# ALMA monitoring of mm line variation in IRC+10216: I. Overview of millimeter variability

## TL;DR

This study presents the first ALMA monitoring of millimeter line variability in the carbon star IRC+10216 over 817 days, revealing diverse line variations that may probe stellar wind processes.

## Contribution

It provides the first long-term ALMA observations of millimeter line variability in IRC+10216, expanding understanding of circumstellar dynamics.

## Key findings

- Detected 148 known molecular transitions and 81 unidentified lines.
- Most lines vary in phase or anti-phase with near-infrared light.
- Some line variations match single dish results, others do not.

## Abstract

Temporal variation of millimeter lines is a new direction of research for evolved stars. It has the potential to probe the dynamical wind launching processes from time dimension. We report here the first ALMA (Atacama Large Millimeter Array) results that cover 817 days of an on-going monitoring of 1.1 mm lines in the archetypal carbon star IRC +10216. The monitoring is done with the compact 7-m array (ACA) and in infrared with a 1.25 m telescope in Crimea. A high sensitivity of the cumulative spectra covering a total of ~7.2 GHz between 250 - 270 GHz range has allowed us to detect about 148 known transitions of 20 molecules, together with more of their isotopologues, and 81 unidentified lines. An overview of the variabilities of all detected line features are presented in spectral plots. Although a handful of lines are found to be very possibly stable in time, most other lines are varying either roughly in phase or in anti-correlation with the near-infrared light. Several lines have their variations in the ALMA data coincident with existing single dish monitoring results, while several others do not, which requires an yet unknown mechanism in the circumstellar envelop to explain.