J/A+A/656/A66 Semi-regular red giants as distance indicators (Trabucchi+, 2021)
Semi-regular red giants as distance indicators.
I. The period-luminosity relations of semi-regular variables revisited.
Trabucchi M., Mowlavi N., Lebzelter T.
<Astron. Astrophys. 656, A66 (2021)>
=2021A&A...656A..66T 2021A&A...656A..66T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Magellanic Clouds ; Photometry ; Optical
Keywords: stars: AGB and post-AGB - stars: evolution - stars: oscillations -
stars: variables: general - Magellanic Clouds - distance scale
Abstract:
Semi-regular variables (SRVs) are similar to Miras in brightness, and
they also follow PLRs, though not necessarily the same as Miras. As
potential standard candles they are more challenging than Miras due to
their smaller variability amplitudes and less regular light curves,
but they are substantially more numerous and especially promising to
probe old stellar populations.
We aim to characterize the variability of SRVs, with focus on their
connection with Miras, in order to prepare the ground for
investigating their potential as distance indicators.
We examine SRVs and Miras in the Magellanic Clouds from OGLE-III
observations, with data from Gaia and 2MASS. After cleaning the sample
from variability periods unrelated to pulsation, we classify each
source by chemical type and combination of pulsation modes. We examine
the results in terms of global photometric and pulsation properties.
We identify four SRVs groups that fit the general evolutionary
scenario predicted by theory. SRVs dominated by fundamental-mode
pulsation are very similar to Miras, especially if mono-periodic. They
further split into two sub-groups, one of which follows the same
sequence as Miras in the period-luminosity and period-amplitude
diagram, without discontinuity.
The similarities between Miras and SRVs suggest that the latter can be
adopted as complementary distance indicators to the former, thereby at
least doubling the available number of LPVs suitable for use as
distance indicators. The traditional amplitude-based separation
between Miras and SRVs is not necessarily appropriate, and a more
physically sound criterion should also involve pulsation periods.
While this would require comparatively longer time series, they are
expected to become accessible in the coming years even for weak
sources thanks to current and future large-scale surveys. The table of
reclassified LPVs is made public.
Description:
We have examined long-period variables in the Magellanic Clouds
observed by OGLE-III (Soszynski et al., 2009AcA....59..239S 2009AcA....59..239S; Soszynski
et al., 2011AcA....61..217S 2011AcA....61..217S) and classified as Miras or Semi-Regular
Variables (SRVs). Using additional information from 2MASS and Gaia
DR2, EDR3 we produced a more robust photometry-based classification by
chemical type (O- or C-rich). We thus identified the variability
periods reported in OGLE-III that are most likely due to stellar
pulsation rather than to other phenomena (e.g. long secondary periods)
or to spurious signals. For each period we identified the pulsation
mode most likely to originate it among the fundamental mode and the
first overtone mode. Periods of Miras are compatible with the
assumption that Miras pulsate only in the fundamental mode. SRVs were
classified by the number of pulsation modes and which mode is
dominant. We provide the result of this classification for 14339
sources (12416 SRVs and 1923 Miras).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 62 14339 Properties and classification of Miras and SRVs
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/AcA/59/239 : VI light curves of LMC long-period variables (Soszynski+, 2009)
J/AcA/61/217 : VI light curves of SMC long-period variables (Soszynski+, 2011)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- ID OGLE-III source ID,
OGLE-LMC-LPV-NNNNN or OGLE-SMC-LPV-NNNNN
20- 27 F8.3 d Pa [21.135/1859.0] Primary pulsation period
29- 36 F8.3 d Pb [17.75/608.6]? Secondary pulsation period (1)
38- 42 F5.3 mag Aa [0.010/4.328] Amplitude of the primary pulsation
period in the I band of OGLE
44- 48 F5.3 mag Ab [0.008/1.285]? Amplitude of the secondary
pulsation period in the I band of OGLE (1)
50 I1 --- Na [0/1] Radial order of oscillation corresponding
to the primary pulsation period (2)
52 I1 --- Nb [0/1]? Radial order of oscillation corresponding
to the secondary pulsation period (1) (2)
54 I1 --- Ka [1/3] Rank of the primary pulsation period as it
appears in the OGLE-III catalogs (3)
56 I1 --- Kb [2/3]? Rank of the secondary pulsation period as
it appears in the OGLE-III catalogs (1) (3)
58- 60 A3 --- Group Variability group according to the
classification by variability type and
pulsation periods (4)
62 A1 --- ChType Chemical type of the source based on optical and
near-infrared photometric data (5)
--------------------------------------------------------------------------------
Note (1): Pb, Ab, Nb and Kb are left blank for mono-periodic sources
Note (2): N=0 or N=1 indicate, respectively, pulsation in the fundamental mode
or in the first overtone mode
Note (3): K=1, K=2 or K=3 indicate, respectively, that a pulsation period is
appears as the primary, secondary or tertiary period in the OGLE-III
catalogs (Soszynski et al., 2009AcA....59..239S 2009AcA....59..239S; Soszynski et al.,
2011AcA....61..217S 2011AcA....61..217S)
Note (4): Variability groups code as follows:
S1 = SRV-1, SRVs pulsating only in the first overtone mode
S10 = SRV-1.0, SRVs pulsating predominantly in the first overtone
mode, with a secondary period due to the fundamental mode
S01 = SRV-0.1, SRVs pulsating predominantly in the fundamental mode,
with a secondary period due to the first overtone mode
S0 = SRV-0, SRVs pulsating only in the fundamental mode
M = Mira
The distinction between Miras and SRVs the one given in the OGLE-III
catalog, i.e. Miras have peak-to-peak I-band amplitude larger than
0.8mag, while the amplitude of SRVs is smaller
Note (5): Chemical type code as follows:
O = oxygen-rich
C = carbon-rich
U = uncertain
--------------------------------------------------------------------------------
Acknowledgements:
Michele Trabucchi, michele.trabucchi(at)unige.ch
(End) Patricia Vannier [CDS] 09-Sep-2021