A flare of the H2O maser W31(1)

ATel #17860; Ashimbaeva, Nuriya, Lekht, Evgeny (Moscow State University, Sternberg Astronomical Institute), Shoutenkov, Vladimir (Pushchino Radio Astronomy Observatory, Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences)
on 30 Jun 2026; 23:43 UT
Credential Certification: Nuriya Ashimbaeva (nta2@yandex.ru)

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We report a flare from the source of maser radio emission at 22.235 GHz in W31(1) (also known as G010.5+0.023 and G01.47+0.27). From the catalogue of F. Han et al. (1995, Purple Mountain Observatory, 14, 185), the coordinates of the source are RA J2000 = 18 08 38.418, DEC J200 = -19 51 51.69. The source is associated with an ultracompact H II region at a distance of about 5.8 kpc (P. Hofner & E. Churchwell, 1986, ApJ, 375, L25). Observations were carried out using the 22-metre radio telescope at Pushchino, Russia, and monitoring of this object began in mid-2016. The flare spectrum contains a strong peak at VLSR = 68.6 km/s. The history of its flux density variations in 2026 was: Feb 18 - 100 Jy; Mar 18 - 63 Jy; Apr 15 - 244 Jy; May 27 - 287 Jy; Jun 23 - 5117 Jy; Jun 24 - 5678 Jy; Jun 25 - 3550 Jy (there were bad weather conditions on the last day, it rained and there is a possibility that this affected the decrease in flux). In this case, the intensity in the line at VLSR = 58.8 km/s remained practically unchanged and was about 250 Jy.