J/A+A/686/A304 EX Hya spectra (Beuermann+, 2024)
High-resolution spectroscopy of the intermediate polar EX Hydrae.
II. The inner disk radius,
Beuermann K., Reinsch K.
<Astron. Astrophys. 686, A304 (2024)>
=2024A&A...686A.304B 2024A&A...686A.304B (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, spectroscopic ; Binaries, cataclysmic ;
Spectra, ultraviolet ; Optical
Keywords: binaries: eclipsing - stars: fundamental parameters -
novae, cataclysmic variables - stars: individual: EX Hydrae -
white dwarfs - X-rays: stars
Abstract:
EX Hya is one of the best studied, but still enigmatic intermediate
polars. We present phase-resolved blue VLT/UVES high-resolution
(λ/{DELTA}λ~=16.000) spectra of EX Hya taken in January
2004. Our analysis involves a unique decomposition of the Balmer line
profiles into the spin-modulated line wings that represent streaming
motions in the magnetosphere and the orbital-phase modulated line core
that represents the accretion disk. Spectral analysis and tomography
show that the division line between the two is solidly located at
|vrad|~=1200km/s, defining the inner edge of the accretion disk at
rin≃7x109cm or ∼10R1 (WD radii). This large central hole allows
an unimpeded view of the tall accretion curtain at the lower pole with
a shock height up to hsh∼1R1 that is required by X-ray and optical
observations. Our results contradict models that advocate a small
magnetosphere and a small inner disk hole. Equating rin with the
magnetospheric radius in the orbital plane allows us to derive a
magnetic moment of the WD of µ1~=1.3x1032G.cm3 and a surface
field strength B1∼0.35MG. Given a polar field strength Bp~<1.0MG,
optical circular polarization is not expected. With an accretion rate
dM/dt=3.9x10-11M☉/yr, the accretion torque is
Gacc~=2.2x1033g.cm2/s2. The magnetostatic torque is of similar
magnitude, suggesting that EX Hya is not far from being synchronized.
We measured the orbital radial-velocity amplitude of the WD,
K1=58.7±3.9km/s, and found a spin-dependent velocity modulation as
well. The former is in perfect agreement with the mean velocity
amplitude obtained by other researchers, confirming the published
component masses M1~=0.79M☉ and M2~=0.11M☉ .
Description:
EX Hya was observed in service mode with the Ultraviolet and Visual
Echelle Spectrograph (UVES) at the Kueyen (UT2) unit of the ESO Very
Large Telescope (VLT), Paranal/Chile, on January 23 and 26, 2004,
continuously for 2.58 and 2.50h, respectively. A total of 26 and 25
spectra were taken. Exposure times were 300s with dead times of
typically 60s between exposures, due to readout and overhead. The
resulting orbital phase resolution is {DELTA}φ98∼0.061 and the
spin-phase resolution {DELTA}φ67 ∼0.090. Spectra in the blue and
red arms were obtained simultaneously; the red spectra were
extensively discussed by Beuermann & Reinsch (2008A&A...480..199B 2008A&A...480..199B).
Objects:
---------------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------------
12 52 24.22 -29 14 55.9 EX Hydrae = V* EX Hya
---------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
phases.dat 88 51 Orbital and spin phases of the spectra
vradcaii.dat 37 16 CaII8498.020 radial velocities
vradfei.dat 37 16 FeI4957.596 radial velocities
vradsii.dat 37 16 Si3905.527 radial velocities
vrhbeta.dat 51 51 Radial velocities from the Hbeta line
vrhgamma.dat 51 51 Radial velocities from the Hgamma line
fits/* . 51 *Individual spectra
--------------------------------------------------------------------------------
Note on fits/*: The files z23*.fts and z26*.fts represent the total of 51
reduced and calibrated UVES spectra of EX Hydra taken on 23 and 26 Jan 2004.
Exposure time was 300s, with the center of the bins given as UTC, TDB, and
98-min and 67-min phases. The original spectral resolution was reduced by
rebinning from a pixel size of 0.030Å and a FWHM of 0.175Å to 0.300Å
pixels.
--------------------------------------------------------------------------------
See also:
J/MNRAS/461/1576 : EX Hya mid-eclipse timings (Echevarria+, 2016)
Byte-by-byte Description of file: phases.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- no Exposure number
5- 14 A10 "date" Obs.date Date
16- 17 I2 h Obs.h UTC hours
19- 20 I2 min Obs.m UTC minutes
22- 27 F6.3 s Obs.s UTC seconds
29- 33 F5.3 --- AM Airmass
36- 48 F13.7 d BJD Barycentric Julian Date, TDB (BJD-2400000)
51- 58 F8.5 --- phi98 Orbital phase (G1)
61- 68 F8.5 --- phi67 Spin phase (G2)
71 I1 --- min Flag (1)
74 I1 --- max Flag (1)
78- 88 A11 --- FileName Filename of the spectrum, in subdirectory fits
--------------------------------------------------------------------------------
Note (1): Numbers in columns min and max indicate which spectra have been used
to calculate the spin max and the spin min spectra no. 1, 2, or 3.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: vradcaii.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 4 I2 --- i Index
7- 12 F6.4 --- phiHS Orbital phase (G1)
14- 19 F6.1 km/s vobs Measured radial velocity (G3)
21- 26 F6.1 km/s e_vobs Error of vobs
30 I1 --- w Weight
32- 37 F6.1 km/s vmod Modelled radial velocity (1)
--------------------------------------------------------------------------------
Note (1): CaII8498.020 radial velocities
Number of iterations = 37
chi2 = 6.55 for 7 dof with chi2red = 0.936
j parameter(j) value (j) error(j)
1 K_2 (km/s) 0.3571627E+03 0.49690E+01
2 phi_0 0.9130039E-02 0.26192E-02
3 gamma (km/s) 0.5775098E+02 0.37947E+01
--------------------------------------------------------------------------------
Byte-by-byte Description of file: vradfei.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 4 I2 --- i Index
7- 12 F6.4 --- phiHS Orbital phase (G1)
14- 19 F6.1 km/s vobs Measured radial velocity (G3)
21- 26 F6.1 km/s e_vobs Error of v_obs
30 I1 --- w Weight
32- 37 F6.1 km/s vmod Modelled radial velocity (2)
--------------------------------------------------------------------------------
Note (2): FeI4957.596 radial velocities
Number of iterations = 27
chi2 = 6.49 for 7 dof with chi2red = 0.927
j parameter(j) values(j) error(j)
1 K_2 (km/s) 0.3463258E+03 0.41838E+01
2 phi_0 0.1090891E-01 0.22195E-02
3 -gamma (km/s) 0.5951126E+02 0.31623E+01
--------------------------------------------------------------------------------
Byte-by-byte Description of file: vradsii.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 4 I2 --- i Index
7- 12 F6.4 --- phiHS Orbital phase (G1)
14- 19 F6.1 km/s vobs Measured radial velocity (G3)
21- 26 F6.1 km/s e_vobs Error of vobs
30 I1 --- w Weight
32- 37 F6.1 km/s vmod Modelled radial velocity (3)
--------------------------------------------------------------------------------
Note (3): Si3905.527 radial velocities
Number of iterations = 42
chi2 = 8.50 for 8 dof with chi2red = 1.062
j parameter(j) value(j) error(j)
1 K_2 (km/s) 0.3459556E+03 0.55760E+01
2 phi_0 0.6979389E-02 0.28480E-02
3 -gamma (km/s) 0.5428391E+02 0.41432E+01
--------------------------------------------------------------------------------
Byte-by-byte Description of file: vrhbeta.dat vrhgamma.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Obs.date Observation date
13- 14 I2 --- Seq Sequence number within obs. night
18- 23 F6.1 km/s vrad Radial velocity (G4)
25- 29 F5.1 km/s e_vrad Error of vrad
32- 38 F7.4 --- phi98 Orbital phase (G1)
41- 47 F7.4 --- phi67 Spin phase (G2)
51 I1 --- incl [0/1] Flag (G4)
--------------------------------------------------------------------------------
Global notes:
Note (G1): linear orbital ephemeris of Hellier & Sproats (1992IBVS.3724....1H 1992IBVS.3724....1H)
Note (G2): quadratic ephemeris of Mauche et al. (2009IBVS.5876....1M 2009IBVS.5876....1M)
Note (G3): Narrow-line radial velocities from Fig. 1 and Table 1.
The narrow-line spectra of Jan23 and 26, 2004 were averaged and
fitted with Eq. 1: v_rad = K_2 sin(2pi*phi_HS + phi_0) + gamma.
gamma = -58.2 km/s is adopted.
Note (G4): Radial velocities from the Hbeta and Hgamma line wings in the left
two panels of Fig. 7. The radial velocities were obtained from fitting the
line wings of Hbeta and Hgamma outside the central disk-related spectral
component within about ±1200 km/s. gamma = -58.2 km/s is adopted.
The entries with incl=0 are affected by eclipse effects and excluded from
the fits. Corrected phases are carried on from Jan 23 to Jan 26, 2004.
--------------------------------------------------------------------------------
Acknowledgements:
Klaus Reinsch, klaus.reinsch(at)uni-goettingen.de
References:
Beuermann & Reinsch, Paper I 2008A&A...480..199B 2008A&A...480..199B
(End) Patricia Vannier [CDS] 05-Jun-2024