Dramatic infrared variability of WISE J1810-3305: catching early dust ejection during the thermal pulse of an AGB star?

TL;DR

This paper reports the discovery of WISE J1810-3305, an AGB star undergoing a rare, massive dust ejection event during a thermal pulse, observed through its dramatic infrared variability and spectral characteristics.

Contribution

It presents the identification of a rare post-AGB star with early dust ejection evidence, providing a unique observational window into stellar evolution during thermal pulses.

Findings

Detected significant infrared brightening in WISE J1810-3305.

Observed multiwavelength variability similar to Sakurai's Object.

Identified as a rare case of early dust ejection during an AGB star's thermal pulse.

Abstract

We present the discovery of a source with broadband infrared photometric characteristics similar to Sakurai's Object. WISE J180956.27-330500.2 (hereafter, J1810-3305) shows very red WISE colors, but a very blue 2MASS [K] vs. WISE [W1 (3.4 micron)] color. It was not visible during the IRAS era, but now has a 12 micron flux well above the IRAS point source catalog detection limit. There are also indications of variability in historical optical photographic plates, as well as in multi-epoch AKARI mid-infrared measurements. The broadband infrared spectral energy distribution, post-IRAS brightening and multiwavelength variability are all characteristics also shared by Sakurai's Object - a post asymptotic giant branch (post-AGB) star which underwent a late thermal pulse and recently ejected massive envelopes of dust that are currently expanding and cooling. Optical progenitor colors suggest that J1810-3305 may have been of late spectral class. Its dramatic infrared brightening, and the detection of a late-type optical counterpart are consistent with a scenario in which we have caught an extremely massive dust ejection event (in 1998 or shortly before) during the thermal pulse of an AGB star, thus providing a unique opportunity to observe stellar evolution in this phase. J1810-3305 is the only source in the entire WISE preliminary data release with similar infrared SED and variability, emphasizing the rarity of such sources. Confirmation of its nature is of great importance.