X-Ray Emission From Young Stars in the Massive Star-Forming Region Iras 20126+4104

Abstract

We present a 40 ks Chandra observation of the IRAS 20126+4104 core region. In the inner 6 two X-ray sources were detected, which are coincident with the radio jet source I20S and the variable radio source I20Var. No X-ray emission was detected from the nearby massive protostar I20N. The spectra of both detected sources are hard and highly absorbed, with no emission below 3 keV. For I20S, the measured 0.5-8 keV count rate was 4.3 counts ks −1 . The X-ray spectrum was fitted with an absorbed 1T APEC model with an energy of kT = 10 keV and an absorbing column of N H = 1.2 × 10 23 cm −2 . An unabsorbed X-ray luminosity of about 1.4 × 10 32 erg s −1 was estimated. The spectrum shows broad line emission between 6.4 and 6.7 keV, indicative of emission from both neutral and highly ionized iron. The X-ray light curve indicates that I20S is marginally variable; however, no flare emission was observed. The variable radio source I20Var was detected with a count rate of 0.9 counts ks −1 but there was no evidence of X-ray variability. The best-fit spectral model is a 1T APEC model with an absorbing hydrogen column of N H = 1.1 × 10 23 cm −2 and a plasma energy of kT = 6.0 keV. The unabsorbed X-ray luminosity is about 3 × 10 31 erg s −1 .

The Massive Star-Forming Regions Omnibus X-Ray Catalog

“…W51 IRS2E is exceptional even compared to the other very young, embedded massive stars with hard X-ray emission that we have described in the MOXC sample; in order for its emission to be concentrated in this reprocessed fluorescent neutral Fe line, the ionizing source itself must be producing most of its high-energy photons above the Fe absorption edge at 7.1 keV. A similar source is found in the MSFR IRAS 20126+4104 (Anderson et al 2011). Figure 11(e) shows a bright X-ray source with a K < 10 2MASS counterpart, likely the mid-O-type massive star ionizing radio H ii region "g" (Mehringer 1994), called source #4168 in "Region 2" defined by Okumura et al (2000).…”

X-Ray and Radio Observations of the Massive Star-Forming Region Iras 20126+4104

“…43 (CXO J201426.2+411327.9, 33 counts). The latter two sources correspond to the radio sources I20S and I20var (Hofner et al 2007), respectively, and have recently been discussed by Anderson et al (2011).…”

“…Results for the two massive protostellar candidate sources I20S and I20var have recently been reported by Anderson et al (2011). We refer to this paper for a more detailed description of the observations and basic data reduction.…”

“…29, the position angle is PA = 64°. 3, and the rms noise is 6.5 μ Jy beam We used the WAVDETECT program in CIAO 6 version 3.4 to identify X-ray sources in the ACIS field of view (see Anderson et al 2011 for further details). The program MKPSFMAP was used to supply information on the PSF across the ACIS field of view to WAVDETECT, and an exposure map was applied to account for varying exposure time.…”

Evolution of Stellar Feedback in HII Regions

“…However, the high median energies of the counts (≈3-6 keV) and the elevated hardness ratios 3 (≈0.5-1.0) of the targets suggest that the spectra are quite hard. Previous X-ray studies of young H ii regions have also found that hard X-rays dominate their emission (e.g., Tsujimoto et al 2006;Anderson et al 2011), which may indicate very hot plasma temperatures (with kT X 6 keV) and/or extreme column densities (of N H 10 23 cm −2 ) that attenuate the soft X-rays.…”