J/MNRAS/478/1425 Single-mode OGLE Cepheids additional modes (Suveges+, 2018)
Investigating light-curve modulation via kernel smoothing.
II. New additional modes in single-mode OGLE classical Cepheids.
Suveges M., Anderson R.I.
<Mon. Not. R. Astron. Soc., 478, 1425-1441 (2018)>
=2018MNRAS.478.1425S 2018MNRAS.478.1425S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, variable
Keywords: methods: statistical - stars: oscillations -
stars: variables: Cepheids - Magellanic Clouds -
methods: data analysis
Abstract:
Detailed knowledge of the variability of classical Cepheids, in
particular their modulations and mode composition, provides crucial
insight into stellar structure and pulsation. However, tiny
modulations of the dominant radial-mode pulsation were recently found
to be very frequent, possibly ubiquitous in Cepheids, which makes
secondary modes difficult to detect and analyse, since these
modulations can easily mask the potentially weak secondary modes. The
aim of this study is to re-investigate the secondary mode content in
the sample of OGLE-III and OGLE-IV single-mode classical Cepheids
using kernel regression with adaptive kernel width for pre-whitening,
instead of using a constant-parameter model. This leads to a more
precise removal of the modulated dominant pulsation, and enables a
more complete survey of secondary modes with frequencies outside a
narrow range around the primary. Our analysis reveals that significant
secondary modes occur more frequently among first overtone Cepheids
than previously thought. The mode composition appears significantly
different in the Large and Small Magellanic Clouds, suggesting a
possible dependence on chemical composition. In addition to the
formerly identified non-radial mode at P2~=0.6...0.65P1
(0.62-mode), and a cluster of modes with near-primary frequency, we
find two more candidate non-radial modes. One is a numerous group of
secondary modes with P2~=1.25P1, which may represent the
fundamental of the 0.62-mode, supposed to be the first harmonic of an
l ∈ {7, 8, 9} non-radial mode. The other new mode is at P2
~=1.46P1, possibly analogous to a similar, rare mode recently
discovered among first overtone RR Lyrae stars.
Description:
Our study uses the OGLE-II, OGLE-III, and OGLE-IV I-band photometric
time series data of classical Cepheids. Observations were taken in
1997-2000 (OGLE-II, Udalski et al., 1997AcA....47..319U 1997AcA....47..319U), in
2001-2009 (OGLE-III, Soszynski et al. 2008, Cat. J/AcA/58/163), and
in 2010-2015 (OGLE-IV, ongoing; Udalski et al.,
2015AcA....65....1U 2015AcA....65....1U), with two long gaps (up to about 300 and 700d,
respectively) and instrumentation changes between the three phases of
the survey. Observations were conducted using the 1.3-m Warsaw
telescope at Las Campanas Observatory in Chile.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
smc.dat 219 736 Significant secondary modes in the SMC
lmc.dat 212 897 Significant secondary modes in the LMC
--------------------------------------------------------------------------------
See also:
J/AcA/65/297 : OGLE4 LMC and SMC Cepheids (Soszynski+, 2015)
Byte-by-byte Description of file: smc.dat lmc.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Id Identifier from OGLE catalogue name
OGLE SMC-CEP-NNNN in Simbad for smc.dat,
OGLE SMC-CEP-NNNN in Simbad for lmc.dat
6- 14 F9.7 d Per1a ?=- OGLE-III period
16- 24 F9.7 d Per1b ?=- OGLE-IV period
26- 76 A51 --- Rema OGLE-III remarks
78-116 A39 --- Remb OGLE-IV remarks
118-127 F10.6 d P2 ?=- Secondary period found in this study
129-138 E10.7 --- FAP ?=- False alarm probability
140-149 A10 --- SecMode Secondary mode of the star
151-219 A69 --- CandMode Possible modes for the secondary
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Jun-2021