V838 Monocerotis Shows First Evidence of Pulsations in Stellar Merger Remnant
Astronomers observed the deepest dimming event since 2006 in V838 Monocerotis, a star formed from a merger in 2002, and detected pulsation shocks similar to those in red supergiants and Mira variables. The dimming was caused by freshly formed circumstellar dust blocking starlight, while spectroscopic analysis revealed hydrogen recombination lines and blueshifted metal lines characteristic of pulsation shocks. This discovery provides the first observational confirmation that stellar merger remnants can develop pulsational instability, validating theoretical predictions about post-merger stellar evolution.
V838 Monocerotis, the remnant of a stellar merger that occurred in 2002, experienced a dramatic dimming event in late 2025—the deepest observed since 2006. Using multiband photometry and high-resolution spectroscopy, researchers characterized the dimming as caused by a transiting clump of freshly formed circumstellar dust composed of small silicate or alumina grains, with dust extinction parameters consistent with the observed photometric color evolution. During the recovery phase, the star exhibited hydrogen recombination lines in emission with anomalous ratios matching those of pulsating Mira stars near maximum light, along with blueshifted low-ionization metal lines tracing shock-affected gas. These spectroscopic features are interpreted as arising from a sub-photospheric pulsation shock, with evidence suggesting the dimming itself was triggered by a preceding pulsation shock earlier in 2025. This represents the first observational evidence for pulsations in a stellar merger remnant, confirming theoretical predictions that post-merger objects can develop pulsational instability similar to red supergiants and Mira variables.
What different sources said
- arXiv astro-phCenter
Dimming and pulsation shock of the coalesced star V838 Monocerotis
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