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Chandra Identification of the Transient in Terzan 5: Not the 2000 Transient.

ATEL # 2974; D. Pooley (Eureka Scientific), J. Homan (MIT), C. Heinke (Alberta), M. Linares (MIT), D. Altamirano (Amsterdam), W. Lewin (MIT)
on 26 Oct 2010; 23:10 UT
Password Certification: dave pooley (

Subjects: X-ray, Binaries, Globular Clusters, Neutron Stars, Transients
Referred to by ATEL #: 3000, 3044

We triggered a Chandra ToO observation of the ongoing outburst of a transient source in the globular cluster Terzan 5 (ATel #2919, #2920, #2922, #2924, #2929, #2932, #2933, #2937, #2939, #2940, #2946, #2952, #2958). The 9.9 ks observation was taken with the ACIS S3 chip in imaging mode and began on 2010-10-24 at 19:30:29 UTC.

Inspection of the new Chandra data (ObsID 11051) reveals three low-luminosity X-ray sources that are also seen in a deeper Chandra observation (ObsID 3798) from 2003 (Heinke et al. 2006; their CX2, CX4, and CX5). The positions are in excellent agreement and allow us to identify the transient currently in outburst as CXOGlb J174804.8-244648 (their CX25) at 17:48:04.831(4), -24:46:48.87(6) (J2000) from their Table 1. This source was identified as a quiescent LMXB candidate by Heinke et al. (2006), and we quote the position from the deeper observation as it is better determined.

This new transient is not the same as the transient in 2000, which is identified in Heinke et al. (2006) as CX3 at 17:48:05.236, -24:46:47.38 in their Table 1. CX3 was assumed at the time to be EXO 1745-245.

A comparison image is available at

We thank the entire Chandra staff for their help in executing this observation.

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