J/A+A/686/A268 New binary systems in Magellanic Clouds (Rathour+, 2024)
Non-evolutionary effects on period change in Magellanic Cepheids.
I. New binary systems revealed from light travel time effect.
Rathour R.S., Hajdu G., Smolec R., Karczmarek P., Hocde V.,
Ziolkowska O., Soszynski I., Udalski A.
<Astron. Astrophys. 686, A268 (2024)>
=2024A&A...686A.268R 2024A&A...686A.268R (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Stars, double and multiple ;
Binaries, orbits ; Optical
Keywords: binaries: general - stars: variables: Cepheids
Abstract:
Period change studies offer a novel way to probe the evolution and
dynamics of Cepheids. While evolutionary period changes have been well
studied both observationally and theoretically, non-evolutionary
period changes lack a systematic and quantitative description. Here,
we deal with one such aspect of non-evolutionary period changes
related to a crucial property, namely, the binarity-based nature of a
Cepheid. With the advent of long-term photometry surveys covering
Magellanic fields, the census of classical Cepheids in binary (or
multiple) systems outside the Milky Way is timely. This may have
implications for crucial aspects such as the period-luminosity
relationship calibrations and our understanding of the nature of
Cepheid companions.
The overall objective is to have a quantitative understanding of the
full picture of non-evolutionary period changes in Cepheids to develop
a formalism to disentangle it from the secular evolutionary period
change. In the first paper in the series, we aim to conduct a
systematic search for non-evolutionary period changes to look for
Cepheids in likely binary configurations and quantify their incidence
rates in the Magellanic Clouds.
We collected more than a decade-long time-series photometry from the
publicly available, Optical Gravitational Lensing Experiment (OGLE)
survey, with more than 7200 Cepheids altogether from the Large
Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). Our sample
contains both fundamental-mode and first-overtone mode Cepheids. Then,
we calculate d the observed minus calculated (O-C) diagrams to
reveal the light-travel time effect (LTTE). Finally, we calculated the
minimum companion masses of the Cepheids and compared them with the
predictions from Cepheid population synthesis results.
In our search, out of an overall sample of more than 7200 Cepheids, we
found 52 candidate Cepheid binary systems in the LMC (30 fundamental
and 22 first-overtone mode) and 145 in the SMC (85 fundamental and 60
first-overtone mode). The majority of the sample is characterized by
orbital periods of 2000-4000d and eccentricities of 0.2-0.5.
Moreover, we report two candidates in each galaxy with the Cepheid
likely existing with a giant companion. The incidence rate ratio for
SMC to LMC calculated from our sample is in agreement with binary
Cepheid population synthesis predictions.
In our attempt to quantify the non-evolutionary period change
connected with the LTTE, our systematic search has enriched the
Cepheid binary sample by a factor of about 2 in both galaxies. The
future spectroscopic follow-up can confirm the binarity nature of our
sample and constrain the orbital parameters.
Description:
We have applied the modified Hertzsprung method to analyze period
changes of classical Cepheids in the Magellanic Clouds based on OGLE
data. This resulted in O-C diagrams of more than 7200 Cepheids. Our
systematic search for periodic O-C features resulted in a sample of
197 candidates for binary Cepheids.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 143 52 List of LMC binary Cepheid candidates with
their orbital parameters
tablea2.dat 143 145 List of SMC binary Cepheid candidates with
their orbital parameters
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See also:
J/AcA/65/297 : OGLE4 LMC and SMC Cepheids (Soszynski+, 2015)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Mode [F 1O] Pulsation mode
4- 9 A6 --- Sample Sample (1)
11- 14 I04 --- Target Target name (NNNN) for
OGLE LMC-CEP-NNNN in LMC,
OGLE SMC-CEP-NNNN in SMC
16- 20 A5 --- n_Target Note (2)
22- 23 I2 --- Fitorder Fit order
25- 35 F11.8 d Ppul Pulsation period
37- 40 I4 d Porb Orbital period
42- 44 I3 d e_Porb Orbital period error
46- 50 I5 d T0 Time of periastron passage
52- 54 I3 d e_T0 Time of periastron passage error
56- 61 F6.3 --- e Eccentric anomaly
63- 67 F5.3 --- e_e Eccentric anomaly error
69- 74 F6.3 AU asini asini semi-major axis
76- 80 F5.3 AU e_asini asini semi-major axis error
82- 85 I4 deg omega Argument of periastron
87- 89 I3 deg e_omega Argument of periastron error
91- 97 F7.3 d/Myr PCR Linear period-change rate
99-103 F5.3 d/Myr e_PCR Linear period-change rate error
105-111 F7.3 km/s K Semi-amplitude of the expected radial
velocity variation,
113-118 F6.2 km/s e_K Semi-amplitude of the expected radial
velocity variation error
120-126 F7.3 Msun f(m) Mass function
128-133 F6.3 Msun e_f(m) Mass function error
135-139 F5.1 Msun Mc Mass of the companion
141-143 F3.1 Msun Mcep Mass of the Cepheid
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Note (1): Strong candidates constitute the gold sample. The remaining ones are
the marginal candidates referred to as the bronze sample.
Note (2): Notes as follows:
d = peculiar mass function candidates
a = additional low amplitude variability
b = sub-harmonic signal
* = additional radial mode
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 06-Aug-2024