Speaker
Description
The population of known white dwarfs (WDs) has expanded rapidly with Gaia observations, the number of WDs and their candidates have exceeded beyond one million. High-resolution surveys like the ESO SN Ia Progenitor Survey (SPY) provided gold-standard parameters for ~1,000 WDs using UVES/VLT spectra. However, precious observations with such precision and high resolution are not meant for the ordinary high population of existing WDs and their candidates. The spectral data of vast majority of WDs are only accessible through smaller-calibre telescopes, lower resolution spectrographs, and with a generally lower signal-to-noise ratio spectra from surveys such as SDSS and LAMOST.
Traditional template-fitting methods often struggle with these noisy spectra, as the uncertainty in the fundimental parameters of a WD, such as effective temperature (T_eff) and surface gravity gravity (log_G), would grow rapidly with decreasing spectral quality, and is thus more suitable for higher-resolution spectra than the vast majority of WD spectra from survey telescopes. In this study, we present an alternative method in characterizing WDs, especially the ones with lower-resolution spectra available only. We focus on the basic spectral features of DA (the most common, hydrogen-rich) WDs, by utilizing the equivalent widths (EWs) of the Balmer absorption lines and their respective ratios as primary indicators, we derived a relation between the basic WD parameters and the behavior of their Balmer absorption lines. And we further established a specialized method to determine their atmospheric parameters through these features.