A CHANDRA OBSERVATION OF THE TW HYDRAE ASSOCIATION BROWN DWARF 2MASSW J1139511-315921
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
- Department of Geology and Astronomy, West Chester University, West Chester, PA 19383 (United States)
We report on a sequence of Chandra X-Ray Observatory observations of the TW Hydrae brown dwarf (BD) 2MASSW J1139511-315921 (2M1139). In the combined 31 ks ACIS-S exposure, 2M1139 is detected at the 3{sigma} confidence level. We find an X-ray luminosity of L{sub X} = 1.4{sup +2.7}{sub -1.0} x 10{sup 26} erg s{sup -1} or log L{sub X}/L{sub bol} = -4.8 {+-} 0.3. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B): both have H{alpha} emission, both show no signatures of accretion, and both have comparable ages and spectral types. TWA 5B was previously detected in X-rays with a luminosity of L{sub X} = 4 x 10{sup 27} erg s{sup -1} or log L{sub X}/L{sub bol} = -3.4, an order of magnitude more luminous in X-rays than 2M1139. We find that the discrepancy between the X-ray luminosity of 2M1139 and TWA 5B is consistent with the spread in X-ray luminosity in the Orion Nebula Cluster for BDs of similar spectral types. Though rotation may play a role in the X-ray activity of ultracool dwarfs like 2M1139 and TWA 5B, the discrepancy cannot be explained by rotation alone. We also examine two X-ray bright objects in the field of view of our Chandra observations and find one to be of spectral type K0IV and identify it as a possible RS Canum Venaticorum, and another X-ray bright object whose light curve clearly shows the decay phase of an X-ray flare.
- OSTI ID:
- 21578310
- Journal Information:
- Astrophysical Journal, Vol. 736, Issue 1; Other Information: DOI: 10.1088/0004-637X/736/1/67; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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