<i>Chandra</i>X‐Ray Observation of the Orion Nebula Cluster. I. Detection, Identification, and Determination of X‐Ray Luminosities

Flaccomio, E.; Damiani, F.; Micela, G.; Sciortino, S.; Harnden, F. R.; Murray, S. S.; Wolk, S. J.

doi:10.1086/344535

Cited by 62 publications

(55 citation statements)

References 36 publications

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“…They detect a weak source (ID 428) with a total of 74 counts and classify it as long-term variable due to differences between the two observations (see also Garmire et al 2000, for the first of the two datasets). Flaccomio et al (2003) detect the source in Chandra HRC observations in 2000 February; they find 15 counts in a 63 ks exposure. Thus, in a total of 987 ks (i.e.…”

Section: X-ray Data: Archival Chandra Observationsmentioning

confidence: 97%

A 1.3 cm wavelength radio flare from a deeply embedded source in the Orion BN/KL region

Forbrich

Menten²,

Reid

2007

A&A

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Aims. Our aim was to measure and characterize the short-wavelength radio emission from young stellar objects (YSOs) in the Orion Nebula Cluster and the BN/KL star-forming region. Methods. We used the NRAO Very Large Array at a wavelength of λ = 1.3 cm and we studied archival X-ray, infrared, and radio data.Results. During our observation, a strong outburst (flux increasing >10 fold) occurred in one of the 16 sources detected at λ = 1.3 cm, while the others remained (nearly) constant. This source does not have an infrared counterpart, but has subsequently been observed to flare in X-rays. Curiously, a very weak variable double radio source was found at other epochs near this position, one of whose components is coincident with it. A very high extinction derived from modeling the X-ray emission and the absence of an infrared counterpart both suggest that this source is very deeply embedded.

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Section: X-ray Data: Archival Chandra Observationsmentioning

confidence: 97%

A 1.3 cm wavelength radio flare from a deeply embedded source in the Orion BN/KL region

Forbrich

Menten²,

Reid

2007

A&A

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“…Nevertheless, they are the most complete set of theoretical tracks available in the literature, and have already been used in recent studies of star formation regions (e.g. Flaccomio et al 2003).…”

Section: Masses Ages and Spatial Distributionmentioning

confidence: 99%

The star formation region NGC 6530: Distance, ages and initial mass function

Prisinzano

Damiani

Micela

et al. 2005

A&A

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Abstract. We present astrometry and BV I photometry, down to V 22, of the very young open cluster NGC 6530, obtained from observations taken with the Wide Field Imager camera at the MPG/ESO 2.2 m Telescope. Both the V vs. B − V and the V vs. V − I color−magnitude diagrams (CMD) show that the upper main sequence is dominated by very bright cluster stars, while, because of the high obscuration of the giant molecular cloud surrounding the cluster, the blue envelopes of the diagrams at V 14 are limited to the main sequence stars at the distance of NGC 6530. This particular structure of the NGC 6530 CMD allows us to conclude that its distance is about d 1250 pc, significantly lower than the previous determination of d = 1800 pc. We have positionally matched our optical catalog with the list of X-ray sources found in a Chandra-ACIS observation, finding a total of 828 common stars, 90% of which are pre-main sequence stars in NGC 6530. Using evolutionary tracks of Siess et al. (2000), mass and age values are inferred for these stars. The median age of the cluster is about 2.3 Myr; in the mass range (0.6−4.0) M , the Initial Mass Function (IMF) shows a power law index x = 1.22 ± 0.17, consistent with both the Salpeter index (1.35), and with the index derived for other young clusters; towards smaller masses the IMF shows a peak and then it starts to decrease.

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“…However, for most stars, with the possible exception of TW Hya (Kastner et al 2002;Dupree et al 2012), this cool plasma does not contribute significantly to the X-ray flux detected in the 0.3-10 keV energy band covered by present-day imaging detectors, such as those onboard of Chandra and XMM-Newton. In fact, in spite of this additional soft component, CTTS are, on average, two to three times fainter in X-rays compared to WTTSs of the same mass or L bol (Neuhaeuser et al 1995;Damiani et al 1995;Flaccomio et al 2003a;Preibisch et al 2005). Moreover, their activity levels at any given mass or L bol show a larger scatter (Preibisch et al 2005).…”

Section: Introductionmentioning

confidence: 99%

X-ray variability of pre-main-sequence stars

Flaccomio

Micela

Sciortino

2012

A&A

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Context. The first million years of the pre-main-sequence (PMS) evolution of low-mass stars are characterized by magnetospheric accretion, a circumstellar proto-planetary disk, and the processes leading to its dispersal. Among these, photo-evaporation caused by strong X-ray emission from the central star is probably significant. Several aspects of the X-ray emission from coronae and accretion shocks remain mysterious, e.g., whether and how much accretion affects coronal emission. Aims. We studied the X-ray variability of ∼1 Myr old low-mass PMS stars as a function of timescale, stellar rotation, and stellar characteristics to gain insights into the working of PMS coronae, their X-ray emission, and the circumstellar environment in which they are immersed. Methods. We have exploited the ∼850 ks long Chandra observation of the Orion Nebula Cluster obtained by the COUP collaboration in January 2003, and statistically analyzed the X-ray lightcurves of low-mass stars in several subsamples. Our main focus was to characterize the different X-ray behavior of stars with and without circumstellar accretion disks, and to infer the physical mechanism responsible for the observed variability. Results. Accreting stars (classical T Tauri stars, CTTSs) are found to be more variable than non-accreting stars (weak-line T Tauri stars, WTTSs) at all timescales and in all X-ray energy bands considered. Variability is seen to increase with timescale, up to the longest probed, ∼10 days. Signatures of rotational modulation are observed for both CTTSs and WTTSs, and most clearly for CTTSs in the soft X-ray band. Lower mass stars are more variable than higher mass stars. Conclusions. We propose that the difference in variability between CTTSs and WTTSs may be explained assuming that the X-ray emission of CTTS is affected by time-variable absorption due to circumstellar structures, such as warps in the inner disk and/or accretion streams. This suggestion is appealing because, in the hypothesis that the coronae of CTTSs and WTTSs are similar, it may also explain why CTTSs have lower and more scattered X-ray emission levels compared to WTTSs.

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ChandraX‐Ray Observation of the Orion Nebula Cluster. I. Detection, Identification, and Determination of X‐Ray Luminosities

Cited by 62 publications

References 36 publications

A 1.3 cm wavelength radio flare from a deeply embedded source in the Orion BN/KL region

A 1.3 cm wavelength radio flare from a deeply embedded source in the Orion BN/KL region

The star formation region NGC 6530: Distance, ages and initial mass function

X-ray variability of pre-main-sequence stars

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