J/MNRAS/483/2282 p-mode-dominated subdwarf B pulsators in binaries (Reed+, 2019)
Two p-mode-dominated subdwarf B pulsators in binaries with F-star companions
observed with K2.
Reed M.D., Telting J.H., Ketzer L., Crooke J.A., Baran A.S., Vos J.,
Nemeth P., Ostensen R.H., Jeffery C.S.
<Mon. Not. R. Astron. Soc., 483, 2282-2299 (2019)>
=2019MNRAS.483.2282R 2019MNRAS.483.2282R (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Stars, subdwarf ; Stars, B-type ;
Stars, double and multiple
Keywords: stars: oscillations - subdwarfs
Abstract:
This paper presents spectroscopic and seismic analyses of two rare
hybrid pulsating subdwarf B (sdB) stars, PG 0048+091 and PG 1315-123,
which are dominated by pressure (p)-mode pulsations. These are only
the second and third sdB pulsators with detected frequency multiplets
in both the p- and g (gravity)-mode regions. This allows an
examination of the radial rotation profiles and p- and g-mode overtone
spacings. Frequency multiplets indicate that PG 1315-123 rotates
uniformly, as a solid body, while PG 0048+091 is rotating faster in
the outer envelope. g- and p-mode overtone spacings for PG 1315-123
agree with previous findings and model predictions at 237 and ∼1000s
while those for PG 0048+091 are significantly shorter at 207 and
<250s, respectively. The cause of PG 0048+091's discrepancies is
likely related to core structural differences which could be related
to progenitor mass. Spectroscopic findings show that both stars lie on
the hot end of the instability region and are most likely in
long-period binaries with main-sequence companions. Their high
temperatures challenge driving theory, which produces g-mode
pulsations only at cooler temperatures. Another challenge is the
appearance of pulsations with both driven and stochastic properties.
Such a variety of pulsation properties makes these stars very
interesting and important for understanding hot horizontal-branch
stars.
Description:
As part of our follow-up spectroscopic survey (Telting et al.
2012ASPC..452..147T 2012ASPC..452..147T) of Kepler-observed sdBV stars, we used ALFOSC at
the 2.6m Nordic Optical Telescope (see Djupvik & Andersen
2010ASSP...14..211D 2010ASSP...14..211D for a description of instrumentation), with grism
#18 and a 0.5arcsec slit providing R=2000 resolution or 2.2Å, to
obtain 5 spectra of PG 0048+091 and 12 of PG 1315-123. The instrument
was equipped with CCD8 for the first 4 spectra of PG 1315-123 and
later with CCD14 for the remaining spectra of both stars. The exposure
time was 600s, giving 53<signal to noise (S/N)<70 for PG 0048+091 and
26<S/N<71 for PG 1315-123.
The data were homogeneously reduced and analysed. Standard reduction
steps within iraf included bias subtraction, removal of pixel-to-pixel
sensitivity variations, optimal spectral extraction, and wavelength
calibration based on arc-lamp spectra. The target spectra and the
mid-exposure times were shifted to the barycentric frame of the Solar
system. A final pixel shift was applied to the velocity scale, to
account for non-perfect centring of the target in the slit, based on
slit images taken directly before and after the spectral exposures.
Objects:
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RA (2000) DE Designation(s)
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00 51 26.94 +09 21 32.9 PG 0048+091 = 2MASS J00512693+0921327
13 17 39.26 -12 32 52.4 PG 1315-123 = 2MASS J13173926-1232523
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File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 62 188 p-mode frequencies detected for PG 0048+091
table5.dat 54 18 g-mode frequencies detected for PG 0048+091
table6.dat 23 8 Lorentzian widths and power (Hi) fitted to
observations for PG 0048+091
table7.dat 44 46 p-mode frequencies detected for PG 1315-123
table8.dat 49 16 g-mode frequencies detected for PG 1315-123
table9.dat 13 4 Lorentzian widths fitted to observations of
PG 1315-123
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID p-mode frequency identifier
6- 13 F8.2 uHz Freq p-mode frequencies detected for PG 0048+091
15- 18 F4.2 uHz e_Freq ? Error on Freq
20- 29 A10 --- Stoc In this column, 'stochastic' indicates there
is a broad excess of power
31- 35 F5.3 10-3 Amp ? Amplitude (in ppt)
37- 42 F6.2 --- S/N ? Signal to noise ratio
44- 48 A5 --- mode Mode of degree and azimuthal order (l,m)
50- 62 A13 --- f2004/5 Closest frequency from Reed et al.
(2007ApJ...664..518R 2007ApJ...664..518R)
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- ID g-mode frequency identifier
4- 10 F7.3 uHz Freq g-mode frequencies detected for PG 0048+091
12- 16 F5.3 uHz e_Freq Error on Freq
18- 24 F7.2 s Period Period
26- 29 F4.2 s e_Period Error on Period
31- 35 F5.3 10-3 Amp Amplitude (in ppt)
37- 40 F4.1 --- S/N Signal to noise ratio
42- 45 A4 --- mode Mode of degree and azimuthal order (l,m)
47- 48 I2 --- n ? Relative radial indices
50- 54 F5.1 --- Dev ? Deviation from the asymptotic sequence
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 uHz Freq Frequencies associated to wide regions of
excess pulsation power
6- 9 F4.1 uHz LW1 Lorentzian width form the power spectra fit
10 A1 --- --- [/]
11- 14 F4.1 uHz LW2 ? Second Lorentzian width form the power
spectra fit
16- 19 F4.1 10-6 Hi1 Power form the power spectra fit (in ppt2)
20 A1 --- --- [/]
21- 23 F3.1 10-6 Hi2 ? Second Power form the power spectra fit
(in ppt2)
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ID p-mode frequency identifier
5- 11 F7.2 uHz Freq p-mode frequencies detected for PG 1315-123
13- 17 F5.3 uHz e_Freq ? Error on Freq
19- 28 A10 --- Stoc In this column, 'stochastic' indicates there
is a broad excess of power
30- 34 F5.3 10-3 Amp ? Amplitude (in ppt)
36- 41 F6.2 --- S/N ? Signal to noise ratio
43- 44 I2 --- mode ? Mode of degree and azimuthal order (l,m)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- ID g-mode frequency identifier
4- 10 F7.3 uHz Freq g-mode frequencies detected for PG 1315-123
12- 16 F5.3 uHz e_Freq Error on Freq
18- 23 F6.1 s Period Period
25- 27 F3.1 s e_Period Error on Period
29- 33 F5.3 10-3 Amp Amplitude (in ppt)
35- 38 F4.1 --- S/N Signal to noise ratio
40- 41 I2 --- m ? Azimuthal order, if a multiplet (1)
43- 44 I2 --- n ? Relative radial index
46- 49 F4.1 --- Dev ? Deviation from the l=1 asymptotic sequence
--------------------------------------------------------------------------------
Note (1): All identified modes are presumed to be l=1
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 uHz Freq Frequencies associated to wide regions of
excess pulsation power
6- 8 F3.1 uHz LW Lorentzian width form the power spectra fit
10- 13 F4.1 --- Hi Power form the power spectra fit (in ppt2)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 20-Jul-2022