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Further Optical Observations of Aql X-1

ATEL # 2748; Tolga Guver (Univ. of Arizona), Andrea Kunder (CTIO), and Feryal Ozel (Univ. of Arizona)
on 20 Jul 2010; 21:19 UT
Password Certification: Tolga Guver (

Subjects: Optical, Binaries, Neutron Stars, Transients
Referred to by ATEL #: 2850, 2871

Kayhan et al. (ATEL #2742) and Maitra et al. (ATEL #2744) recently reported a new outburst of the low mass X-ray binary Aql X-1. Following these reports, we observed the source in the B and R bands using the 90" Bart J. Bok Telescope of the Steward Observatory at Kitt Peak on July 19 UTC. Using the 90Prime detector, we obtained R and B band images with exposure times of 250 and 500 seconds at JD 2455396.8494 and 2455396.8227, respectively. We converted instrumental magnitudes to the standard system using 9 nearby stars and the USNO B1.0 catalog (Monet et al. 2003). We found that the R and B band magnitudes of the source are 17.187 +/- 0.015 and 18.722 +/- 0.011. As in Maitra et al., our magnitudes include the unrelated interloper 0.5" away (Chevalier et al. 1999; Maitra & Bailyn 2008). These measurements show that the optical brightness of the source continues to increase. Due to overcast weather conditions no future observations are planned.

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