Chamaeleon complex

The Chamaeleon complex is a large star forming region (SFR) that includes the Chamaeleon I, Chamaeleon II, and Chamaeleon III dark clouds. It occupies nearly all of the constellation Chamaeleon and overlaps into Apus, Musca, Carina and Octans. The mean density of X-ray sources is about one source per square degree.[2]

Star in the process of forming within the Chamaeleon cloud.[1]

Chamaeleon I dark cloud
This is a ROSAT false-color image in X-rays between 500 eV and 1.1 keV of the Chamaeleon I dark cloud. The contours are 100 µm emission from dust measured by the IRAS satellite. Credit: D Burrows, J Mendenhall, and E Feigelson Penn State University using the US/German ROSAT satellite.

The Chamaeleon I (Cha I) cloud is one of the nearest active star formation regions at ~160 pc.[3] It is relatively isolated from other star-forming clouds, so it is unlikely that older pre-main sequence (PMS) stars have drifted into the field.[3] The total stellar population is 200-300.[3] The Cha I cloud is further divided into the North cloud or region and South cloud or main cloud.

HD 97300 emits X-rays, illuminates the reflection nebula IC 2631 and is one of the highest mass members of the Cha I cloud, spectral type B9V, a Herbig Ae/Be star without emission lines.[3]

Cha Halpha 1 is an object of spectral type M8 in the Chamaeleon I dark cloud that was determined in 1998 to be an X-ray source and as such is the first X-ray emitting brown dwarf found.

There are some seventy to ninety X-ray sources in the Chamaeleon I star forming region.[4] The Uhuru X-ray source (4U 1119-77) is within the Chamaeleon I cloud. This source region within the Chamaeleon I dark cloud was observed by ROSAT on February 9 at 22:14:47 UTC to February 18, 1991, 17:59:12 UTC, and on March 6, 1991, from 09:12:19 to 13:05:13 UTC.[4] This cloud contains both "weak" T Tauri (WTT) stars and "classical" T Tauri (CTT) stars.[4] Chamaeleon I X-ray ROSAT source 66 is at RA 11h 17m 36.4-37.9s Dec -77° 04' 27-50", is a CTT, Chamaeleon I No. T56, aka CTT star HM 32.[4]

The Chamaeleon I dark cloud was observed with the Imaging Proportional Counter (IPC) on board the Einstein Observatory for 2.5 h on January 23–24, 1981, identifying some 22 X-ray sources.[5] None of these sources was closer than 8' to 4U 1119-77.

Chamaeleon II dark cloud

Chamaeleon II contains the Uhuru source 4U 1302-77. It is close to RXJ 1303.1-7706 at RA 13h 03m 04.70s Dec -77° 06' 55.0", a K7-M0 new WTT.[2] The Chamaeleon II dark cloud contains some 40 X-ray sources.[6] Observation in Chamaeleon II was carried out from September 10 to 17, 1993.[6] Source RXJ 1301.9-7706, a new WTTS candidate of spectral type K1, is closest to 4U 1302-77.[6]

Chamaeleon III dark cloud

"Chamaeleon III appears to be devoid of current star-formation activity."[7]

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References
  1. "A nursery for unruly young stars". ESA/Hubble Picture of the Week. Retrieved 4 February 2014.
  2. Alcala JM; Krautter J; Schmitt JHMM; Covino E; Wichmann R; Mundt R (Nov 1995). "A study of the Chamaeleon star forming region from the ROSAT all-sky survey. I. X-ray observations and optical identifications". Astron. Astrophys. 114 (11): 109–34. Bibcode:1995A&AS..114..109A.
  3. Feigelson ED, Lawson WA (Oct 2004). "An X-ray census of young stars in the Chamaeleon I North Cloud". Astrophys. J. 614 (10): 267–83. arXiv:astro-ph/0406529. Bibcode:2004ApJ...614..267F. doi:10.1086/423613.
  4. Feigelson ED, Casanova S, Montmerle T, Guibert J (Oct 1993). "ROSAT X-Ray Study of the Chamaeleon I Dark Cloud. I. The Stellar Population". Astrophys. J. 416 (10): 623–46. Bibcode:1993ApJ...416..623F. doi:10.1086/173264.
  5. Feigelson ED, Kriss GA (Mar 1989). "Soft X-ray observations of pre-main-sequence stars in the Chamaeleon dark cloud". Astrophys. J. 338 (3): 262–76. Bibcode:1989ApJ...338..262F. doi:10.1086/167196. hdl:2060/19880002197. S2CID 121939381.
  6. Alcalá JM; Covino E; Sterzik MF; Schmitt JHMM; Krautter J; Neuhäuser R (Mar 2000). "A ROSAT pointed observation of the Chamaeleon II dark cloud". Astron. Astrophys. 355 (3): 629–38. Bibcode:2000A&A...355..629A.
  7. Yamauchi S, Hamaguchi K, Koyama K, Murakami H (Oct 1998). "ASCA Observations of the Chamaeleon II Dark Cloud". Publ. Astron. Soc. Jpn. 50 (10): 465–74. Bibcode:1998PASJ...50..465Y. doi:10.1093/pasj/50.5.465.
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