J/ApJ/898/24 Granulations of red supergiants from ASAS-SN & iPTF (Ren+, 2020)
On the granulation and irregular variation of red supergiants.
Ren Yi, Jiang B.-W.
<Astrophys. J., 898, 24 (2020)>
=2020ApJ...898...24R 2020ApJ...898...24R
ADC_Keywords: Stars, supergiant; Stars, masses; Stars, diameters;
Effective temperatures; Photometry; Optical
Keywords: Late-type stars ; Stellar pulsations ; Stellar oscillations ;
Red supergiant stars
Abstract:
The mechanisms and characteristics of the irregular variations of red
supergiants (RSGs) are studied based on the RSG samples in the Small
Magellanic Cloud (SMC), Large Magellanic Cloud (LMC), and M31. With
the time-series data from the All-Sky Automated Survey for SuperNovae
and Intermediate Palomar Transient Factory survey, we use the
continuous time autoregressive moving average model to estimate the
variability features of the light curves and their power spectral
density (PSD). The characteristic evolution timescale and amplitude of
granulations are further derived from fitting the posterior PSD with
the COR function, which is a Harvey-like granulation model. The
consistency of theoretical predictions and results is checked to
verify the correctness of the assumption that granulations on RSGs
contribute to irregular variation. The relations between granulation
and stellar parameters are obtained and compared with the results of
red giant branch (RGB) stars and Betelgeuse. It is found that the
relations are in agreement with predictions from basic physical
process of granulation and fall close to the extrapolated relations of
RGB stars. The granulations in most of the RSGs evolve at a timescale
of several days to a year with a characteristic amplitude of
10-1000mmag. The results imply that the irregular variations of RSGs
can be attributed to the evolution of granulations. When comparing the
results from the SMC, LMC, and M31, the timescale and amplitude of
granulation seem to increase with metallicity. The analytical
relations of the granulation parameters with stellar parameters are
derived for the RSG sample of each galaxy.
Description:
The time-series data are taken from the All-Sky Automated Survey for
SuperNovae (ASAS-SN) for red supergiants (RSGs) in the Large
Magellanic Cloud (LMC) and SMC and the Intermediate Palomar Transient
Factory (iPTF) survey for RSGs in M31.
The ASAS-SN consists of 24 telescopes all around the globe that
observed variable objects in the SMC and LMC at a cadence of 4-5 days
for approximately 1600 days (Shappee+ 2014, J/ApJ/788/48 ;
Kochanek+ 2017PASP..129j4502K 2017PASP..129j4502K). The ASAS-SN has magnitude limits of
g∼18 and V∼17.3 and photometric precision of 0.08mag at V∼16.
For M31, the iPTF survey monitored for about 2000 days in the g and R
bands, reaching 20.5mag at a 5σ level. We adopted the RSG sample
in our previous work (Ren+ 2019, J/ApJS/241/35), which contains 420
RSGs in M31.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 141 128 Granulation and stellar parameters of RSGs in SMC
table2.dat 141 385 Granulation and stellar parameters of RSGs in LMC
table3.dat 141 359 Granulation and stellar parameters of RSGs in M31
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See also:
II/236 : UBVR CCD survey of the Magellanic clouds (Massey+, 2002)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/AJ/123/855 : Magellanic Clouds Photometric Survey: SMC (Zaritsky+, 2002)
J/AJ/126/2867 : Red supergiants in Magellanic Clouds (Massey+, 2003)
J/AJ/128/1606 : Magellanic Clouds Photometric Survey: LMC (Zaritsky+, 2004)
J/ApJ/652/1133 : BVI photometry of NGC 4258 Cepheids (Macri+, 2006)
J/AJ/133/2393 : UBVRI phot. in 7 Local Group dwarfs galaxies (Massey+, 2007)
J/AJ/136/1221 : Most luminous LMC sources at 8µm (Kastner+, 2008)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/703/420 : Red supergiants in M31 (Massey+, 2009)
J/A+A/507/1375 : HST/ACS VI data of M31 globular clusters (Perina+, 2009)
J/ApJ/719/1784 : Yellow supergiants in the SMC (Neugent+, 2010)
J/ApJ/727/53 : Red supergiant stars in the LMC. I. (Yang+, 2011)
J/ApJ/754/35 : Red supergiant stars in the SMC. II. (Yang+, 2012)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJ/826/224 : RSG and foreground candidates in M31 (Massey+, 2016)
J/ApJ/859/73 : Variability of RSGs in M31 from iPTF (Soraisam+, 2018)
J/A+A/616/A175 : Red supergiant stars in the LMC. II. (Yang+, 2018)
J/ApJS/236/42 : Asteroseismology of ∼16000 Kepler red giants (Yu+, 2018)
J/ApJS/241/35 : Period-luminosity relations of RSGs in M33 & M31 (Ren+, 2019)
J/ApJ/889/44 : UKIRT obs. of red supergiants in M31 (Neugent+, 2020)
Byte-by-byte Description of file: table[123].dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID Galaxy ID (1)
14- 20 I7 Lsun Lbol [1884/1166440]? Bolometric luminosity
22- 25 F4.1 Msun Mass [6/33]? Mass
27- 30 I4 K Teff [1248/6764]? Surface effective temperature
32- 36 I5 Rsun Rad [56/13127]? Stellar radius
38- 41 F4.1 [cm/s2] logg [-2.4/1.8]? log of surface gravity
43- 48 F6.2 d tau [0.1/285]? Granulation timescale
estimated, CARMA (3,0) (2)
50- 55 F6.2 d e_tau [0/423]? Lower uncertainty in tau
57- 61 F5.2 d E_tau [0/25]? Upper uncertainty in tau
63- 66 F4.2 --- alpha [1.4/8]? Exponent in Equation 3 (3)
68- 71 F4.2 --- e_alpha [0/0.3]? Lower uncertainty in alpha
73- 76 F4.2 --- E_alpha [0/0.3]? Upper uncertainty in alpha
78- 83 F6.2 mmag sigma [5.5/768.1]? Characteristic amplitude of
granulation, CARMA (3,0) (2)
85- 89 F5.2 mmag e_sigma [0.03/53]? Lower uncertainty in sigma
91- 95 F5.2 mmag E_sigma [0.06/21]? Upper uncertainty in sigma
97-102 F6.2 d taueff [0.17/328]? Granulation effective
timescale, CARMA (3,0) (2)
104-109 F6.2 d e_taueff [0/481]? Lower uncertainty in tau-eff
111-115 F5.2 d E_taueff [0/24]? Upper uncertainty in tau-eff
117-122 F6.2 d taucel [0/100.5]? Granulation timescale,
celerite
124-130 F7.2 mmag sigcel [0.05/1036]? Characteristic amplitude of
granulation, celerite
132-137 F6.2 d taueffcel [0.06/177]? Granulation effective
timescale, celerite
139 A1 --- Outlier1 Outlier, tau-eff
141 A1 --- Outlier2 Outlier, sigma
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Note (1): From Yang+ 2019, J/A+A/629/A91 for SMC;
from Yang+ 2018, J/A+A/616/A175 (<[YBJ2018] NNN> in Simbad) for LMC or
from Ren+ 2019, J/ApJS/241/35 for M31.
Note (2): the Continuous-time AutoRegressive Moving Average (CARMA;
Kelly+ 2014ApJ...788...33K 2014ApJ...788...33K) model estimates the variability features
of the light curves and their power spectral densities (PSDs).
See Section 3.2.
Note (3): Equation (3) is:
P(v)= (ξσ2τgran)/(1+(2πντgran)α)
where P(v) is the total power at frequency ν, τgran is the
timescale and σgran is the amplitude; α is a positive
parameter to be fitted that characterizes the slope of the decay and
ξ is a normalization factor that depends on the value of α
(ξ=2αsin(π/α)).
See section 3.1.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Nov-2021