J/MNRAS/491/5717 Evidenced reduced magnetic braking in polars (Belloni+, 2020)
Evidence for reduced magnetic braking in polars from binary population models.
Belloni D., Schreiber M.R., Pala A.F., Gansicke B.T., Zorotovic M.,
Rodrigues C.V.
<Mon. Not. R. Astron. Soc., 491, 5717-5731 (2020)>
=2020MNRAS.491.5717B 2020MNRAS.491.5717B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, white dwarf ; Magnetic fields ; Models ;
Optical
Keywords: methods: numerical - stars: evolution - stars: magnetic field -
novae - cataclysmic variables; white dwarfs
Abstract:
We present the first population synthesis of synchronous magnetic
cataclysmic variables, called polars, taking into account the effect
of the white dwarf (WD) magnetic field on angular momentum loss. We
implemented the reduced magnetic braking (MB) model proposed by Li, Wu
& Wickramasinghe into the Binary Stellar Evolution (BSE) code recently
calibrated for cataclysmic variable (CV) evolution. We then compared
separately our predictions for polars and non-magnetic CVs with a
large and homogeneous sample of observed CVs from the Sloan Digital
Sky Survey. We found that the predicted orbital period distributions
and space densities agree with the observations if period bouncers are
excluded. For polars, we also find agreement between predicted and
observed mass transfer rates, while the mass transfer rates of
non-magnetic CVs with periods ≳3h drastically disagree with those
derived from observations. Our results provide strong evidence that
the reduced MB model for the evolution of highly magnetized accreting
WDs can explain the observed properties of polars. The remaining main
issues in our understanding of CV evolution are the origin of the
large number of highly magnetic WDs, the large scatter of the observed
mass transfer rates for non-magnetic systems with periods ≳3h, and
the absence of period bouncers in observed samples.
Description:
We performed population synthesis of CVs composed of highly magnetized
WDs (i.e. polars) and non-magnetic WDs, and predicted period and mass
transfer rate distributions, as well as space densities for both
populations. The presented calculations are the first binary
population models that properly include reduced magnetic braking in
polars.
In order to compare our predicted orbital period distributions with
observations, we searched for all CVs with accurate orbital period
determinations from the Sloan Digital Sky Survey (SDSS). We found 199
systems, which are listed in Table B1. SDSS provides both photometric
and spectroscopic data, and allows the unambiguous identification of
CVs from hydrogen and helium emission lines. In addition, its deep
magnitude limit allows the detection of intrinsically faint systems
(Gansicke et al. 2009MNRAS.397.2170G 2009MNRAS.397.2170G), characterized by low accretion
rates, even at several scale heights above the Galactic plane. This
makes this sample one of the largest homogeneous CV samples available,
as its broad colour selection range is superior to any previous
surveys.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 60 199 CVs from SDSS with reliable orbital period
measurements
refs.dat 86 117 References for Table B1
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See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name SDSS name (HHMMSS.ss+DDMMSS.s)
20- 25 F6.1 min Porb Orbital period
27 A1 --- f_Dist [b] Flag on Dist (1)
29- 34 F6.1 pc Dist ? Distance from Bailer-Jones et al.
(2018AJ....156...58B 2018AJ....156...58B, Cat. I/347)
36- 41 F6.1 pc E_Dist ? Upper error on Dist
43- 48 F6.1 pc e_Dist ? Lower error on Dist
50- 56 A7 --- Type Cataclysmic variable type (2)
58- 60 I3 --- r_Porb Reference for Porb
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Note (1): Flag as follows:
b = There is no parallax measurement in Gaia DR2
Note (2): Type as follows:
NON-MAG = Non-magnetic cataclysmic variable (151/199)
POLAR = Polar (34/199)
IP = Intermidiate polar (4/199)
CV = Unknown cataclysmic variable type (10/199)
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Ref [1/117] Reference number
5- 23 A19 --- BibCode BibCode
25- 64 A40 --- Author Author's name
66- 86 A21 --- Com Comments
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 24-Feb-2023