IRAS 17449+2320 AS A POST-MERGER

• it has the strong magnetic field
• The magnetic field modulus is around 6 kG (Korčáková at al. 2022). That it is on the order of the strongest magnetic Ap stars.
• The strong magnetic field may be generated by the mixing during the merger (Schneider et al., 2019) .
• it is a slow rotator
• $v\; sin\; i$ = 9.1 km/s (Korčáková at al. 2022). However, even this value is overestimated. It was obtained by fitting standard spectra that misinterpret the Zeeman splitting as a rotational broadening.
• Even if the newly born star rotates critically, the magnetic field slows down it rapidly (Schneider et al., 2019) .
• large space velocity
• The space velocity toward the north galactic pole is 8.470 km/s (Korčáková at al. 2022).
• Such anomalous space velocity indicates that the star may be kicked from the birth cluster due to the interaction with another star in the cluster. When this happen to the binary, it usually has a large eccentricity and small semi-major axis. In such situation, the tidal forces circularise the orbit. As a consequence of the momentum conservation law, the semi-major axis shrink. And binary may, or may not merge.
• UV excess
• The star has UV excess (Korčáková at al. 2022).
• Most of FS CMa stars, including IRAS 17449+2320, are located around the terminal main sequence. At this stage, a post-merger is out of the thermal equilibrium, i.e., it is overluminous. (Schneider et al., 2019).