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Subaru Near-infrared Imaging Polarimetry of Misaligned Disks around the SR 24
Hierarchical Triple System
*
Satoshi Mayama
1
, Sebastián Pérez
2
, Nobuhiko Kusakabe
3,4
, Takayuki Muto
5
, Takashi Tsukagoshi
4
, Michael L. Sitko
6
,
Michihiro Takami
7
, Jun Hashimoto
3,4
, Ruobing Dong
8
, Jungmi Kwon
9
, Saeko S. Hayashi
4,10
, Tomoyuki Kudo
11
,
Masayuki Kuzuhara
3,4
, Katherine Follette
12
, Misato Fukagawa
4
, Munetake Momose
13
, Daehyeon Oh
14
,
Jerome de Leon
15
, Eiji Akiyama
16
, John P. Wisniewski
17
, Yi Yang
3,4
, Lyu Abe
18
, Wolfgang Brandner
19
,
Timothy D. Brandt
20
, Michael Bonnefoy
21
, Joseph C. Carson
22
, Jeffrey Chilcote
23
, Thayne Currie
11
, Markus Feldt
19
,
Miwa Goto
24
, Carol A. Grady
25,26,27
, Tyler Groff
28
, Olivier Guyon
3,11,29
, Yutaka Hayano
4,10,11
, Masahiko Hayashi
30
,
Thomas Henning
19
, Klaus W. Hodapp
31
, Miki Ishii
4
, Masanori Iye
4
, Markus Janson
32
, Nemanja Jovanovic
33
,
Ryo Kandori
3
, Jeremy Kasdin
34
, Gillian R. Knapp
34
, Julien Lozi
11
, Frantz Martinache
35
, Taro Matsuo
36
,
Michael W. McElwain
25
, Shoken Miyama
37
, Jun-Ichi Morino
4
, Amaya Moro-Martin
38
, Takao Nakagawa
39
,
Tetsuo Nishimura
11
, Tae-Soo Pyo
10,11
, Evan A. Rich
17
, Eugene Serabyn
40
, Hiroshi Suto
3,4
, Ryuji Suzuki
4
,
Naruhisa Takato
10,11
, Hiroshi Terada
4
, Christian Thalmann
41
, Daigo Tomono
11
, Edwin L. Turner
34,42
, Makoto Watanabe
43
,
Toru Yamada
39
, Hideki Takami
4,10
, Tomonori Usuda
4,10
, Taichi Uyama
9
, and Motohide Tamura
3,4,9
1
The Graduate University for Advanced Studies, SOKENDAI, Shonan Village, Hayama, Kanagawa 240-0193, Japan; mayama_satoshi@soken.ac.jp
2
Universidad de Santiago de Chile, Av. Libertador Bernardo O’Higgins 3363, Estación Central, Santiago, Chile
3
Astrobiology Center, NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
4
National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
5
Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-8677, Japan
6
Center for Extrasolar Planetary Systems, Space Science Institute, 1120 Paxton Avenue, Cincinnati, OH 45208, USA
7
Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan
8
Department of Physics & Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
9
Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
10
Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
11
Subaru Telescope, NAOJ, NINS, 650 North A’ohoku Place, Hilo, HI 96720, USA
12
Amherst College, Department of Physics and Astronomy, AC#2244, PO Box 5000, Merrill Science Center, 15 Mead Drive, Amherst, MA 01002-5000, USA
13
College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito 310-8512, Japan
14
National Meteorological Satellite Center, 64-18 Guam-gil, Gwanghyewon-myeon, Jincheon-gun, Chungbuk, Republic of Korea
15
Department of Astronomy, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
16
Institute for the Advancement of Higher Education, Hokkaido University, Kita 17, Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-0817, Japan
17
H. L. Dodge Department of Physics & Astronomy, University of Oklahoma, 440 W Brooks Street, Norman, OK 73019, USA
18
Laboratoire Lagrange (UMR 7293), Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Coted’azur, 28 avenue Valrose, F-06108 Nice Cedex 2, France
19
Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
20
Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530, USA
21
Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France
22
Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424, USA
23
Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556, USA
24
Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 München, Germany
25
Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD, 20771, USA
26
Eureka Scientific, 2452 Delmer, Suite 100, Oakland CA 96002, USA
27
Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
28
NASA Goddard Space Flight Center, Greenbelt, MD, USA
29
Steward Observatory, University of Arizona, 933 N Cherry Ave., Tucson AZ 85719, USA
30
JSPS Bonn Office, Wissenschaftszentrum, Ahrstrasse 58, D-53175 Bonn, Germany
31
Institute for Astronomy, University of Hawaii, 640 N. A’ohoku Place, Hilo, HI 96720, USA
32
Department of Astronomy, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden
33
Jet Propulsion Laboratory, California Institute of Technology, M/S 171-113 4800 Oak Grove Drive Pasadena, CA 91109 USA
34
Department of Astrophysical Science, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544, USA
35
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
36
Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyamacho, Toyonaka, Osaka 560-0043, Japan
37
Hiroshima University, 1-3-2 Kagamiyama, Higashihiroshima, Hiroshima 739-8511, Japan
38
Space Telescope Science Institute (STScI), 3700 San Martin Drive, Baltimore, MD 21218, USA
39
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
40
Jet Propulsion Laboratory, California Institute of Technology, M/S 183-900 4800 Oak Grove Drive Pasadena, CA 91109, USA
41
Swiss Federal Institute of Technology (ETH Zurich), Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
42
Kavli Institute for Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568, Japan
43
Department of Cosmosciences, Hokkaido University, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
Received 2019 June 17; revised 2019 November 14; accepted 2019 November 14; published 2019 December 12
The Astronomical Journal, 159:12 (10pp), 2020 January https://doi.org/10.3847/1538-3881/ab5850
© 2019. The American Astronomical Society.
*Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
Original content from this work may be used under the terms
of the Creative Commons Attribution 3.0 licence. Any further
distribution of this work must maintain attribution to the author(s)and the title
of the work, journal citation and DOI.
1
Abstract
The SR 24 multistar system hosts both circumprimary and circumsecondary disks, which are strongly misaligned
with each other. The circumsecondary disk is circumbinary in nature. Interestingly, both disks are interacting, and
they possibly rotate in opposite directions. To investigate the nature of this unique twin disk system, we present 0 1
resolution near-infrared polarized intensity images of the circumstellar structures around SR 24, obtained with
HiCIAO mounted on the Subaru 8.2 m telescope. Both the circumprimary disk and the circumsecondary disk are
resolved and have elongated features. While the position angle of the major axis and radius of the near-IR (NIR)
polarization disk around SR 24S are 55°and 137 au, respectively, those around SR 24N are 110°and 34 au,
respectively. With regard to overall morphology, the circumprimary disk around SR 24S shows strong asymmetry,
whereas the circumsecondary disk around SR 24N shows relatively strong symmetry. Our NIR observations confirm
the previous claim that the circumprimary and circumsecondary disks are misaligned from each other. Both the
circumprimary and circumsecondary disks show similar structures in
12
CO observations in terms of its size and
elongation direction. This consistency is because both NIR and
12
CO are tracing surface layers of the flared disks. As
the radius of the polarization disk around SR 24N is roughly consistent with the size of the outer Roche lobe, it is
natural to interpret the polarization disk around SR 24N as a circumbinary disk surrounding the SR 24Nb–Nc system.
Unified Astronomy Thesaurus concepts: Polarimetry (1278)
1. Introduction
Observationally, there are many young binary stars hosting a
circumprimary disk misaligned with respect to either a
circumsecondary disk, a circumbinary disk, or a binary orbital
plane (e.g., HK Tau, Jensen & Akeson 2014; L1551 NE,
Takakuwa et al. 2017; GG Tau, Aly et al. 2018; IRS 43, Brinch
et al. 2016; GW Ori, Czekala et al. 2017; HD 98800, Kennedy
et al. 2019). These circumprimary and circumsecondary disks
are directly imaged as two single disks. More recently, another
type of young misaligned disk is beginning to be observed.
They are inner disks misaligned with respect to outer disks both
surrounding a single transitional object (e.g., HD 142527,
Casassus et al. 2015; HD 100453, Benisty et al. 2017, van der
Plas et al. 2019, HD 143006, Benisty et al. 2018; HD 135344B,
Stolker et al. 2016; DoAr 44, Casassus et al. 2018; J1604,
Mayama et al 2012; Mayama et al. 2018). Even in an earlier
stage of protostar evolution, a warped disk around the protostar
IRAS 04368+2557 was discovered with the Atacama Large
Millimeter/submillimeter Array (ALMA; Sakai et al. 2019).
Some promising mechanisms that have been claimed to
address theoretically the origin of inner disks misaligned with
respect to outer disks are as follows: (1)the rotation axis of the
disk system is misaligned with respect to the magnetic field
direction (e.g., Ciardi & Hennebelle 2010);(2)the anisotropic
accretion of gas with different rotational axes (e.g., Bate 2018);
and (3)a massive planet misaligned with respect to an outer
disk tilting an inner disk (e.g., Nealon et al. 2019; Zhu 2019).
In the third mechanism, the planet is assumed to be sufficiently
massive to open a gap in the disk. Such planets can become
misaligned with respect to an outer disk through secular
interaction with an external misaligned companion (Lubow &
Martin 2016; Martin et al. 2016), or through precessional
resonances (Owen & Lai 2017). In both cases, the inner disk
(within the planet/companion orbital radius)might become
aligned to the orbital plane of the planet, thus becoming
misaligned with respect to the outer disk.
Among misaligned disks observed thus far, ALMA observa-
tions have shed light on SR 24, the target of this study, because
Fernández-López et al. (2017)suggest that the circumprimary disk
is strongly misaligned (108°)with respect to the circumsecondary
disk, and both disks possibly rotate in opposite directions as
observed from Earth, in projection. Here, the target of this study is
introduced.
SR 24, also known as HBC262, is located in the Ophiuchus
star-forming region. Gaia DR2 reported that SR 24 is located at
a distance of 114 pc (Gaia Collaboration et al. 2018).SR24isa
hierarchical multiple system composed of a primary, SR 24S,
and a secondary, SR 24N. SR 24S is classified as a K2-type
classII T Tauri star and has a mass of >1.4M
e
(Cohen &
Kuhi 1979; Correia et al. 2006). SR 24N, located 5 2 north at a
position angle (PA)of 348°(Reipurth & Zinnecker 1993),is
classified as an M0.5 type classII T Tauri star (Cohen &
Kuhi 1979). Simon et al. (1995)observed that SR 24N itself is
a binary system of SR 24Nb and SR 24Nc with a projected
separation of 0 197. The eccentricity of the orbit of SR 24Nb
and SR 24Nc is derived as -
+
0
.64 0.10
0.13 (Schaefer et al. 2018). The
spectral type and mass of SR 24Nb are K4–M4 and 0.61M
e
,
respectively (Correia et al. 2006), whereas those of SR 24Nc
are K7–M5 and 0.34M
e
, respectively (Correia et al. 2006).
Nüernberger et al. (1998)observed the dust emission
associated with SR 24S, whereas for SR 24N, they derived
only an upper limit of the flux density based on their 1.3 mm
map. At 10μm, which is an indicator of warm circumstellar
dust in the inner part of the disk, both southern and northern
components showed roughly equal emission. Thus, the 10μm
measurements indicate that the inner part of the disk around SR
24N is still present, whereas the nondetection of 1.3mm
emission from SR 24N indicates a lack of cold circumstellar
dust in the outer part of the disk. Nüernberger et al. (1998)
suggested that this was likely due to enhanced disk accretion or
destruction caused by the presence of SR 24Nc.
Andrews & Williams (2005)presented high-resolution
aperture synthesis images from the submillimeter array of the
1.3 mm continuum and CO J=2–1 line emission from the
disks around the components of SR 24. In their image, SR 24S
is associated with a circumstellar disk detected both in the
continuum and CO line emission with properties typical of
those around single T Tauri stars, whereas SR 24N is only
detected in CO line emission and not in the continuum. Based
on their observations, they suggested that SR 24N was
surrounded by at least one circumstellar disk and a circumbin-
ary gas disk, presumably with a dynamically carved gap.
Andrews & Williams (2007)presented a high-spatial-
resolution submillimeter 1330μm continuum image of SR 24
using SMA. They modeled the circumstellar disk around SR
24S by using broadband spectral energy distribution and
submillimeter visibilities to derive the physical parameters of
2
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
the disk. Their results show that the outer radius, inclination,
and PA of the circumprimary disk around SR 24S are
-
+
5
00 175
500 au, 57°, and 25°, respectively.
Fernández-López et al. (2017)reported ALMA data and
detected 1.3 mm continuum emission from SR 24N for the first
time in this wavelength domain. The mass associated with the
SR 24S and SR 24N disks is derived to be 0.025 M
e
and
4×10
−5
M
e
, respectively. In addition, their
12
CO(2–1)
ALMA and SMA velocity cubes show three main features:
(i)a gas reservoir extending north–northwest of SR 24N, (ii)a
bridge of gas connecting SR 24N with SR 24S disks, and (iii)
an elongated and blueshifted feature due southwest of SR 24S.
In the near-infrared (NIR), Mayama et al. (2010)resolved
both circumprimary and circumsecondary disks around SR 24S
and SR 24N, respectively. Their 0 1 observation detected a
bridge of infrared emission connecting the two disks and a long
spiral arm extending from the circumprimary disk.
Zhang et al. (2013)conducted H
2
NIR imaging observation
to search for molecular hydrogen emission line objects.
Although their observation covers an area of ∼0.11 deg
2
toward the L1688 core in the ρOphiuchi molecular cloud
including the area where SR 24 is located, they do not detect
any emission from SR 24.
As SR 24 is a complex hierarchical triple system, there are
still many unanswered questions in this regard. Therefore, in
this paper, we present high-resolution NIR polarimetric images
of SR 24 south and north as data. High-resolution polarimetric
imaging is a powerful tool to study the structure of
protoplanetary disks. The rest of this paper is organized as
follows. Observations and data reduction procedures are
described in Section 2. The results and discussion are presented
in Sections 3and 4, respectively. Section 5summarizes the
conclusions.
2. Observations and Data Reduction
We performed polarimetry in the Hband (1.6 μm)toward SR
24 using the high-resolution imaging instrument HiCIAO
(Hodapp et al. 2006;Tamuraetal.2006)with a dual-beam
polarimeter mounted on the Subaru 8.2m Telescope on 2011
August 2. These observations are part of the high-contrast
imaging survey, Strategic Explorations of Exoplanets and Disks
with Subaru (SEEDS; Tamura 2009). The polarimetric observa-
tion mode acquires o-rays and e-rays simultaneously, and images
with a fieldofviewof10″×20″with a pixel scale of
9.5mas pixel
−1
. SR 24S was observed without an occulting
mask in order to image the innermost region around the central
star. The exposures were sequentially performed at four position
angles (P.A.s)of the half-wave plate, which are P.A.=0°,45°,
22°. 5, and 67°. 5, in one rotation cycle to measure the Stokes
parameters. The integration time per wave plate position was 15 s,
and the total integration time of the polarization intensity
(hereafter PI)image was 1140 s. The adaptive optics system
(AO 188; Hayano et al. 2010)provides a diffraction-limited and
almost stable stellar point-spread function (PSF).
The Image Reduction and Analysis Facility software (IRAF
44
)
was used for data reduction. We follow the polarimetric data
reduction technique described in Hashimoto et al. (2011)
and Muto et al. (2012), in which the standard approach for
polarimetric differential imaging (Hinkley et al. 2009)was
adopted. By subtracting two images of extraordinary and
ordinary rays at each wave plate position, we obtained +Q,
−Q,+U, and −Uimages, from which 2Qand 2Uimages were
obtained through another subtraction to eliminate the remaining
aberration. The PI was then calculated by =+QU
P
I22
.
The instrumental polarization of HiCIAO at the Nasmyth
platform was corrected by following Joos et al. (2008).
3. Results
3.1. SR 24S Circumprimary Disk
The H-band PI image of SR 24S after subtracting the
polarized halo is presented in Figure 1(a). The polarized signal
corresponds to stellar light scattered off the surface of small
dust particles which are mixed with the circumstellar gas. Disk
inner regions around SR 24S have appeared at 0 1. The bridge
and spiral arm, which were detected in Mayama et al. (2010),
are not detected with this observation, possibly owing to
limited observation time which provided a modest signal-to-
noise ratio (S/N). While the CIAO image in Mayama et al.
(2010)revealed the outer part of the outer disk, the relatively
inner part of the outer disk is mainly observed at this time in
this PI image with HiCIAO. The circumstellar structure around
SR 24S has elongated features both to the northeast and
southeast directions.
Along the major axis, the PI on the northeast side is 7.6 times
stronger than that on the southwest side at around 0 25 from
the primary source. Along the minor axis, the PI on the
southeast side is 3.7 times stronger than that on the northwest
side at around 0 5 from the primary source. These show strong
asymmetry along both the major and minor axes.
Figure 1(b)shows H-band polarization vectors superposed
on the PI image. Although most of the circumprimary
structures around SR 24S show a centrosymmetric vector
pattern, the north–northwest and southwest circumstellar
structures do not show such a pattern. Considering the
separation between SR 24N and SR 24S, the deviation from
a centrosymmetric polarization angle is probably because the
circumstellar disk around SR 24S is partly illuminated also by
SR 24N. The illumination from a relatively far star is reported
around other young multiple systems. Krist et al. (1998), Hioki
et al. (2011), and Gledhill & Scarrott (1989)suggested that the
northern portion of the FS Tau circumbinary disk is illuminated
by Haro 6–5 B located 20″(2800 au)west of the FS Tau
binary. Many polarization vectors around the FS Tau binary
deviate from the larger centrosymmetric pattern in their maps.
In addition, the azimuth angles of these two regions at the
northwest and southwest of SR 24S are consistent with the disk
regions connecting the north bridge and southwest spiral arm
shown in Mayama et al. (2010). Therefore, these undetected
bridge and arm structures might induce local polarization
structures that deviate from the larger centrosymmetric pattern,
disturbing the centrosymmetric polarization vector pattern
around SR 24S.
Figure 2(a)shows the radial surface brightness profile of SR
24S along the major axis. In the northeast direction, the surface
brightness along the major axis decreases as r
−1.8
from 0 4to
12 and decreases as r
−1.1
from 1 3to1 4. In the southwest
direction, the surface brightness along the major axis decreases
as r
−1.1
from 0 4to0 6 and decreases as r
−0.3
from 0 7to
08. Figure 2(b)shows the radial profile of the surface
44
IRAF is distributed by the National Optical Astronomy Observatory, which
is operated by the Association of Universities for Research in Astronomy, Inc.,
under cooperative agreement with the National Science Foundation.
3
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
brightness along the minor axis. In the northwest direction, the
surface brightness along the minor axis decreases as r
−1.7
from
02to0 4 and decreases as r
−0.02
from 0 5to0 7. In the
southeast direction, the surface brightness along the major axis
decreases as r
−1.8
from 0 2to1 0. The typical error in the
power-law index is ∼0.1.
The radial profiles in the northeast direction along the major
axis show a change of slope beyond 1 2. Thus, our observations
indicate that the NIR polarization disk seen in scattered light has a
radius of 1 2, while there are possibly structures that are not
illuminated by the central star beyond this NIR polarization
radius. The derived semimajor axis is called “NIR polarization
radius”in this paper. The P.A. of this NIR circumprimary disk is
derived to be 55°as it is the brightest angle.
3.2. SR 24N Circumsecondary Disk
Figure 1(c)shows the H-band PI image of SR 24N after
subtracting the polarized halo. Figure 1(d)shows the polarization
vectors overlaid on the PI image of SR 24N. SR 24Nb–Nc is not
spatially resolved with our Subaru observations. This is because
our 0 1 resolution is not sufficiently high to resolve SR 24Nb–Nc.
Based on an orbit calculated by Schaefer et al. (2018),the
separation between SR 24Nb–Nc at the time of our observations in
2011 should be much smaller than 93.73±1.58 mas, which was
the closest in time to our Subaru observations and observed by
Keck in 2014. In this paper, we consider SR 24Nb and SR 24Nc
together as SR 24N and plot SR 24N with a green plus sign in
Figures 1(c)and (d).
All of the circumsecondary structures around SR 24N show a
centrosymmetric vector pattern in contrast to SR 24S. There are
elongated emissions in the east–west direction. This elongated
direction is nearly consistent with the CIAO observations.
Figure 2(d)shows the radial surface brightness profile of SR
24N along the major axis. The error bars shown in Figure 2
represent the calculated standard deviation. In the western
direction, the surface brightness along the major axis decreases
as r
−2.1
from 0 1to0 3 and decreases as r
−1.0
from 0 3to0 8.
In the east direction, the surface brightness along the major axis
decreases as r
−2.6
from 0 1to0 3 and decreases as r
−0.7
from
03to0 8. Figure 2(e)shows the radial profile of the surface
brightness along the minor axis. In the south direction, the
surface brightness along the minor axis decreases as r
−1.6
from
01to0 3. In the north direction, the surface brightness along
the minor axis decreases as r
−2.0
from 0 1to0 3.
Figure 1. H-band Subaru+HiCIAO images of SR 24. Here, north is up, and east is to the left. The length of the bar indicates 0 5. The plus sign denotes the position
of the central star, SR 24S, for (a)and (b), and SR 24N for (c)and(d). SR 24Nb and SR 24Nc are not separately plotted because they are not resolved. (a)PI image of
SR 24S. The field of view(FOV)is 2 8×2 8. (b)H-band polarization vectors superposed on the PI image of SR 24S. The vector directions indicate the angles of
polarization. The vector’s lengths are arbitrary. The FOV is 2 8×2 8. (c)PI image of SR 24N. The FOV is 1 6×1 6. (d)H-band polarization vectors superposed
on the PI image of SR 24N. The vector directions indicate the angles of polarization. The vector’s lengths are arbitrary. The FOV is 1 6×1 6.
4
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
The radial profiles in the east and west directions along the
major axis show a change of slope beyond 0 3. Thus, our
observations indicate that the NIR polarization disk seen in
scattered light has a radius of 0 3, while there are possibly
structures that are not illuminated by the central star beyond
this NIR polarization radius. The P.A. of the circumsecondary
disk is derived as 110°.
Figure 2(c)shows the azimuth-averaged radial surface
brightness profile of SR 24S and SR 24N. The surface
brightness of SR 24S decreases as r
−1.5
from 0 2to1 0. The
surface brightness of SR 24N decreases as r
−2.1
from 0 1to
03. The typical uncertainty of the measured power-law index
is ∼0.1. As shown in Figure 2(c), the azimuth radial surface
brightness of SR 24N has a steeper profile than that of SR 24S.
Our observations also show that the SR 24S disk is more
spatially extended than the SR 24N disk.
4. Discussion
4.1. Circumbinary Disk Surrounding SR 24Nb–Nc
There appears to be a marginal detection of an arc-shaped
structure emanating from the SR 24N circumsecondary disk as
indicated by the blue dashed line in Figure 1(d). It begins at the
west side of the SR 24N disk, extending north first, then
curving to the northeast. The polarization vectors in the region
of this arc structure face the central star SR 24N, indicating that
this arc is not an artifact but a real structure illuminated by the
central star and is physically connected to the outer edge of the
circumsecondary disk associated with SR 24N. As this
morphology is symmetric to the bridge emanating from the
east side of the SR 24N disk also observed using both CIAO
and Hubble Space Telescope (HST), this morphology might be
attributed to binary formation.
Adopting the separation between Nb–Nc to be 0 16 as
measured by HST observations and the mass ratio, q, of 0.56
based on Correia et al. (2006), the size of the outer Roche lobe
and the distance from SR 24Nb to the L2 point are derived as
031 and 0 26 in radius, respectively. As the measured radius,
03, of the polarization disk around SR 24N is roughly
consistent with the computed size of the outer Roche lobe, it is
natural to interpret the polarization disk around SR 24N
detected with HiCIAO as a circumbinary disk surrounding the
SR 24Nb–Nc system. The measured average distance to the
arc-shaped structure is 0 26, and it is almost consistent with
Figure 2. Radial surface brightness profiles of SR 24 south and SR 24 north. (a)The radial surface brightness profile of the primary source SR 24 south along the
major axis. NE and SW radial profiles are averaged over 45°<P.A.<65°and 225°<P.A.<245°, respectively. (b)Radial surface brightness profile of the primary
source SR 24 south along the minor axis. Azimuth radial profile is also displayed. NW and SE radial profiles are averaged over 315°<P.A.<335°and 135°<P.
A.<155°, respectively. (c)Azimuthally averaged normalized surface brightness of SR 24 south and SR 24 north. (d)Radial surface brightness profile of the
secondary source SR 24 north along the major axis. West and east radial surface brightness profiles are averaged over 275°<P.A.<295°and 95°<P.A.<
115°,
respectively. (e)Radial surface brightness profile of the secondary source SR 24 north along the minor axis. Azimuth radial profile is also displayed. South and north
radial profiles are averaged over 185°<P.A.<205°and 5°<P.A.<25°, respectively.
5
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
the computed distance to the L2 point. Thus, it is a plausible
explanation that this arc-shaped structure is consistent with
material leaking out the back door via the L2 point. Such a
leakage of material occurs naturally from disks in binaries. The
bridge structure emanating from the eastern side of the SR 24N
disk can be observed to emanate beyond the size of the outer
Roche lobe, indicating that the bridge structure is not attributed
to the binary formation between Nb and Nc, but is attributed to
the binary formation of the SR 24S–N system.
Schaefer et al. (2018)derived the P.A. and inclination of the
SR 24Nb–Nc orbit to be 72°.0 and 132°.1, respectively, by
calculating the orbit. As shown in Figure 3, Fernández-López
et al. (2017)derived the P.A. and inclination of the secondary
SR 24N CO disk to be 297°±5°and 121°±17°,
respectively. Our derived NIR polarization disk P.A. of 110°
is roughly consistent with the P.A. of the CO gas disk. This
consistency is because both NIR and CO are tracing surface
layers of the disks. Therefore, NIR and CO both traced the
circumbinary disk surrounding SR 24Nb–Nc.
The continuum emission detected around SR 24N is
unresolved by the ALMA observations at a resolution of 150
[mas](Fernández-López et al. 2017). As its continuum disk
size is much smaller than the SR 24Nb–Nc orbit, Schaefer et al.
(2018)suggested that the continuum emission is likely from a
circumstellar disk surrounding either Nb or Nc and is not from
a circumbinary disk around SR 24Nb–Nc. Based on an orbit
calculation by Schaefer et al. (2018), the angular semimajor
axis of SR 24N is 181 [mas](+83, −30). By using the estimate
from Artymowicz & Lubow (1994), namely, the outer edge of
a circumprimary disk should be truncated at around
r=0.3–0.5 times the semimajor axis, a maximum outer edge
of the circumstellar disk is 90.5 [mas]. This size of the disk was
not able to be resolved by the ALMA observation shown in
Fernández-López et al. (2017). Therefore, the current estimate
of circumstellar disk edge agrees with the estimate from
Artymowicz & Lubow (1994).
4.2. Asymmetric Disk
Andrews et al. (2010)presented SMA 880μm continuum
observations of SR 24S with a resolution of 0 37 and resolved
a disk. Their inset image of the SR 24S disk revealed a resolved
central emission cavity with an apparent brightness enhance-
ment to the northeast direction. According to their model fitting
to the visibility at 880μm, the cavity radius is 32 au (Andrews
et al. 2010)or 29 au (Andrews et al. 2011).
Based on cycle 0 ALMA 0.45 mm continuum observations,
van der Marel et al. (2015)modeled the SR 24S disk and
derived that its disk P.A., inclination, and cavity radius are 20°,
45°, and 25 au, respectively. They also presented a
12
CO
channel map for SR 24S, which indicates that the southwest
side is moving to the far side, whereas the northeast side is
moving to the near side. The zero-moment
12
CO J=6–5 line
map in Figure 1 of their paper shows the CO disk extending to
the northeast direction. The P.A. and size of their
12
CO disk
are consistent with the corresponding values of our NIR
polarization disk. Similar to the case of SR 24N, this
consistency is because both NIR and CO are tracing surface
layers of the disks.
Fernández-López et al. (2017)presented 1.3 mm continuum
images at a resolution of 0 18 obtained from ALMA cycle 1 and
2 observations. The ring-shaped disk associated with SR 24S is
resolved, and its semimajor axis, semiminor axis, P.A., and
inclination are 0 70±006, 0 50±006, 212°±3°,and
44°±6°, respectively. They also derived the P.A. and inclination
of
12
CO disks around both sources as shown in Figure 3.Forthe
primary, SR 24S, the P.A. and inclination are 218°±2°and
70°±5°, respectively. Based on their measurements and
analysis, the SR 24S disk has its nearest side to the east and the
SR 24N disk has its nearest side to the north. They suggest that
the SR 24S disk rotates in the counterclockwise direction, whereas
the SR 24N disk rotates in the clockwise direction.
The cycle 2 ALMA 1.3 mm continuum images of SR 24
with a resolution of 0 18 are reported by Pinilla et al. (2017).
Figure 3. Subaru image superimposed on ALMA image (Fernández-López et al. 2017)of SR 24. Left:
12
CO integrated emission from SR 24S overlaid on top of the
Subaru PI scattered-light image of SR 24S (gray color). Redshifted emission is integrated from 7.3 to 12.4 km s
−1
(red contours at 27%, 42%, 69%, and 96% of the
peak emission); near-zero-velocity emission is integrated from 2.2 to 4.1 km s
−1
(yellow contours at 50%, 65%, 80%, and 95% of the peak emission); blueshifted
emission is integrated from −6.0 to 1.6 km s
−1
(blue contours, same as redshifted contours). Right:
12
CO integrated emission from SR 24S overlaid on top of the
Subaru PI scattered-light image of SR 24S (gray color). Redshifted emission is integrated from 6.6 to 10.5 km s
−1
(red contours at 20%, 30%, and 40% of the map
peak emission located at SR 24S); zero-velocity emission is integrated from 5.3 to 6.0 km s
−1
(yellow contours at 50% and 60% of the map peak emission);
blueshifted emission is integrated from −0.3 to 2.2 km s
−1
(blue contours at 50% and 60% of the map peak emission).
6
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
The 1.3 mm continuum images of the SR 24S disk are
described by a ring-like emission with a central cavity. Fitting
by Pinilla et al. (2017)showed that the P.A., inclination, and
peak radius for the SR 24S disk are 24°. 30, 46°. 31, and 0 3,
respectively. They detected
13
CO and C
18
O(J=2–1)emis-
sion, both of which peaked at the center of the millimeter cavity
associated with the SR 24S disk. Neither continuum nor gas
emission from SR 24N is detected. A potential asymmetric
shape on the SR 24S disk is inferred from the analysis in the
visibility domain. In particular, both the north and south–
southeast directions of SR 24S have strong emission in contrast
with other directions.
Whereas the millimeter cavity around SR 24S with a radius of
∼03 has been resolved by SMA and ALMA, it is not detected
in our Subaru image. Thus, SR 24S possesses one of the
“missing cavities”in NIR scattered light (Dong et al. 2012).
Companion–disk interaction combined with dust filtration has
been put forward as a likely explanation for such cavities (Zhu
et al. 2012;Dongetal.2015). Planet-opened gaps can reach a
variety of depth depending on the planet mass, disk viscosity,
and scale height (Fung et al. 2014). It is possible for gaps to be
only modestly depleted in ∼micron-sized dust, generally well
coupled to the gas, and not prominent in scattered light. On the
other hand, dust filtration (Rice et al. 2006)at the outermost gap
edge can effectively stop millimeter-sized dust from entering the
gap. Thus, such particles are drained in the inner disk, resulting
in a prominent cavity in millimeter continuum emission.
Photoevaporation may also open cavities in disks (e.g.,
(Alexander & Armitage 2007). However, a low accretion rate
onto the star (<1e−8M
e
yr
−1
)is expected in this scenario
(Owen et al. 2012; Ercolano & Pascucci 2017), due to its inside-
out nature. SR 24S has a high accretion rate of 10
−7.15
M
e
yr
−1
derived from the Paschen hydrogen recombination lines (Natta
et al. 2006),anditscavityisunlikelytobeproducedby
photoevaporation.
Figure 2(b)shows that the radial surface brightness decreases
first around 0 5 then stops decreasing until 0 7 along the minor
northwest axis. Figure 2(a)shows that the radial surface brightness
decreases first around 0 75 then increases until 0 9alongthe
major southwest axis. According to Figures 2(a)and (b),both
northwest and southwest radial surface brightness show a steeper
slope whereas other directions show a gradual slope. The
azimuthal direction of this NIR decrement structure is consistent
with that observed in the submillimeter in Pinilla et al. (2017).A
possible origin of this asymmetry is discussed in the next
subsection.
4.3. Inner Disk Misaligned with Respect to an Outer Disk as an
Origin of Asymmetry
Recently, Pinilla et al. (2019)reported ALMA band 3
observations at 2.75 mm for the SR 24S disk with an angular
resolution of 0 11×0 09 and detected an inner disk. They
observed that the inner disk emission is likely dominated by
dust thermal emission instead of free–free emission. However,
it is unclear whether the inner disk is misaligned with respect to
the outer disk because the inner disk parameters such as P.A.,
inclination, and gas kinematic information are not derived.
Nixon et al. (2013)and Facchini et al. (2013)proposed a
mechanism to generate a misaligned disk system: a binary on
an inclined orbit with respect to its disk can break the
circumbinary disk into inner and outer components, and cause
the inner disk to press, resulting in a time-variant mutual
inclination between the two disks.
By comparing Subaru NIR and ALMA dust and gas
observations with 3D smoothed particle hydrodynamics
(SPH)simulation shown in Facchini et al. (2018), we interpret
that the SR 24S disk asymmetry is caused by the misaligned
inner disk with respect to the outer disk based on the following
two points.
(i)Scattering image: there are two constricted regions toward
the north and southwest directions (P.A.=0°and 225°)in the
Subaru NIR scattering image. While both sides of the
circumprimary disk along the minor axis show mostly a
symmetric distribution in the 1.3 mm dust continuum, only the
northeastern and southern sides of the circumprimary disk in
the NIR scattering image are bright. This morphology can be
observed in Figure 4(b).
(ii)Dust continuum: the S/N at both 0.45 and 1.3 mm
continuum images of the SR 24S disk shows that the west side
Figure 4. 3D SPH simulation figures of misaligned inner and outer disks cited from Facchini et al. (2018). In all panels, the misalignment angle between the inner and
outer disk is ∼30°. All panels are rotated 128°in the counterclockwise direction from their original P.A. in Facchini et al. (2018)in order to adjust to the P.A. of SR 24
derived from ALMA CO observation. (a)A schematic of the disk 3D structure cited from Figure 9(b)in Facchini et al. (2018). Radial distances are not to scale. (b)
Scattered-light observation at 1.65μm of the hydro model cited from Figure 9(j)in Facchini et al. (2018). Inclination angle is 45°.
7
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
of the ring has a slightly weaker emission compared with the
east side of the ring (Pinilla et al. 2017). This asymmetry is
consistent with Figure 13(j)in Facchini et al. (2018).
As compared in (i)and (ii), the stages of the 3D
SPH simulations shown in Facchini et al. (2018)shared
common features with the observed images in the NIR and
continuum. This consistency between observations and simula-
tion suggests that the observed asymmetry on the circumprim-
ary disk SR 24S in NIR scattered light might be affected by the
inner disk being misaligned with respect to the outer disk.
A comparison between the 3D SPH simulation by Facchini
et al. (2018)and observations also provides constraints on the
inclination of the inner disk. We compared Figure 8 for the
ξ=74°case and Figure 9 for the ξ=30°case in Facchini
et al. 2018.(ξdenotes the misalignment angle between the
inner and outer disks). In particular, the (i),(j),(k), and (l)
panels in both Figures 8 and 9, which have an outer disk
inclination of 45°, are compared because previous submilli-
meter dust continuum observations revealed that the SR 24S
outer disk has an inclination of approximately 45°. The outer
disk shows a relatively axisymmetric structure, with two
azimuthal regions of lower surface brightness for the ξ=74°
cases. For the ξ=30°cases, in contrast, the outer disk shows a
relatively nonaxisymmetric structure, with one side being much
brighter than the other. In addition, there are relatively less
clear signatures of pairs of azimuthal intensity decrements at
near-symmetric locations in contrast with the ξ=74°cases. As
our NIR image has a similar asymmetric structure, the
inclination of the inner disk can be constrained to close to
ξ=30°cases in contrast with ξ=74°cases.
Finally, the leading formation mechanism of the misaligned
inner disk with respect to the outer disk around SR 24S is
discussed here. As introduced in Section 1, there are mainly
three promising mechanisms that claim to address theoretically
the origin of misalignment between an inner and an outer disk:
(1)the rotation axis of the disk system is misaligned with the
magnetic field direction; (2)the anisotropic accretion of gas
with different rotational axes; and (3)a massive planet
misaligned with respect to an outer disk tilting an inner disk.
To discuss the leading formation mechanism of an inner disk
misaligned with respect to outer disks in the SR 24S case and
provide constraints to these mechanisms, we list some
observational results below.
As discussed above, the misalignment angle between the
inner and outer disks can be constrained to close to ξ=30°in
contrast with ξ=74°. The third mechanism starts from a small
misalignment angle between an inner and outer disk and
eventually produces a large misalignment angle, whereas the
first mechanism can only produce small misaligned angles.
Therefore, the first mechanism can be ruled out. Although no
direct imaging observations have detected a companion inside
the SR 24S cavity so far, the third mechanism triggered by an
undetected massive companion embedded in the cavity could
possibly tilt the inner disk of SR 24S. Subsequently, the second
mechanism cannot be ruled out because the mass accretion rate
of SR 24S and SR 24N is 10
−7.15
and 10
−6.90
M
e
yr
−1
derived
from the Paschen hydrogen recombination lines (Natta et al.
2006), respectively. In addition, the circumprimary disk around
SR 24S has a bridge and spiral arm. According to the numerical
simulation in Mayama et al. (2010), fresh material streams
along the spiral arm in which gas is replenished from a
circummultiple reservoir and the bridge corresponds to gas
flow and a shock wave caused by the collision of gas rotating
around the primary and secondary stars. These structures, in
particular the bridge, might contribute to the tilting of the outer
disk around SR 24S. This is because the bridge is physically
connecting the two circumprimary and circumsecondary disks,
which are strongly misaligned with one another. While it is
difficult to provide further constraints on the origin of
misalignment between the inner and outer disk with the
currently available data, these mechanisms can be revealed
using very-high-resolution observations such as ALMA in the
future.
4.4. Binarity of SR 24S
The similarities between SR 24S and HD 142527 suggest the
presence of a relatively massive companion. Price et al. (2018)
and Lacour et al. (2016)demonstrated that the presence of such
a companion can address various structures observed in the HD
142527 disk including a cavity, horseshoe, and so on.
Therefore, we discuss the possibility that SR 24S may have
an unseen companion.
As introduced in Section 1, the spectral type L2 and a
luminosity of 12.9L
e
of SR 24S are adopted here from Greene
& Meyer (1995). Although the extinction correction of
Av=13.7 mag is large, this would not change the conclusion.
It is because that would not move SR 24S horizontally, but
vertically, on the Hertzsprung–Russell diagram. Figure 5shows
that SR 24S is plotted along with the pre-main-sequence
evolution tracks derived in Tognelli et al. (2011). This figure
shows that the mass is slightly larger than 2.0M
e
. Because
pre-main-sequence (PMS)star properties in both Greene &
Meyer (1995)and Pecaut & Mamajek provide T
eff
=5000 K
and 5040 K, respectively, log t=3.70 is a reliable parameter.
The mass of SR 24S is derived as 2.0M
e
in Greene &
Meyer (1995).
Consequently, taking all the uncertainties into account, it
would be hard for SR 24S to have an equal-mass binary star.
This is because the combined light would be cooler than a K2
star if SR 24S and its binary both have 0.9M
e
, for example.
However, it is possible for SR 24S to have a companion which
is smaller than 0.4M
e
, as the smaller mass companion would
be from 1/10 to 1/20 the luminosity of the more massive star,
SR 24S.
Furthermore, Pinilla et al. (2016)and Pinilla et al. (2019)
used ALMA observation data and demonstrated that a massive
planet (<5M
jup
)could be present in the cavity of SR 24S while
they excluded the possibility of existence of more massive
planets (5M
jup
)in the cavity of SR 24S. The misalignment
between the inner and outer disk surrounding SR 24S discussed
in Section 4.3 might be attributed to this embedded massive
companion. According to 3D numerical simulations by Nealon
et al. (2018), for a planet massive enough to carve a gap, a disk
is separated into two components and the gas interior and
exterior to the planet orbit evolve separately, forming an inner
and outer disk. Due to the inclination of the planet, a warp
develops across the planet orbit such that there is a relative tilt
and twist between these disks.
5. Summary
We have conducted high-resolution H-band polarimetric
imaging observations of the enigmatic SR 24 triple system. The
main conclusions are as follows:
8
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
1. The circumprimary disk associated with SR 24S is resolved
and has elongated features both to the northeast and
southeast directions. The P.A. and radius of the NIR
polarization disk around SR 24S are 55°and 1 2,
respectively. The P.A. and size of the
12
CO disk are
consistent with the corresponding values of our NIR
polarization disk. As the stages of the 3D SPH simulations
shared common features with the observed images in the
NIR, continuum, and
12
CO, this consistency suggests that
the observed asymmetry on the circumprimary disk might be
duetotheinnerdiskbeingmisalignedwithrespecttothe
outer disk.
2. The circumsecondary disk associated with SR 24N is
resolved and has elongated features in the east–west
direction. The P.A. and radius of the NIR polarization
disk around SR 24N are 110°and 0 3, respectively. The
sizes and P.A.s derived from the NIR polarization and
12
CO gas observations are consistent with each other. As
the radius of the polarization disk around SR 24N
measured to be 0 3 is roughly consistent with the
computed size of the outer Roche lobe, it is natural to
interpret the polarization disk around SR 24N detected
with HiCIAO as a circumbinary disk surrounding the SR
24Nb–Nc system.
3. In the radial direction, the surface brightness of SR 24S
and SR 24N decreases as r
−1.5
from 0 2to1 0 and r
−2.1
from 0 1to0 3, respectively. The azimuth radial surface
brightness of SR 24N has a steeper profile than that of SR
24S. Our observations also show that the SR 24S disk is
more spatially extended than the SR 24N disk.
4. As an overall morphology, the circumprimary disk
around SR 24S shows strong asymmetry, whereas the
circumsecondary disk around SR 24N shows relatively
strong symmetry. Both the circumprimary and circumse-
condary disks show similar structures to the
12
CO gas
disk in terms of size and elongation direction. This
consistency is because both NIR and
12
CO are tracing
surface layers of the flared disks. Our NIR observations
confirm the previous claim made through 0 2 submilli-
meter observations that the circumprimary disk is
misaligned with respect to the circumsecondary disk.
We thank the telescope staff and operators of the Subaru
Telescope for their assistance. We sincerely thank the referee
for giving us all these very useful and constructive suggestions,
which greatly improved the paper. M.T. is partially supported
by JSPS KAKENHI grant Nos. 18H05442 and 15H02063. This
work was supported in part by SOKENDAI(The Graduate
University for Advanced Studies)and JSPS KAKENHI grant
Nos. 25800107. Y.Y. is supported by NAOJ ALMA Scientific
Research Grant Numbers 2019-12A.
ORCID iDs
Satoshi Mayama https://orcid.org/0000-0002-3424-6266
Sebastián Pérez https://orcid.org/0000-0003-2953-755X
Takashi Tsukagoshi https://orcid.org/0000-0002-
6034-2892
Michael L. Sitko https://orcid.org/0000-0003-1799-1755
Michihiro Takami https://orcid.org/0000-0001-9248-7546
Jun Hashimoto https://orcid.org/0000-0002-3053-3575
Ruobing Dong https://orcid.org/0000-0001-9290-7846
Jungmi Kwon https://orcid.org/0000-0003-2815-7774
Tomoyuki Kudo https://orcid.org/0000-0002-9294-1793
Katherine Follette https://orcid.org/0000-0002-7821-0695
Misato Fukagawa https://orcid.org/0000-0003-3500-2455
Munetake Momose https://orcid.org/0000-0002-3001-0897
Daehyeon Oh https://orcid.org/0000-0003-2691-804X
Eiji Akiyama https://orcid.org/0000-0002-5082-8880
John P. Wisniewski https://orcid.org/0000-0001-9209-1808
Timothy D. Brandt https://orcid.org/0000-0003-2630-8073
Figure 5. SR 24S primary star plotted as a green square along with the pre-main-sequence evolution tracks of Tognelli et al. (2011).
9
The Astronomical Journal, 159:12 (10pp), 2020 January Mayama et al.
Jeffrey Chilcote https://orcid.org/0000-0001-6305-7272
Thayne Currie https://orcid.org/0000-0002-7405-3119
Olivier Guyon https://orcid.org/0000-0002-1097-9908
Yutaka Hayano https://orcid.org/0000-0003-4937-4233
Klaus W. Hodapp https://orcid.org/0000-0003-0786-2140
Masanori Iye https://orcid.org/0000-0002-5634-7770
Markus Janson https://orcid.org/0000-0001-8345-593X
Nemanja Jovanovic https://orcid.org/0000-0001-5213-6207
Ryo Kandori https://orcid.org/0000-0003-2610-6367
Gillian R. Knapp https://orcid.org/0000-0002-9259-1164
Frantz Martinache https://orcid.org/0000-0003-1180-4138
Michael W. McElwain https://orcid.org/0000-0003-
0241-8956
Shoken Miyama https://orcid.org/0000-0001-5017-180X
Amaya Moro-Martin https://orcid.org/0000-0001-
9504-8426
Takao Nakagawa https://orcid.org/0000-0002-6660-9375
Tae-Soo Pyo https://orcid.org/0000-0002-3273-0804
Evan A. Rich https://orcid.org/0000-0002-1779-8181
Hiroshi Terada https://orcid.org/0000-0002-7914-6779
Christian Thalmann https://orcid.org/0000-0002-1664-2177
Makoto Watanabe https://orcid.org/0000-0002-3656-4081
Tomonori Usuda https://orcid.org/0000-0001-9855-0163
Taichi Uyama https://orcid.org/0000-0002-6879-3030
Motohide Tamura https://orcid.org/0000-0002-6510-0681
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