
Author(s):  
Keivan G. Stassun ◽  
Robert D. Mathieu ◽  
Tsevi Mazeh ◽  
Frederick J. Vrba
Keyword(s):  
Main Sequence ◽  
Rotation Period ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Period Distribution

scholarly journals Chemical Abundances in Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 215-224 ◽  
Author(s):  
Manuel Peimbert
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Type Ii ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Chemical Abundances ◽  
Element Abundances ◽  
Oxygen Gradient ◽  
The Galaxy ◽  
Halo Population

PN can be divided into four types depending on their chemical composition. In order of decreasing heavy element abundances the types are: I) He and N rich, II) intermediate population, III) high velocity, and IV) halo population. The type II PN are overabundant in N and C relative to the Orion Nebula. Well defined gradients across the galactic disk of He, N and O are derived from type II PN; the oxygen gradient is similar to the metallicity gradient derived from GK giants and F main sequence stars. By comparing the O, Ne and S abundances of PN of types III and IV with the Fe abundances of stars of similar population it is found that the O, Ne and S enrichment in the Galaxy probably took place before the Fe enrichment.

scholarly journals Magnetic Activity of Pre-main Sequence Stars

2004 ◽  
Vol 219 ◽  
pp. 211-222
Author(s):  
Eric D. Feigelson
Keyword(s):  
Main Sequence ◽  
Magnetic Activity ◽  
T Tauri Stars ◽  
X Rays ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Nearby Star ◽  
X Ray ◽  
T Tauri ◽  
Pms Stars

I review here recent advances in our understanding of magnetic activity in pre-main sequence (PMS) protostars and T Tauri stars. Results are based on recent imaging, spectroscopic and temporal studies of nearby star forming regions from the Chandra X — ray Observatory and XMM — Newton, including a first look at an ultradeep Chandra exposure of the Orion Nebula Cluster.Pre-main sequence stars exhibit a high level of X-ray emission dominated by a bewildering variety of magnetic reconnection flares. Activity is linked to bulk stellar properties — Lbol, mass, surface area or volume — rather than rotation. This suggests that dynamo processes in deeply convective PMS stars may fundamentally differ from the tachocline dynamo operating in main sequence stars.X-rays and MeV particles from magnetic flares will affect the circumstellar environment in PMS systems, particularly the protoplanetary disk. X-ray emission may influence: disk ionization, turbulence and viscosity; Jovian planet formation and migration; the production of meteoritic isotopes and melting of meteoritic chondrules; the heating and chemistry of the disk. X-ray surveys are also effective in locating post-T Tauri stars for disk evolution studies.

scholarly journals Herbig-Haro Objects in the Orion Nebula Region

1997 ◽  
Vol 182 ◽  
pp. 39-46
Author(s):  
C. R. O'Dell
Keyword(s):  
Molecular Cloud ◽  
Main Sequence ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
The South ◽  
The North ◽  
Giant Molecular Cloud ◽  
Hh Objects

The Orion Nebula Region has two different systems of objects classified as HH objects. The North System is associated with the H2 fingers seen in the infrared and is probably the result of Rayleigh-Taylor instabilities in shocked material moving into the near side of the giant molecular cloud OMC-1. The South System is associated with source(s) within the Trapezium cluster, with the shocked HH objects occuring where jets from pre-main sequence stars impinge on the neutral lid of material that lies across the front of the Orion Nebula. Such jets are different from those driving other HH objects in that these are passing through photoionized material and two of the Orion jets may have been detected.

scholarly journals X‐Rays in the Orion Nebula Cluster: Constraints on the Origins of Magnetic Activity in Pre–Main‐Sequence Stars

2003 ◽  
Vol 584 (2) ◽  
pp. 911-930 ◽  
Author(s):  
Eric D. Feigelson ◽  
James A. Gaffney III ◽  
Gordon Garmire ◽  
Lynne A. Hillenbrand ◽  
Leisa Townsley
Keyword(s):  
Main Sequence ◽  
Magnetic Activity ◽  
X Rays ◽  
Orion Nebula ◽  
Main Sequence Stars

scholarly journals Gaia stellar kinematics in the head of the Orion A cloud: runaway stellar groups and gravitational infall

2019 ◽  
Vol 487 (3) ◽  
pp. 2977-3000 ◽  
Author(s):  
K V Getman ◽  
E D Feigelson ◽  
M A Kuhn ◽  
G P Garmire
Keyword(s):  
Main Sequence ◽  
Theoretical Models ◽  
Small Scale ◽  
Orion Nebula ◽  
Proper Motions ◽  
Stellar Kinematics ◽  
Main Sequence Stars ◽  
Stellar Feedback ◽  
Kinematic Studies ◽  
Stellar Kinematic

ABSTRACT This work extends previous kinematic studies of young stars in the head of the Orion A cloud (OMC-1/2/3/4/5). It is based on large samples of infrared, optical, and X-ray selected pre-main-sequence stars with reliable radial velocities and Gaia-derived parallaxes and proper motions. Stellar kinematic groups are identified assuming they mimic the motion of their parental gas. Several groups are found to have peculiar kinematics: the NGC 1977 cluster and two stellar groups in the extended Orion nebula (EON) cavity are caught in the act of departing their birthplaces. The abnormal motion of NGC 1977 may have been caused by a global hierarchical cloud collapse, feedback by massive Ori OB1ab stars, supersonic turbulence, cloud–cloud collision, and/or slingshot effect; the former two models are favoured by us. EON groups might have inherited anomalous motions of their parental cloudlets due to small-scale ‘rocket effects’ from nearby OB stars. We also identify sparse stellar groups to the east and west of Orion A that are drifting from the central region, possibly a slowly expanding halo of the Orion nebula cluster. We confirm previously reported findings of varying line-of-sight distances to different parts of the cloud’s Head with associated differences in gas velocity. 3D movies of star kinematics show contraction of the groups of stars in OMC-1 and global contraction of OMC-123 stars. Overall, the head of Orion A region exhibits complex motions consistent with theoretical models involving hierarchical gravitational collapse in (possibly turbulent) clouds with OB stellar feedback.

scholarly journals Far-ultraviolet intensities of Orion stars

1970 ◽  
Vol 36 ◽  
pp. 100-108
Author(s):  
George R. Carruthers
Keyword(s):  
Wavelength Range ◽  
Main Sequence ◽  
Photometric Data ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Spectral Class ◽  
Color Excess ◽  
Far Ultraviolet ◽  
Spectral Intensities ◽  
Good Agreement

Photometric data in the 1050–1180 Å and 1230–1350 Å wavelength ranges, and electronographic spectra in the 1000–1600 Å wavelength range, were obtained in an Aerobee rocket flight on January 30, 1969. The spectral intensities derived from these data for main-sequence stars are in good agreement with the model atmospheres of Morton and co-workers. Giant and supergiant stars, however, appear to be up to one magnitude weaker, at 1115 Å, than main-sequence stars of the same spectral class.The correction for interstellar reddening appears to be not inconsistent with a 1/λ extrapolation of earlier determinations of Smith (1967) and Stecher (1965), except in the case of θ Ori, in which the predicted color excess appears to be much too great, confirming the existence of a peculiar reddening law in the Orion Nebula region.

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

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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