Aql X-1 --- on the way to absolute record
ATel #16169; V. V. Vlasyuk, O. I. Spiridonova, A. S. Moskvitin, O. A. Maslennikova (Special Astrophysical Observatory of the Rus. Ac. Sci.)
on 2 Aug 2023; 23:07 UT
Credential Certification: Alexander Moskvitin (mosk@sao.ru)
Subjects: Optical, Transient
As it was reported by K.Alabarta et al. (ATel #16147), the Soft X-ray Transient Aql X-1 undergo a new outburst since July 23. Its brightness increased to râ=17.52 on July 24, 2023 (MJD 60149.39).
We performed the brightness periodical inspection for Aql X-1 with the 1-m and 0.5-m SAO RAS optical telescopes. According to our preliminary estimates its brightness in quiescence was about R = 18.25 +/- 0.03 on July 04 (MJD = 60129.9). First sign on the next outburst was detected with the 1-m telescope at level R = 17.53 +/- 0.03 on July 22 (MJD = 60147.9). Our following measurements with the same instrumentation indicate on fast growing of Aql X-1 brightness and are present in table. The last night measurements were done twice with 3 hour interval and showed that outburst is in progress yet.
| Date | MJD | R_mag | Err R |
| 20230725 | 60150.88 | 17.09 | 0.02 |
| 20230731 | 60156.93 | 16.35 | 0.03 |
| 20230801 | 60157.90 | 16.20 | 0.04 |
| 20230802 | 60158.76 | 15.84 | 0.03 |
| 20230802 | 60158.91 | 15.77 | 0.04 |
These values as well as following growth (0.07 mag per 3 hours) shows that source Aql X-1 is very close to its absolute brightness record for the last decade (see ATel #6447).
The errors of brightness estimates are about 0.04 mag and caused by bright Moon sky level mainly.
Further observations of Aql X-1 in X-ray, UV, Optical, IR and Radio ranges are highly encouraged.
