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ATEL #16108							    ATEL #16108

Title:	LEIA detected a new X-ray outburst from MAXI J1810-222, and
		several outbursts from nearby sources in the Galactic center region
Author:	H. N Yang, M. J Liu, Y. Liu, Z. X. Ling, C. Zhang, H. Q. Cheng,
		C. Z. Cui, D. W. Fan, H. B. Hu, J. W.Hu, M. H. Huang, C. C. Jin, D.
		Y. Li, H. Y. Liu, M. Sugizaki, H. Sun, H. W. Pan, W. X. Wang, Y. L.
		Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, 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:	30 Jun 2023; 15:42 UT
Subjects:X-ray, Binary, Black Hole

We report on a new X-ray outburst from the X-ray transient MAXI J1810-222
detected by LEIA (Lobster Eye Imager for Astronomy). The position of the
LEIA source is R.A. = 273.168 deg, DEC = -22.317 deg with an uncertainty
of 1.5 arcmin (radius, 90%C.L. statistical and systematic), which is 25.5
arcseconds away from the improved position of MAXI J1810-222 obtained by
Swift UVOT. The source was observed several times by LEIA on 2023-06-22
and 2023-06-25. The spectrum of the last observation at 2023-06-25T10:00:19
can be fitted with an absorbed powerlaw with N_H fixed at 6.0e21 cm^-2
(according to the Swift observation on 2023-06-11) and a photon index of
1.59+/-0.34, giving an unabsorbed 0.5 - 4.0 keV flux of 9.0(+/-1.5)e-10
erg/s/cm^2. Before that, the source was detected by LEIA once at 2023-05-19T09:58:38
with a lower unabsorbed flux of 1.1(+/-0.6)e-10 erg/s/cm^2. However, the
source was not detected on 2023-05-29, 2023-06-05 and 2023-06-07 at a flux
limit of a few times e-11 erg/s/cm^2. Thus, we suggest that the source
is likely to enter a new outburst period.

Aside from MAXI J1810-222, several outbursts from known X-ray sources near
the Galactic center region were also detected by LEIA in June, including
GRS 1739-278, GRS 1747-312, 1RXS J173546.9-302859, and 4U 1722-30. The
outburst of GRS 1739-278 detected with LEIA was reported by Li et al. (ATel
#16102). The highest unabsorbed fluxes of others detected with LEIA are
2.1(+/-1.3)e-10 erg/s/cm^2 for GRS 1747-312 (with N_H=0.86+/-0.64 e22 cm^-2
and a photon index of 1.93+/-1.43), 1.5(+/-0.8)e-9 erg/s/cm^2 for 1RXS
J173546.9-302859 (with N_H=1.37+/-0.51 e22 cm^-2 and a photon index of
1.77+/-0.83), and 5.0(+/-2.4)e-9 erg/s/cm^2 for 4U 1722-30 (with N_H=1.82+/-0.30
e22 cm^-2 and a photon index of 2.52+/-0.46).

LEIA(Zhang et al. 2022, ApJL, 941, 2) is a soft X-ray Lobster-eye imager
(0.5 - 4.0keV) 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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