HARD X-RAY EMISSION IN THE STAR-FORMING REGION ON 2: DISCOVERY WITH XMM-NEWTON

Journal Article · Thu Apr 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/712/2/763· OSTI ID:21394214

Oskinova, L M; Hamann, W -R; Feldmeier, A ^[1]; Gruendl, R A; Chu, Y -H ^[2]; Ignace, R ^[3]

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1. Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam (Germany)
2. Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)
3. Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614 (United States)

We obtained X-ray XMM-Newton observations of the open cluster Berkeley 87 and the massive star-forming region (SFR) ON 2. In addition, archival infrared Spitzer Space Telescope observations were used to study the morphology of ON 2, to uncover young stellar objects, and to investigate their relationship with the X-ray sources. It is likely that the SFR ON 2 and Berkeley 87 are at the same distance, 1.23 kpc, and hence are associated. The XMM-Newton observations detected X-rays from massive stars in Berkeley 87 as well as diffuse emission from the SFR ON 2. The two patches of diffuse X-ray emission are encompassed in the shell-like H II region GAL 75.84+0.40 in the northern part of ON 2 and in the ON 2S region in the southern part of ON 2. The diffuse emission from GAL 75.84+0.40 suffers an absorption column equivalent to A{sub V} {approx} 28 mag. Its spectrum can be fitted either with a thermal plasma model at T {approx}> 30 MK or by an absorbed power-law model with gamma {approx} -2.6. The X-ray luminosity of GAL 75.84+0.40 is L{sub X} {approx} 6 x 10{sup 31} erg s{sup -1}. The diffuse emission from ON 2S is adjacent to the ultra-compact H II (UCH II) region Cygnus 2N, but does not coincide with it or with any other known UCH II region. It has a luminosity of L{sub X} {approx} 4 x 10{sup 31} erg s{sup -1}. The spectrum can be fitted with an absorbed power-law model with gamma {approx} -1.4. We adopt the view of Turner and Forbes that the SFR ON 2 is physically associated with the massive star cluster Berkeley 87 hosting the WO-type star WR 142. We discuss different explanations for the apparently diffuse X-ray emission in these SFRs. These include synchrotron radiation, invoked by the co-existence of strongly shocked stellar winds and turbulent magnetic fields in the star-forming complex, cluster wind emission, or an unresolved population of discrete sources.

• OSTI ID: 21394214
• Journal Information: Astrophysical Journal, Vol. 712, Issue 2; Other Information: DOI: 10.1088/0004-637X/712/2/763; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
HARD X RADIATION
LUMINOSITY
MAGNETIC FIELDS
PHOTON EMISSION
SPECTRA
STAR CLUSTERS
STARS
STELLAR WINDS
SYNCHROTRON RADIATION
TELESCOPES
X-RAY SOURCES
BREMSSTRAHLUNG
ELECTROMAGNETIC RADIATION
EMISSION
IONIZING RADIATIONS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATION SOURCES
RADIATIONS
SORPTION
STELLAR ACTIVITY
X RADIATION