A VLBA Survey of radio stars in the Orion Nebula Cluster: I. The nonthermal radio population

Jan Forbrich; Sergio A. Dzib; Mark J. Reid; Karl M. Menten

doi:10.3847/1538-4357/abc68e

A VLBA Survey of radio stars in the Orion Nebula Cluster: I. The nonthermal radio population

Jan Forbrich, Sergio A. Dzib, Mark J. Reid, Karl M. Menten

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Abstract

We present first results of a four-epoch VLBA survey for nonthermal emission toward all 556 compact radio sources previously identified in a deep VLA survey of the Orion Nebula Cluster (ONC). We identify VLBA counterparts toward an unprecedented 123 sources. Of these, 41 do not have X-ray counterparts, of which 34 also do not display near-infrared counterparts. Since these cannot be explained by extragalactic background sources, this suggests a component of the ONC population of young stellar objects that are too deeply embedded for even X-rays to be detectable. We find pervasive variability and detect even most of the highest-S/N sources in only one out of four epochs. Neither a negative spectral index nor extreme variability in the VLA data is a good predictor of a VLBA detection.

Original language	English
Article number	23
Journal	The Astrophysical Journal
Volume	906
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/abc68e
Publication status	Published - 4 Jan 2021

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10.3847/1538-4357/abc68e

2011.09329v1
© 2020. The American Astronomical Society. All rights reserved.
Accepted author manuscript, 189 KBLicence: Other

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title = "A VLBA Survey of radio stars in the Orion Nebula Cluster: I. The nonthermal radio population",

abstract = "We present first results of a four-epoch VLBA survey for nonthermal emission toward all 556 compact radio sources previously identified in a deep VLA survey of the Orion Nebula Cluster (ONC). We identify VLBA counterparts toward an unprecedented 123 sources. Of these, 41 do not have X-ray counterparts, of which 34 also do not display near-infrared counterparts. Since these cannot be explained by extragalactic background sources, this suggests a component of the ONC population of young stellar objects that are too deeply embedded for even X-rays to be detectable. We find pervasive variability and detect even most of the highest-S/N sources in only one out of four epochs. Neither a negative spectral index nor extreme variability in the VLA data is a good predictor of a VLBA detection. ",

author = "Jan Forbrich and Dzib, {Sergio A.} and Reid, {Mark J.} and Menten, {Karl M.}",

note = "Funding Information: We thank the anonymous referee for helpful and constructive comments that lead to an improved presentation of our results. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Publisher Copyright: {\textcopyright} 2021. The American Astronomical Society.",

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AU - Reid, Mark J.

AU - Menten, Karl M.

N1 - Funding Information: We thank the anonymous referee for helpful and constructive comments that lead to an improved presentation of our results. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Publisher Copyright: © 2021. The American Astronomical Society.

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N2 - We present first results of a four-epoch VLBA survey for nonthermal emission toward all 556 compact radio sources previously identified in a deep VLA survey of the Orion Nebula Cluster (ONC). We identify VLBA counterparts toward an unprecedented 123 sources. Of these, 41 do not have X-ray counterparts, of which 34 also do not display near-infrared counterparts. Since these cannot be explained by extragalactic background sources, this suggests a component of the ONC population of young stellar objects that are too deeply embedded for even X-rays to be detectable. We find pervasive variability and detect even most of the highest-S/N sources in only one out of four epochs. Neither a negative spectral index nor extreme variability in the VLA data is a good predictor of a VLBA detection.

AB - We present first results of a four-epoch VLBA survey for nonthermal emission toward all 556 compact radio sources previously identified in a deep VLA survey of the Orion Nebula Cluster (ONC). We identify VLBA counterparts toward an unprecedented 123 sources. Of these, 41 do not have X-ray counterparts, of which 34 also do not display near-infrared counterparts. Since these cannot be explained by extragalactic background sources, this suggests a component of the ONC population of young stellar objects that are too deeply embedded for even X-rays to be detectable. We find pervasive variability and detect even most of the highest-S/N sources in only one out of four epochs. Neither a negative spectral index nor extreme variability in the VLA data is a good predictor of a VLBA detection.

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A VLBA Survey of radio stars in the Orion Nebula Cluster: I. The nonthermal radio population

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