Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface
Abstract
AM CVn binaries are a class of ultracompact, hydrogen-deficient binaries, each consisting of a white dwarf accreting helium-dominated material from a degenerate or semi-degenerate donor star. Of the 56 known systems, only Gaia14aae undergoes complete eclipses of its central white dwarf, allowing the parameters of its stellar components to be tightly constrained. Here, we present phase-resolved optical spectroscopy of Gaia14aae. We use the spectra to test the assumption that the narrow emission feature known as the 'central spike' traces the motion of the central white dwarf. We measure a central spike velocity amplitude of 13.8 ± 3.2 km s^(−1), which agrees at the 1σ level with the predicted value of 17.6 ± 1.0 km s^(−1) based on eclipse-derived system parameters. The orbital phase offset of the central spike from its expected position is 4 ± 15°, consistent with 0°. Doppler maps of the HeI lines in Gaia14aae show two accretion disc bright-spots, as seen in many AM CVn systems. The formation mechanism for the second spot remains unclear. We detect no hydrogen in the system, but we estimate a 3σ limit on H α emission with an equivalent width of −1.14 Å. Our detection of nitrogen and oxygen with no corresponding detection of carbon, in conjunction with evidence from recent studies, mildly favours a formation channel in which Gaia14aae is descended from a cataclysmic variable with a significantly evolved donor.
Additional Information
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2019 February 1. Received 2019 February 1; in original form 2019 January 16. Published: 15 February 2019. The authors would like to thank Matt Wood for helpful discussion regarding modelling of the second bright-spot, and Chris Manser for discussion regarding the Doppler maps. We would also like to thank the anonymous reviewer for the comments and suggestions. MJG acknowledges funding from an STFC studentship via grant ST/N504506/1. TRM and DTHS acknowledge STFC via grant ST/P000495/1. EC has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 677706 – WD3D). The data reduction presented in this work was carried out primarily using PAMELA and MOLLY, as well as various packages included in STARLINK. The analysis made use of PYTHON packages including NUMPY, MATPLOTLIB, SCIPY, and ASTROPY. This work is partly based on observations made with the WHT. The WHT is operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. This work is also partly based on observations made with the GTC, installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma.Attached Files
Published - stz469.pdf
Accepted Version - 1902.01213.pdf
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Additional details
- Eprint ID
- 97584
- Resolver ID
- CaltechAUTHORS:20190801-110405260
- ST/N504506/1
- Science and Technology Facilities Council (STFC)
- ST/P000495/1
- Science and Technology Facilities Council (STFC)
- 677706 – WD3D
- European Research Council (ERC)
- Created
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2019-08-01Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field