J/ApJ/851/132 ∼30yr of opt. spectroscopy & Vmag obs. of GW Ori (Czekala+, 2017)
The architecture of the GW Ori young triple-star system and its disk: dynamical
masses, mutual inclinations, and recurrent eclipses.
Czekala I., Andrews S.M., Torres G., Rodriguez J.E., Jensen E.L.N.,
Stassun K.G., Latham D.W., Wilner D.J., Gully-Santiago M.A., Grankin K.N.,
Lund M.B., Kuhn R.B., Stevens D.J., Siverd R.J., James D., Gaudi B.S.,
Shappee B.J., Holoien T.W.-S.
<Astrophys. J., 851, 132 (2017)>
=2017ApJ...851..132C 2017ApJ...851..132C
ADC_Keywords: Stars, double and multiple; Spectra, optical; Radial velocities;
Photometry, VRI
Keywords: protoplanetary disks ; stars: fundamental parameters ;
stars: individual (GW Ori) ; stars: pre-main sequence
Abstract:
We present spatially and spectrally resolved Atacama Large
Millimeter/submillimeter Array (ALMA) observations of gas and dust
orbiting the pre-main-sequence hierarchical triple-star system GW Ori.
A forward modeling of the 13CO and C18O J=2-1 transitions permits
a measurement of the total stellar mass in this system,
5.29±0.09M☉, and the circumtriple disk inclination,
137.6°±2.0°. Optical spectra spanning a 35yr period were
used to derive new radial velocities and, coupled with a spectroscopic
disentangling technique, revealed that the A and B components of
GW Ori form a double-lined spectroscopic binary with a period of
241.50±0.05d; a tertiary companion orbits that inner pair with a
period of 4218±50d. Combining the results from the ALMA data and the
optical spectra with three epochs of astrometry in the literature, we
constrain the individual stellar masses in the system
(MA∼2.7M☉, MB∼1.7M☉, MC∼0.9M☉) and find strong
evidence that at least one of the stellar orbital planes (and likely
both) is misaligned with the disk plane by as much as 45°. A
V-band light curve spanning 30yr reveals several new ∼30-day eclipse
events 0.1-0.7mag in depth and a 0.2mag sinusoidal oscillation that is
clearly phased with the AB-C orbital period. Taken together, these
features suggest that the A-B pair may be partially obscured by
material in the inner disk as the pair approaches apoastron in the
hierarchical orbit. Lastly, we conclude that stellar evolutionary
models are consistent with our measurements of the masses and basic
photospheric properties if the GW Ori system is ∼1Myr old.
Description:
GW Ori was observed with the ALMA interferometer on 2015 May 14
(program ID 2012.1.00496.S), with 37 of the 12m main array antennas
configured to span baselines of 23-558m.
The ALMA correlator was set up to process data in four spectral
windows: 220.426 and 230.450GHz to observe the 13CO and 12CO J=2-1
transitions, around 219.763GHz to observe the C18O J=2-1 transition
and the continuum in a 1.875GHz range around 231.956GHz.
The observations cycled between GW Ori and the quasar J0510+1800 with
a 7-minute cadence. See section 2.1 for further details.
GW Ori was monitored spectroscopically at the Harvard-Smithsonian
Center for Astrophysics for more than 35yr, beginning in 1981
November. A total of 203 usable spectra were gathered through 2009
April using three nearly identical echelle spectrographs with a
resolving power of R∼35000 mounted on three different telescopes: the
1.5m Tillinghast reflector at the Fred L. Whipple Observatory (Mount
Hopkins, AZ), the 4.5m equivalent Multiple Mirror Telescope (also on
Mount Hopkins) before conversion to a monolithic mirror, and
occasionally on the 1.5m Wyeth reflector at the Oak Ridge Observatory
(in the town of Harvard, MA). See section 2.2 for further explanations.
We have assembled a high-cadence light curve of GW Ori covering a
∼30yr time span by drawing from several ongoing photometric surveys
and archival observations.
Photoelectric UBVR observations of GW Ori were obtained at Mount
Maidanak Observatory in Uzbekistan from 1987 to 2003.
See section 2.3.1.
Both telescopes of the Kilodegree Extremely Little Telescope (KELT)
project use a broad R-band filter. GW Ori was located in KELT-South
field 05 and was observed 2889 times from UT 2010 February 28 until UT
2015 April 09, with a median uncertainty of 0.005 mag.
See section 2.3.2.
The two observatory (Las Campanas, Chile, and Haleakala, Maui) of
All-sky Automated Survey (ASAS) observed GW Ori in the V band from UT
2001 March 11 until UT 2009 November 29, obtaining 480 observations
with a median per-point uncertainty of 0.036mag.
See section 2.3.3.
ASAS-SN surveys the entire sky down to V∼17mag every ∼2days. Hosted by
the Las Cumbres Observatory at Mount Haleakala, Hawaii, and the Cerro
Tololo Inter-American Observatory in Chile. ASAS-SN obtained 799
observations of GW Ori from UT 2014 December 16 until UT 2017 March
15, with a typical per-point error of 0.01mag.
See section 2.3.4.
Objects:
-----------------------------------------------------------------------
RA (ICRS) DE Designation(s) Inner_Per Outer_Per
-----------------------------------------------------------------------
05 29 08.39 +11 52 12.7 GW Ori = HD 244138 (P=241.5) (P=4246)
-----------------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 34 284 Heliocentric RV measurements of GW Ori
table3.dat 31 4708 Photometric measurements of GW Ori
--------------------------------------------------------------------------------
See also:
B/wds : The Washington Visual Double Star Catalog (Mason+ 2001-2014)
B/eso : ESO Science Archive Catalog (ESO, 1991-2018)
VI/110 : Final Merged Log of IUE Observations (NASA-ESA, 2000)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+AS/124/75 : Multiple star catalogue (MSC) (Tokovinin 1997-1999)
J/AJ/118/1043 : Herbig Ae/Be stars catalog (Herbst+, 1999)
J/AJ/121/2124 : λ Ori pre-main-sequence stars photom. (Dolan+, 2001)
J/AJ/123/387 : λ Ori star-forming region VRI photom. (Dolan+, 2002)
J/ApJS/147/305 : IUE atlas of pre-main-sequence stars (Valenti+, 2003)
J/A+A/461/183 : Variability of classical T Tauri (Grankin+, 2007)
J/MNRAS/389/869 : Multiplicity among bright stellar systems (Eggleton+, 2008)
J/ApJ/720/1118 : i-band photometry of HAT-P-16 (Buchhave+, 2010)
J/ApJ/744/121 : Far-UV spectroscopy of T Tau stars (Yang+, 2012)
J/ApJ/761/123 : KELT-1 photometry and spectroscopy follow-up (Siverd+, 2012)
J/ApJ/771/129 : Submillimetric Class II sources of Taurus (Andrews+, 2013)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/AJ/151/146 : IRS sp. with features of crystalline silicates (Chen+, 2016)
J/ApJ/834/142 : Gould's Belt Distances Survey (GOBELINS) II. (Kounkel+, 2017)
J/ApJ/844/103 : Orbit alignment in triple stars (Tokovinin, 2017)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d HJD [44919/57863.7] Heliocentric Julian Date;
HJD-2400000 (1)
12- 16 F5.2 km/s RVelA [12/39.5] Radial velocity of primary
18- 22 F5.2 km/s e_RVelA [0.4/11] The 1σ uncertainty in RVelA
24- 28 F5.2 km/s RVelB [-10/50] Radial velocity of secondary
30- 34 F5.2 km/s e_RVelB [1/38] The 1σ uncertainty in RVelB
--------------------------------------------------------------------------------
Note (1): Observations up to HJD 2,454,926.6573 were obtained with the
Digital Speedometers (DS; now decommissioned) and the remainder
with Tillinghast Reflector Echelle Spectrograph (TRES).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d HJD [47031.4/57829.8] Heliocentric Julian Date;
HJD-2400000
12- 16 F5.2 mag Vmag [9.4/30] Apparent V band magnitude
18- 22 F5.3 mag e_Vmag [0.001/0.2]?=0 The 1σ uncertainty in Vmag
24- 31 A8 --- Tel Telescope used in the observation (1)
--------------------------------------------------------------------------------
Note (1): Telescope as follows:
Maidanak = Mount Maidanak Observatory in Uzbekistan (542 occurrences).
ASAS = All-Sky Automated Survey project (478 occurrences).
Kelt-E = Kilodegree Extremely Little Telescope East (1535 occurrences).
Kelt-W = Kilodegree Extremely Little Telescope West (1354 occurrences).
ASAS-SN = All-Sky Automated Survey for SuperNovae (799 occurrences).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Jul-2018