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ATEL #16061							    ATEL #16061

Title:	LEIA detected possible brightening of SAX J1747.0-2853 and
		X-ray variability of 1A 1742-294 in the Galactic Center region
Author:	D. Y. Li, H. Q. Cheng, Z. X. Ling, Y. Liu, C. Zhang, C. Z.
		Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, C. C. Jin, J. Q.
		Li, H. Y. Liu, M. J Liu, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang,
		Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N Yang, M. Zhang, W. D. Zhang, D.
		H. Zhao and W. Yuan (NAOC, CAS), on behalf of the LEIA and Einstein
		Probe team
Queries:	ep_ta@nao.cas.cn
Posted:	29 May 2023; 15:56 UT
Subjects:X-ray, Black Hole, Neutron Star, Transient

LEIA detected possible brightening of SAX J1747.0-2853 and X-ray variability
of 1A 1742-294 in the Galactic Center region, where MAXI reported the detection
of a new X-ray outburst since May 24 2023(ATel #16059). The Galactic Center
region has been regularly monitored by LEIA in the last few months. In
the latest observations taken on May 26 2023, within the field of view
(1.5 degrees, FWHM) of MAXI/GSC detection ((l, b) = (359.944, -0.046)),
LEIA detected two sources at (RA=266.782, Dec=-28.85, uncertainty=2.6 arcmin)
and (RA=266.535, Dec=-29.499, uncertainty=2.2 arcmin), that are spatially
consistent with SAX J1747.0-2853 and 1A 1742-294, respectively.

SAX J1747.0-2853 remained undetected in all previous observations of LEIA
with a typical cadence of ~10 days and a typical exposure time of ~700s,
indicating an upper limit of ~4e-11 erg/s/cm2; whereas an X-ray source
was detected around this position in the last two observations at 2023-05-26T05:28:30
and 2023-05-26T07:02:48. Assuming the source is indeed SAX J1747.0-2853
and a spectral shape of absorbed powerlaw with a photon index of 2.0 and
NH of 7e+22 cm^-2 (Wijnands et al. 2002, ApJ, 579, 422), its unabsorbed
0.5-4 keV flux was (3.5+/-1.2)e-9 erg/s/cm2 and (9.3+/-7.0)e-10 erg/s/cm2,
respectively, implying that SAX J1747.0-2853 has entered a new outburst.

The other source was firstly detected by LEIA on May 12 2023. Assuming
it is 1A 1742-294 and a spectral shape of absorbed powerlaw with a photon
index of 2.0 and NH of 6e+22 cm^-2 (Lutovinov et al. 2000, arXiv:astro-ph/0009349),
its unabsorbed 0.5-4 keV flux was (1.8+/-1.0)e-9 erg/s/cm2. During the
following observations till May 26 2023, 1A 1742-294 shows moderate variability
with its 0.5-4 keV unabsorbed flux varies in the range of ~6e-10 to 3e-9
erg/s/cm2.

LEIA (Zhang et al, ApJL, 941, 2) is a soft X-ray lobster-eye imager (0.5
- 4.0 keV) with a FoV of 340 square degrees aboard the experimental satellite
SATech-01 of the CAS, launched on July 27, 2022. The above result is preliminary
and the final result will be published elsewhere.

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