Multiwavelength Observations of the Hot DB Star PG 0112+104

TL;DR

This study provides a detailed multiwavelength analysis of the hot DB white dwarf PG 0112+104, determining its temperature, gravity, and chemical composition, and discusses its implications for stellar pulsation boundaries.

Contribution

It offers new spectroscopic and photometric data, refining the star's physical parameters and chemical abundances, and reevaluates its role in the V777 Her instability strip boundary.

Findings

Effective temperature of 31,300 K with ±500 K uncertainty.

Carbon abundance determined as log N(C)/N(He) = -6.15 ± 0.23.

No detection of other heavy elements in the photosphere.

Abstract

We present a comprehensive multiwavelength analysis of the hot DB white dwarf PG 0112+104. Our analysis relies on newly-acquired FUSE observations, on medium-resolution FOS and GHRS data, on archival high-resolution GHRS observations, on optical spectrophotometry both in the blue and around Halpha, as well as on time-resolved photometry. From the optical data, we derive a self-consistent effective temperature of 31,300+-500 K, a surface gravity of log g = 7.8 +- 0.1 (M=0.52 Msun), and a hydrogen abundance of log N(H)/N(He) < -4.0. The FUSE spectra reveal the presence of CII and CIII lines that complement the previous detection of CII transitions with the GHRS. The improved carbon abundance in this hot object is log N(C)/N(He) = -6.15 +- 0.23. No photospheric features associated with other heavy elements are detected. We reconsider the role of PG 0112+104 in the definition of the blue edge of the V777 Her instability strip in light of our high-speed photometry, and contrast our results with those of previous observations carried out at the McDonald Observatory.