The effect of photospheric heavy elements on the hot DA white dwarf temperature scale

M. A. Barstow, Ivan - Hubeny, J. B. Holberg

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Using the latest non-local thermodynamic equilibrium (non-LTE) synthetic spectra and stellar model calculations, we have evaluated the potential effect of the presence of heavy elements in the photospheres of hot H-rich DA white dwarfs. In particular, we have examined their influence on the effective temperature and surface gravity perceived from analysis of the Balmer line profiles. It is apparent that both the inclusion of non-LTE effects in the models and significant quantities of heavy elements act independently to lower the value of Teff determined from a particular spectrum. Hence, the true effective temperatures of the heavy element-rich DA white dwarfs, currently estimated to be above 55 000 K, are apparently lower than previously reported from pure-H LTE analyses, by some 4000-7000 K. We do not see any similar influence on measurements of log g. This work concentrates on a group of relatively bright well-studied objects, for which heavy element abundances are known. As a consequence of this, establishment of correct temperatures for all other hot white dwarfs will require a programme of far-UV spectroscopy in order to obtain the essential compositional information. Since only stars with effective temperatures lying notionally in the range from ≈55 000 to 70 000 K (52 000-62 000 K when the non-LTE effects and heavy elements are taken into account) have been considered here, important questions remain regarding the magnitude of any similar effects in even hotter white dwarfs and pre-white dwarfs. The resulting implications for the plausibility of the evolutionary link between the main hot DA population and their proposed precursors, the H-rich central stars of planetary nebulae, need to be investigated.

Original languageEnglish (US)
Pages (from-to)520-534
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume299
Issue number2
StatePublished - Sep 11 1998
Externally publishedYes

Fingerprint

temperature scales
heavy elements
thermodynamic equilibrium
thermodynamics
temperature
stars
stellar models
local thermodynamic equilibrium
planetary nebulae
photosphere
spectroscopy
gravity
effect
inclusions
gravitation
profiles

Keywords

  • Stars: abundances
  • Stars: atmospheres
  • Ultraviolet: stars
  • White dwarfs
  • X-rays: stars

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

The effect of photospheric heavy elements on the hot DA white dwarf temperature scale. / Barstow, M. A.; Hubeny, Ivan -; Holberg, J. B.

In: Monthly Notices of the Royal Astronomical Society, Vol. 299, No. 2, 11.09.1998, p. 520-534.

Research output: Contribution to journalArticle

@article{b6d6d59358e2485c914da95685fe30c5,
title = "The effect of photospheric heavy elements on the hot DA white dwarf temperature scale",
abstract = "Using the latest non-local thermodynamic equilibrium (non-LTE) synthetic spectra and stellar model calculations, we have evaluated the potential effect of the presence of heavy elements in the photospheres of hot H-rich DA white dwarfs. In particular, we have examined their influence on the effective temperature and surface gravity perceived from analysis of the Balmer line profiles. It is apparent that both the inclusion of non-LTE effects in the models and significant quantities of heavy elements act independently to lower the value of Teff determined from a particular spectrum. Hence, the true effective temperatures of the heavy element-rich DA white dwarfs, currently estimated to be above 55 000 K, are apparently lower than previously reported from pure-H LTE analyses, by some 4000-7000 K. We do not see any similar influence on measurements of log g. This work concentrates on a group of relatively bright well-studied objects, for which heavy element abundances are known. As a consequence of this, establishment of correct temperatures for all other hot white dwarfs will require a programme of far-UV spectroscopy in order to obtain the essential compositional information. Since only stars with effective temperatures lying notionally in the range from ≈55 000 to 70 000 K (52 000-62 000 K when the non-LTE effects and heavy elements are taken into account) have been considered here, important questions remain regarding the magnitude of any similar effects in even hotter white dwarfs and pre-white dwarfs. The resulting implications for the plausibility of the evolutionary link between the main hot DA population and their proposed precursors, the H-rich central stars of planetary nebulae, need to be investigated.",
keywords = "Stars: abundances, Stars: atmospheres, Ultraviolet: stars, White dwarfs, X-rays: stars",
author = "Barstow, {M. A.} and Hubeny, {Ivan -} and Holberg, {J. B.}",
year = "1998",
month = "9",
day = "11",
language = "English (US)",
volume = "299",
pages = "520--534",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "2",

}

TY - JOUR

T1 - The effect of photospheric heavy elements on the hot DA white dwarf temperature scale

AU - Barstow, M. A.

AU - Hubeny, Ivan -

AU - Holberg, J. B.

PY - 1998/9/11

Y1 - 1998/9/11

N2 - Using the latest non-local thermodynamic equilibrium (non-LTE) synthetic spectra and stellar model calculations, we have evaluated the potential effect of the presence of heavy elements in the photospheres of hot H-rich DA white dwarfs. In particular, we have examined their influence on the effective temperature and surface gravity perceived from analysis of the Balmer line profiles. It is apparent that both the inclusion of non-LTE effects in the models and significant quantities of heavy elements act independently to lower the value of Teff determined from a particular spectrum. Hence, the true effective temperatures of the heavy element-rich DA white dwarfs, currently estimated to be above 55 000 K, are apparently lower than previously reported from pure-H LTE analyses, by some 4000-7000 K. We do not see any similar influence on measurements of log g. This work concentrates on a group of relatively bright well-studied objects, for which heavy element abundances are known. As a consequence of this, establishment of correct temperatures for all other hot white dwarfs will require a programme of far-UV spectroscopy in order to obtain the essential compositional information. Since only stars with effective temperatures lying notionally in the range from ≈55 000 to 70 000 K (52 000-62 000 K when the non-LTE effects and heavy elements are taken into account) have been considered here, important questions remain regarding the magnitude of any similar effects in even hotter white dwarfs and pre-white dwarfs. The resulting implications for the plausibility of the evolutionary link between the main hot DA population and their proposed precursors, the H-rich central stars of planetary nebulae, need to be investigated.

AB - Using the latest non-local thermodynamic equilibrium (non-LTE) synthetic spectra and stellar model calculations, we have evaluated the potential effect of the presence of heavy elements in the photospheres of hot H-rich DA white dwarfs. In particular, we have examined their influence on the effective temperature and surface gravity perceived from analysis of the Balmer line profiles. It is apparent that both the inclusion of non-LTE effects in the models and significant quantities of heavy elements act independently to lower the value of Teff determined from a particular spectrum. Hence, the true effective temperatures of the heavy element-rich DA white dwarfs, currently estimated to be above 55 000 K, are apparently lower than previously reported from pure-H LTE analyses, by some 4000-7000 K. We do not see any similar influence on measurements of log g. This work concentrates on a group of relatively bright well-studied objects, for which heavy element abundances are known. As a consequence of this, establishment of correct temperatures for all other hot white dwarfs will require a programme of far-UV spectroscopy in order to obtain the essential compositional information. Since only stars with effective temperatures lying notionally in the range from ≈55 000 to 70 000 K (52 000-62 000 K when the non-LTE effects and heavy elements are taken into account) have been considered here, important questions remain regarding the magnitude of any similar effects in even hotter white dwarfs and pre-white dwarfs. The resulting implications for the plausibility of the evolutionary link between the main hot DA population and their proposed precursors, the H-rich central stars of planetary nebulae, need to be investigated.

KW - Stars: abundances

KW - Stars: atmospheres

KW - Ultraviolet: stars

KW - White dwarfs

KW - X-rays: stars

UR - http://www.scopus.com/inward/record.url?scp=0037715463&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0037715463&partnerID=8YFLogxK

M3 - Article

VL - 299

SP - 520

EP - 534

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -