J/ApJ/868/30 OGLE LMC-T2CEP-211 eclipsing binary LCs and RVs (Pilecki+, 2018)
The dynamical mass and evolutionary status of the Type II Cepheid in the
eclipsing binary system OGLE-LMC-T2CEP-211 with a double-ring disk.
Pilecki B., Dervisoglu A., Gieren W., Smolec R., Soszynski I.,
Pietrzynski G., Thompson I.B., Taormina M.
<Astrophys. J., 868, 30 (2018)>
=2018ApJ...868...30P 2018ApJ...868...30P
ADC_Keywords: Binaries, eclipsing; Photometry, VRI; Radial velocities;
Models, evolutionary
Keywords: binaries: eclipsing; circumstellar matter;
galaxies: individual (LMC); stars : emission-line, Be;
stars: evolution; stars: variables: Cepheids
Abstract:
We present the analysis of a peculiar W Virginis (pWVir) type II
Cepheid, OGLE-LMC-T2CEP-211 (Ppuls=9.393d), in a double-lined binary
system (Porb=242d), which shed light on virtually unknown
evolutionary status and structure of pWVir stars. The dynamical mass
of the Cepheid (first ever for a type II Cepheid) is 0.64±0.02M☉,
and the radius R=25.1±0.3R☉. The companion is a massive
(5.67M☉) main-sequence star obscured by a disk. Such a
configuration suggests a mass transfer in the system history. We found
that originally the system (Porbinit=12d) was composed of 3.5 and
2.8M☉ stars, with the current Cepheid being more massive. The
system age is now ∼200Myr, and the Cepheid is almost completely
stripped of hydrogen, with helium mass of ∼92% of the total mass. It
finished transferring the mass 2.5Myr ago and is evolving toward lower
temperatures passing through the instability strip. Comparison with
observations indicates a reasonable 2.7x10-8M☉/yr mass loss
from the Cepheid. The companion is most probably a Be main-sequence
star with T=22000K and R=2.5R☉. Our results yield a good
agreement with a pulsation theory model for a hydrogen-deficient
pulsator, confirming the described evolutionary scenario. We detected
a two-ring disk (Rdisk∼116R☉) and a shell (Rshell∼9R☉)
around the companion, which is probably a combination of the matter
from the past mass transfer, the mass being lost by the Cepheid owing
to wind and pulsations, and a decretion disk around a rapidly rotating
secondary. Our study, together with observational properties of pWVir
stars, suggests that the majority of them are products of a similar
binary evolution interaction.
Description:
Our analysis makes use of 797 measurements in the Cousins I band
collected with the Warsaw telescope at Las Campanas Observatory and
provided by the OGLE project (Soszynsk+ 2018, J/AcA/68/89).
The spectroscopic data were acquired using the MIKE spectrograph on
the 6.5m Magellan Clay telescope at Las Campanas Observatory and the
UVES spectrograph on VLT at Paranal Observatory in Chile. In total we
obtained 25 high-resolution spectra (19 MIKE + 6 UVES).
Objects:
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RA (ICRS) DE Designation(s)
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04 46 27.44 -70 59 16.7 OGLE-LMC-T2CEP-211 = OGLE LMC-T2CEP-211
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 122 134 Evolutionary models
fig2.dat 47 797 V- and I-band light curves of the Cepheid
OGLE-LMC-T2CEP-211 (data behind Figure 2)
fig7.dat 26 25 Orbital radial velocities of the Cepheid
(data behind Figure 7)
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See also:
VI/120 : High-resolution synthetic stellar library (Coelho+, 2005)
J/A+A/454/855 : Geneva photometry of W Cru (Pavlovski+, 2006)
J/AcA/58/293 : Type-II and anomalous Cepheids in LMC (Soszynski+, 2008)
J/AcA/60/91 : VI light curves of SMC type II Cepheids (Soszynski+, 2010)
J/MNRAS/413/223 : Magellanic clouds Cepheids JHKs photometry (Matsunaga+, 2011)
J/MNRAS/436/953 : OGLE-LMC-CEP-0227 RV and VI[3.6] curves (Pilecki+, 2013)
J/A+A/604/A29 : MC Type II & anomalous Cepheids PL & PR (Groenewegen+, 2017)
J/AcA/68/89 : VI light curves of SMC type II Cepheids (Soszynski+, 2018)
J/ApJ/854/109 : Photometry & spectroscopy follow-up of MWC 882 (Zhou+, 2018)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 --- q-i [0.5/1] Mass Ratio, initial
7- 11 F5.3 --- beta [0/1] Systemic Mass Loss Fraction
13- 17 F5.3 Msun Md-i [3.3/9.7] Mass, donor, initial
19- 23 F5.3 Msun Ma-i [2.1/5.2] Mass, accretor, initial
25- 30 F6.3 Msun Mtot [6.3/14.5] Mass, total
32- 37 F6.3 d Per-i [11.6/56.2] Orbital Period, initial
39- 43 F5.3 --- q [0.5/8] Mass Ratio, final fit
45- 49 F5.3 Msun Md [0.7/9.7] Mass, donor, final fit
51- 55 F5.3 [K] logTd [3.6/4.4] log Surface Temperature, donor,
final fit
57- 61 F5.3 [Lsun] logLd [2.4/3.7] log Stellar Luminosity, donor,
final fit
63- 67 F5.3 [Lsun] logRd [0.5/1.8] log Stellar Radius, donor, final fit
69- 73 F5.3 [cm/s2] loggd [1.4/4.1] log Surface Gravity, donor, final fit
75- 79 F5.3 Msun Ma [2.7/5.7] Mass, accretor, final fit
81- 85 F5.3 [K] logTa [3.9/4.4] log Surface Temperature, accretor,
final fit
87- 91 F5.3 [Lsun] logLa [1.6/3.3] log Stellar Luminosity, accretor,
final fit
93- 97 F5.3 [Lsun] logRa [0.2/0.6] log Stellar Radius, accretor, final fit
99-103 F5.3 [cm/s2] logga [4/4.6] log Surface Gravity, accretor, final fit
105-111 F7.3 d Per [24.8/186.6] Orbital Period, final fit
113-122 F10.3 --- Chi2 [9.8/100000] Chi-square statistic
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 10 F10.5 d HJD-V ? Heliocentric Julian Date; HJD-2450000
12- 17 F6.3 mag Vmag [16.6/17.4]? Warsaw/OGLE/LCO V-band magnitude
19- 23 F5.3 mag e_Vmag [0.004/0.02]? Uncertainty in Vmag
25- 34 F10.5 d HJD-Ic Heliocentric Julian Date; HJD-2450000
36- 41 F6.3 mag Icmag [15.8/16.6] Warsaw/OGLE/LCO Cousins I-band
magnitude
43- 47 F5.3 mag e_Icmag [0.004/0.01] Uncertainty in Imag
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Byte-by-byte Description of file: fig7.dat
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Bytes Format Units Label Explanations
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1- 10 F10.5 d HJD Heliocentric Julian Date; HJD-2450000
12- 18 F7.3 km/s RV1 [186/300] Orbital radial velocity of the Cepheid
20- 26 F7.3 km/s RV2 [235/249]? Orbital radial velocity of
the companion
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Oct-2019