XRISM/Xtend Transient Search (XTS) detected a flux increase of XRISM J1236-6432

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https://www.astronomerstelegram.org/?read=17232

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http://hdl.handle.net/11603/40333

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UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
UMBC Faculty Collection
UMBC Physics Department

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Author/Creator ORCID

https://orcid.org/0000-0002-4656-6881

Date

2025-06-16

Type of Work

articles
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Citation of Original Publication

Pottschmidt, K., T. Kiyomoto, K. Fukushima, Y. Kanemaru, S. Ogawa, et al. “XRISM/Xtend Transient Search (XTS) Detected a Flux Increase of XRISM J1236-6432.” The Astronomer’s Telegram, June 16, 2025. https://www.astronomerstelegram.org/?read=17232.

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Abstract

XRISM/Xtend Transient Search (XTS) detected a gradual increase in the flux of the X-ray source XRISM J1236-6432 from 2025-6-12 to 2025-6-13 TT. The source position is determined to be (R.A., Dec.) = (188.884, -64.528), with a systematic error of ∼ 40 arcsec. A plausible counterpart is the 4XMM J123530.3-643125, which is located ∼ 20 arcsec apart from the position of XRISM J1236-6432. All statistical uncertainties in this report are provided as a 90% confidence level unless stated otherwise. In the duration of ∼ 80 ks, the flux increased several times. The average flux is calculated as 5 × 10⁻¹³ erg s⁻¹ cm⁻² (0.4 – 10.0 keV), using an absorbed power-law model. This result is one order of magnitude greater than the catalog flux of the 4XMM J123530.3-643125. The photon index and column density are derived as 1 and < 3 × 10²⁰ cm⁻², respectively. We derived the above systematic error for the flux by comparing our derived values for the sources detected with XTS in several observations with those for the corresponding X-ray counterparts. We estimated the systematic error for the source position from the separations between the detected sources with the corresponding counterparts in the same field of view.