Double white dwarf merger products among high-mass white dwarfs

Understand

Double white dwarf (double-WD) binaries may merge within a Hubble time and produce high-mass WDs.

• Compared to other high-mass WDs, the double-WD merger products have higher velocity dispersion because they are older.
• With the power of Gaia data, we show strong evidence for double-WD merger products among high-mass WDs by analyzing the transverse-velocity distribution of more than a thousand high-mass WDs (0.8--1.3 $M_\odot$).
• We estimate that the fraction of double-WD merger products in our sample is about 20 %.