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GRB 190714A is an X-ray flare from 2E 1624.6+1504/UCAC4 525-061488

ATel #12944; H. Negoro (Nihon U.), W. Iwakiri, T. Sato (Chuo U.), J. Kennea (PSU), K. Page (U. Leicester), M. Serino (AGU), T. Mihara (RIKEN), Y. Tsuboi (Chuo U.), M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), S. Nakahira, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Nishida, A. Yoshida (AGU), R. Sasaki, H. Kawai (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, M. Sugizaki, M. Oeda, K. Shiraishi (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU) report on behalf of the MAXI team:
on 16 Jul 2019; 15:22 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Star, Variables

Swift-XRT performed 7 tiled followup observations for GRB 190714A (Serino et al. GCN #25068) from 15:32:40 UT on July 14th, 2019 (T0 +7.9 ks) to 15:56:45 (T0 +9.3 ks), and detected one bright source inside the MAXI error region.

The XRT automatic analysis shows the following source position (Evans GCN 25069; also see Evans et al. 2014, ApJS, 210, 8).

RA (J2000): 246.72610 deg = 16h 26m 54.26s
Dec (J2000): 14.96329 deg = +14d 57' 47.8"
(radius error at a 90% confidence level: 2.2")

The source position is consistent with that of the X-ray source 2E 1624.6+1504, which is the high proper-motion M star UCAC4 525-061488 (3.1" away from for the J2000 position, and 1.1" away if the proper motion is taken into account (Gaia DR2, CDS/ADC Collection of Electronic Catalogues, 1345, 0 (2018)).

The XRT light curve showed variations (no fading) in X-ray flux during the 371 sec observation, and the peak and mean X-ray count rates were 2.0 +/- 0.4 c/s and 1.53 +/- 0.15 c/s, respectively.

The X-ray spectrum is well described with an absorbed power-law model with intrinsic N_H of 1.9 (+1.3, -1.1) x 10^21 cm^-2 and a photon index of 2.4 +/- 0.4. The 0.3-10 keV X-ray flux is 3.1 (+0.7, -0.5) x 10^-11 erg/cm^2/s (absorbed) and 5.3 (+2.1, -1.0) x 10^-11 erg/cm^2/s (unabsorbed).

If the source is UCAC4 525-061488, 34.7 pc away, X-ray luminosities in the first MAXI and the followup Swift observations are about 7.9 x 10^32 erg/s (absorbed 2-10 keV) and 7.6 x 10^30 erg/s (unabsorbed 0.3-10 keV), respectively. These are consistent with those of an X-ray flare and a steady component of a dMe star. We also note that the LAMOST optical spectrum (Luo et al. 2016yCat.5149....0L) suggests that UCAC4 525-061488 is a dMe star because the Balmer lines are seen in their spectrum. Thus, we conclude that GRB 190714A is very likely to be an X-ray flare from the M (dMe) star 2E 1624.6+1504/UCAC4 525-061488.