Possible nature of the new transient MAXI J1752-457
ATel #16902; H. Negoro, M. Nakajima (Nihon U.), T. Mihara (RIKEN), M. Serino (AGU), W. Iwakiri (Chiba U.), Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, K. Tatano, H. Nishio (Nihon U.), T. Kawamuro, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.), and M. Sugizaki (Kanazawa U.)
on 12 Nov 2024; 09:29 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)
The newly discovered MAXI J1752-457 is a short X-ray transient detected on November 9 (Serino et al. ATel #16898). Due to the Sun angle constraint, the Swift/XRT and NICER are not observable, and the nature of the source is still quite unknown.
From MAXI/GSC data during this burst-like event, we found that the X-ray flux declined exponentially with a time constant of 0.10 +/- 0.03 d and 0.08 +/- 0.01 d in the 2-4 keV and 4-10 keV band, respectively, indicating spectral softening during the decay. All errors quoted in this analysis are at the 90% confidence interval. The spectra can be well described with an absorbed blackbody model with a column density fixed at 1e21 cm^2 (obtained from w3nh in heasarc.gsfc.nasa.gov). The blackbody temperature decreased as 1.77 (+0.16, -0.14) keV at 18:23 UT on Nov. 9, 1.63 (+0.25, -0.21) keV at 19:56, and 1.20 (+0.19, -0.16) keV from 21:29 - 03:41 (an average of five scan transits). This results suggest this transient event to be a long X-ray burst from an uncatalogued neutron star X-ray binary.
In this case, we also obtained a spherical radius of about 10 km and bolometric luminosity of 1.3e38 erg/s at the peak flux assuming the source distance of 8 kpc.
On the other hand, the short time profile is also reminiscent of a very fast X-ray transient (VFXTs) like MAXI J1957+032 (e.g., Negoro et al. ATel #7504; Beri et al. 2019, MNRAS 486, 1620; Sanna et al. 2022, MNRAS 516, L76). However, the spectra of MAXI J1957+032 could be represented by a power-law, which requires heavy intrinsic absorption (nH ~ 1e23) for MAXI J1752-457 spectra. Longer decay time-constants of 1-2 d and 0.6-0.7 d in MAXI J1957+032 (Beri et al. 2019) are also different from this case.
Finally, we note that a probable tidal disruption event EP240809a (Liu et al. ATel #16765; Zhu et al. ATel #16767) is positionally consistent with MAXI J1752-457 (only 5 arcmin apart from the best position). The peak flux of EP240809a was, however, lower than that of MAXI J1752-457 by about three orders of magnitude, and a power-law spectrum is also expected.
NuSTAR observations are planed (PI. S. Pike). Followup observations in multi-wavelengths are encouraged.
We thank Dr. Dongyue Li for pointing out the possible coincidence of EP240809a.
MAXI data of MAXI J1752-457
