X-ray emission from early-type stars in the Orion Nebula Cluster

The X-ray properties of twenty ~1 Myr old O, B, and A stars of the Orion Trapezium are examined with data from the Chandra Orion Ultradeep Project (COUP). On the basis of simple theories for X-ray emission, we define two classes separated at spectral type B4: hotter stars have strong winds that may give rise to X-ray emission in small- or large-scale wind shocks, and cooler stars that should be X-ray dark due to their weaker winds and absence of outer convection zones where dynamos can generate magnetic fields. Only two of the massive stars show exclusively the constant soft-spectrum emission... Mehr ...

Verfasser: Beate Stelzer
Salvatore Sciortino
Fabio Favata
Eric D. Feigelson
Ettore Flaccomio
Giuseppina Micela
Thomas Preibisch
Thierry Montmerle
Dokumenttyp: Artikel
Erscheinungsdatum: 2005
Schlagwörter: FORTHEM Alliance / NEANIAS Space Research Community / Netherlands / Space and Planetary Science / Astronomy and Astrophysics
Sprache: Englisch
Permalink: https://search.fid-benelux.de/Record/base-27591598
Datenquelle: BASE; Originalkatalog
Powered By: BASE
Link(s) : https://www.openaccessrepository.it/record/98991

The X-ray properties of twenty ~1 Myr old O, B, and A stars of the Orion Trapezium are examined with data from the Chandra Orion Ultradeep Project (COUP). On the basis of simple theories for X-ray emission, we define two classes separated at spectral type B4: hotter stars have strong winds that may give rise to X-ray emission in small- or large-scale wind shocks, and cooler stars that should be X-ray dark due to their weaker winds and absence of outer convection zones where dynamos can generate magnetic fields. Only two of the massive stars show exclusively the constant soft-spectrum emission expected from the standard model for X-ray emission from hot stars involving many small shocks in an unmagnetized radiatively accelerated wind. Most of the other massive O7-B3 stars exhibit some combination of soft-spectrum wind emission, hard-spectrum flaring, and/or rotational modulation indicating large-scale inhomogeneity, suggesting magnetic confinement of winds with large-scale shocks. Most of the stars in the weak-wind class exhibit X-ray flares and have luminosities that are consistent with magnetic activity from known or unseen low-mass companions. All non-detections belong to the weak-wind class.