J/MNRAS/520/6111 Spectrophotometric magnetic study of MWD stars (Hardy+, 2023)
Spectrophotometric analysis of magnetic white dwarf. I.
Hydrogen-rich compositions.
Hardy F., Dufour P., Jordan S.
<Mon. Not. R. Astron. Soc. 520, 6111-6134 (2023)>
=2023MNRAS.520.6111H 2023MNRAS.520.6111H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, white dwarf ; Magnetic fields ; Photometry ; Spectroscopy ;
Optical ; Effective temperatures ; Stars, masses ;
Positional data
Keywords: stars: magnetic field - (stars:) white dwarfs -
techniques: photometric - techniques: spectroscopic
Abstract:
We present a homogeneous analysis of all DA stars labelled as magnetic
in the Montreal White Dwarf Database. Our sample is restricted to
almost all known magnetic white dwarf showing clear sign of splitting
(B ~>1-2 MG) that have parallax measurements from the second Gaia data
release, photometric data from diverse surveys and spectroscopic data
from Sloan Digital Sky Survey or archival data from the Montreal
group. We determine the atmospheric parameters (effective temperature,
surface gravity, and magnetic field strength/geometry) of all objects
using state-of-the-art model atmosphere/magnetic synthetic spectra, as
well as reclassify many objects that were prematurely labelled as
potentially magnetic. Finally, we discuss the atmospheric
parameters/field properties distribution as well as the implication on
our understanding of magnetic white dwarfs origin and evolution.
Description:
Since characterizing main-sequence magnetic properties can be rather
complicated due to their low field strengths, studying their remnants,
mostly white dwarf (WD) stars, can provide valuable information about
the magnetic characteristics of their progenitors as a whole. Studying
the incidence of magnetism among MWD stars, their distribution in
terms of mass, effective temperature, field intensity, and geometry
should provide valuable hints to help us understand their evolutionary
paths (i.e. see more in introduction section). Given the large number
of MWDs that have been identified since that study, and the mass
availability of precise trigonometric parallax measurements for
basically every object in the solar neighbourhood (i.e. Gaia surveys),
it is now more than necessary to revisit/determine the atmospheric
parameters of all known MWD in a homogeneous fashion as such an
analysis is bound to provide important clues as to the nature and
evolution of MWDs in general. As a first step, this paper will look at
all the objects that have been classified as magnetic hydrogen-rich
WDs in the Montreal White Dwarf Database (MWDD,
https://www.montrealwhitedwarfdatabase.org/).
As a first step, we aim to analyse in a homogeneous fashion known
hydrogen-rich MWDs identified in the literature. We also include
flagged as DAH by visual inspection of thousands of SDSS spectra. Most
of these MWDs have never, to our knowledge, been the subject of a
detailed analysis. Furthermore, we restrict ourselves to objects
showing clear signs of magnetic line splitting (B greater than about 2
MG). We selected all the objects with the SPtype DA and magnetic flag
in the MWDD or with spectral type DAH (510 objects). This leaves us a
final sample of 651 potentially MWDs to examine. These objects is
analysed in a homogeneous way using best available optical spectra
(i.e. see MWDD), astrometric measurements from Gaia DR2/EDR3 and
photometric measurements (either SDSS ugriz, Pan-STARRS grizy or JHK
and BVRI), see fully explanations in section 2. The tablea1.dat
provides the correspondence between the names of all objects in our
sample with Gaia source ID, MWDD ID, and the coordinates in decimal
format.
Next as explained in section 3, with synthetic magnetic spectra
models, we mainly model surface magnetic field of the stars with an
inclined and offset dipole as shown eq (1) of this section. We orient
the magnetic moment according to the inclination, and apply the dipole
offset by shifting the position vector accordingly. The parameters
used to describe the dipolar geometry are the dipole intensity Bp,
which is the magnetic field intensity at the pole of a centred dipole,
at the stellar surface, the inclination angle i between the dipole
moment m and the observer's line of sight, and the dipole offset az,
the distance between the centre of the dipole and the centre of the
star. Also, as exposed in section 3.2, when B=0 is assumed, we
estimate the effective temperature and surface gravity plus the mass
with a photometric analysis technique as presented on table2.dat for
400 objects in our 651 sample. For the 185 with magnetic fields, the
spectroscopic analysis technique is implied to retreive dipole
geometry parameters and mean B. Firstly, 140 objects well fitted with
a dipole geometry in table5.dat. Secondly, 45 objects moderately well
modelled with a dipolar geometry in table6.dat. Spectra fits images
are given for these two tables in fits folder.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 80 651 The correspondence between names of all objects
in our sample with Gaia and MWDD IDs
table2.dat 48 400 Photometric atmospheric parameters for stars
with no compelling evidence of magnetism as B=0
table5.dat 69 140 Atmospheric and dipole geometry parameters for
stars well fitted with a dipole geometry
table6.dat 69 45 Atmospheric and dipole geometry parameters for
hydrogen-rich MWD stars but are moderately well
modelled with a dipolar geometry
sp/* . 185 Individual spectra fits with various degrees
of quality using a dipolar geometry
--------------------------------------------------------------------------------
See also:
J/MNRAS/497/130 : Gaia white dwarfs within 40pc. I (Tremblay+, 2020)
J/MNRAS/486/2169 : White dwarf and subdwarf stars in SDSS DR14 (Kepler+, 2019)
J/MNRAS/455/3413 : New white dwarf and subdwarf stars in SDSS DR12
(Kepler+, 2016)
J/MNRAS/446/4078 : New white dwarf stars in SDSS DR10 (Kepler+, 2015)
J/MNRAS/429/2934 : SDSS magnetic white dwarf stars (Kepler+, 2013)
J/A+A/506/1341 : Magnetic fields in white dwarfs (Kuelebi+, 2009)
J/ApJS/219/19 : Census of nearby white dwarfs from SUPERBLINK
(Limoges+, 2015)
J/ApJS/204/5 : SDSS DR7 white dwarf catalog (Kleinman+, 2013)
J/ApJS/133/413 : BVRIJHK photometry of cool white dwarfs (Bergeron+, 2001)
J/ApJ/935/L12 : Magnetic field measurements of young white dwarfs
(Bagnulo+, 2022)
J/ApJ/885/74 : 1340 Helium rich white dwarfs in the Gaia era (Coutu+, 2019)
J/ApJ/743/138 : Spectroscopic survey of bright white dwarfs
(Gianninas+, 2011)
J/ApJ/607/426 : Catalog of white dwarfs in SDSS-DR1 (Kleinman+, 2004)
J/AJ/145/136 : Astrometry and photometry of nearby white dwarfs
(Limoges+, 2013)
J/AJ/130/734 : Magnetic white dwarfs from SDSS DR2 and DR3
(Vanlandingham+, 2005)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+,2016)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Object name designation as JHHMM±DDMM based
on ICRS coordinates at Ep=J2000 and Eq=J2000
(J_Name)
12- 30 I19 --- GaiaDR2 The Gaia DR2 source identifier which also
could be GaiaEDR3 identifier (GaiaSourceID)
32- 60 A29 --- MWDD Identifier from MWDD database (MWDD_ID)
62- 70 F9.5 deg RAdeg Right ascension (J2000) (R.A.)
72- 80 F9.5 deg DEdeg Declination (J2000) (Decl.)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Object name designation as JHHMM±DDMM based
on ICRS coordinates at Ep=J2000 and Eq=J2000
(J_Name)
12- 16 I5 K Teff Effective temperature derived from spectral
fits analysis (Teff)
18- 21 I4 K e_Teff Uncertainty of Teff
23 A1 --- l_logg Upper limit flag of logg
25- 28 F4.2 [cm/s2] logg Logarithm of the surface gravity derived from
spectral fits analysis (logg)
30- 36 F7.5 [cm/s2] e_logg Uncertainty of logg
38- 42 F5.3 Msun M* Stellar mass derived from spectral fits
analysis (Mass)
44- 48 F5.3 Msun e_M* Uncertainty of M*
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Object name designation as JHHMM±DDMM based
on ICRS coordinates at Ep=J2000 and Eq=J2000
(J_Name)
12- 16 I5 K Teff Effective temperature derived from spectral
fits analysis (Teff)
18- 21 I4 K e_Teff Uncertainty of Teff
23- 26 F4.2 [cm/s2] logg Logarithm of the surface gravity derived from
spectral fits analysis (logg)
28- 33 F6.4 [cm/s2] e_logg Uncertainty of logg
35- 39 F5.3 Msun M* Stellar mass derived from spectral fits
analysis (Mass)
41- 46 F6.4 Msun e_M* Uncertainty of M*
48- 53 F6.2 10-7T Bp The dipole intensity Bp as magnetic field
intensity at the pole of a centred dipole at
the stellar surface (1R* from the otigin)
(Bp)
55- 56 I2 deg i The inclination angle i between the dipole
moment m ant the observer's line of sight (i)
(1)
58- 62 F5.2 --- az/R* The distance between the centre of the dipole
and the centre of the star in units of stellar
radius R* (az)
64- 69 F6.2 10-7T Bmean Mean of dipole magnetic field intensity on the
visible surface of the star
--------------------------------------------------------------------------------
Note (1): We orient the magnetic moment according to the inclination, and apply
the dipole offset by shifting the position vector accordingly.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Hardy et al., Paper I This work
Hardy et al., Paper II 2023MNRAS.520.6135H 2023MNRAS.520.6135H
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Luc Trabelsi [CDS] 20-Apr-2026