SRGA J181414.6-225604: A New Galactic Symbiotic X-Ray Binary Outburst Triggered by an Intense Mass-loss Episode of a Heavily Obscured Mira Variable

We present the discovery and multiwavelength characterization of SRGA J181414.6-225604, a Galactic hard X-ray transient discovered during the ongoing SRG/ART-XC sky survey. Using data from the Palomar Gattini-IR survey, we identify a spatially and temporally coincident variable infrared (IR) source, IRAS 18111-2257, and classify it as a very-late-type (M7-M8), long-period (1502 +/- 24 days), and luminous (M ( K ) approximate to -9.9 +/- 0.2) O-rich Mira donor star located at a distance of approximate to 14.6(+2.9) (-2.3) kpc. Combining multicolor photometric data over the last approximate to 25 yr, we show that the IR counterpart underwent a recent (starting approximate to 800 days before the X-ray flare) enhanced mass-loss (reaching approximate to 2.1 x 10(-5) M (circle dot) yr(-1)) episode, resulting in an expanding dust shell obscuring the underlying star. Multi-epoch follow-up observations from Swift, NICER, and NuSTAR reveal a approximate to 200 day long X-ray outburst reaching a peak luminosity of L (X) approximate to 2.5 x 10(36) erg s(-1), characterized by a heavily absorbed (N (H) approximate to 6 x 10(22) cm(-2)) X-ray spectrum consistent with an optically thick Comptonized plasma. The X-ray spectral and timing behavior suggest the presence of clumpy wind accretion, together with a dense ionized nebula overabundant in silicate material surrounding the compact object. Together, we show that SRGA J181414.6-225604 is a new symbiotic X-ray binary in outburst, triggered by an intense dust-formation episode of a highly evolved donor. Our results offer the first direct confirmation for the speculated connection between enhanced late-stage donor mass loss and the active lifetimes of symbiotic X-ray binaries.