Variable H-alpha Line Emission from the Central Star of the Helix Nebula

Abstract

The central star of the Helix Nebula is a hot white dwarf with unexpected hard X-ray emission. With an effective temperature of ~100,000 K, the star is a powerful source of H-ionizing radiation; the atmosphere of a stellar or planetary companion, if present, will be ionized and emit recombination lines. To probe the origin of hard X-ray emission from the Helix Nebula's central star, we have obtained multi-epoch high-dispersion spectra of the star, and found temporal variation in the H-alpha line profile over a time span of one week. The observed width and strength of the variable H-alpha emission component are consistent with the hypothesized dMe companion proposed to explain the hard X-ray emission. A dMe companion, however, cannot explain the possible detection of variable HeII and [NII] emission. Follow-up spectroscopic monitoring of the Helix Nebula central star is needed to better establish the identification of the spectral lines and their temporal behavior in order to determine the origin of the optical variability and hard X-ray emission.

Accepted for publication in the Astronomical Journal, LaTeX document, 7 pages, includes 4 figures, 2 tables

References in corpus (2)

• Chandra Reveals the X-ray Glint in the Cat's Eye
• The Enigmatic X-ray Point Sources at the Central Stars of NGC 6543 and NGC 7293

Cited by in corpus (15)

• Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1
• A Debris Disk around the Central Star of the Helix Nebula?
• The Chandra X-ray Survey of Planetary Nebulae (ChanPlaNS): Probing Binarity, Magnetic Fields, and Wind Collisions
• The Enigmatic X-ray Point Sources at the Central Stars of NGC 6543 and NGC 7293
• The Chandra Planetary Nebulae Survey (ChanPlaNS): III. X-ray Emission from the Central Stars of Planetary Nebulae
• Unraveling the Helix Nebula: Its Structure and Knots
• The creation of the Helix planetary nebula (NGC 7293) by multiple events
• Hard X-ray Emission Associated with White Dwarfs
• On the Asymmetries of Extended X-ray Emission from Planetary Nebulae
• X-Ray Emission from Central Binary Systems of Planetary Nebulae
• Hard X-ray Emission Associated with White Dwarfs II
• The Nebular Environment and Enigmatic Hard X-ray Emission of the Hot DO White Dwarf KPD 0005+5106
• Evidence for the disruption of a planetary system during the formation of the Helix Nebula
• The bow-shock and high-speed jet in the faint, 40 arcmin diameter, outer halo of the evolved Helix planetary nebula (NGC 7293)
• Introducing PyCross: PyCloudy Rendering Of Shape Software for pseudo 3D ionisation modelling of nebulae