J/ApJ/922/5 Optical to NIR light curves of WR 122 (Lau+, 2021)
Discovery of a 310 day period from the enshrouded massive system NaSt1 (WR 122).
Lau R.M., Tinyanont S., Hankins M.J., Ashley M.C.B., De K.,
Filippenko A.V., Hillenbrand L.A., Kasliwal M.M., Mauerhan J.C.,
Moffat A.F.J., Moore A.M., Smith N., Soon J., Soria R., Travouillon T.,
van der Hucht K.A., Williams P.M., Zheng W.
<Astrophys. J., 922, 5 (2021)>
=2021ApJ...922....5L 2021ApJ...922....5L
ADC_Keywords: Stars, Wolf-Rayet; Photometry, UBVRI; Photometry, infrared
Keywords: Massive stars ; Interacting binary stars ; Wolf-Rayet stars ;
Light curves ; Circumstellar dust
Abstract:
We present optical and infrared (IR) light curves of NaSt1, also known
as Wolf-Rayet 122, with observations from Palomar Gattini-IR (PGIR),
the Zwicky Transient Facility (ZTF), the Katzman Automatic Imaging
Telescope, the Asteroid Terrestrial-impact Last Alert System, and the
All-Sky Automated Survey for Supernovae (ASAS-SN). We identify a
P=309.7±0.7day photometric period from the optical and IR light
curves that reveal periodic, sinusoidal variability between 2014 July
and 2021 July. We also present historical IR light curves taken
between 1983 July and 1989 May, which show variability consistent with
the period of the present-day light curves. In the past, NaSt1 was
brighter in the J band with larger variability amplitudes than the
present-day PGIR values, suggesting that NaSt1 exhibits variability on
longer (≳decade) timescales. Sinusoidal fits to the recent optical
and IR light curves show that the amplitude of NaSt1's variability
differs at various wavelengths and also reveal significant phase
offsets of 17.0±2.5day between the ZTF r and PGIR J light curves. We
interpret the 310 day photometric period from NaSt1 as the orbital
period of an enshrouded massive binary. We suggest that the
photometric variability of NaSt1 may arise from variations in the
line-of-sight optical depth toward circumstellar optical/IR-emitting
regions throughout its orbit due to colliding-wind dust formation. We
speculate that past mass transfer in NaSt1 may have been triggered by
Roche-lobe overflow (RLOF) during an eruptive phase of an Ofpe/WN9
star. Lastly, we argue that NaSt1 is no longer undergoing RLOF mass
transfer.
Description:
The Palomar Gattini-IR (PGIR) is a wide-field, time-domain imaging
survey located at Palomar Observatory. It utilizes a 30cm telescope
and J-band filter similar to the 2MASS J filter (λeff=1.235um
and Δλ=0.1624um). In order to investigate the J-band
variability of NaSt1, forced-aperture photometry was performed at its
coordinates using a 3 resampled-pixel radius (∼13") aperture in PGIR
images taken between 2018 November and 2021 June. See Section 2.1.
Optical BVRI photometry of NaSt1 was obtained with the robotic 0.76m
Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory.
Additional Clear-band (close to the R band) images were also obtained
with KAIT. A series of 66 imaging observations of NaSt1 was performed
with KAIT between 2014 July and 2015 November. See Section 2.2.
Mid-IR observations of NaSt1 were made using The Broadband Array
Spectrograph System (BASS) sensor at the 3.6m Advanced Electro-Optical
System (AEOS) telescope on Haleakela, HI, on 2017 October 23, 2018 May
13, 2019 April 6, and 2019 August 24 (UT). See Section 2.3.
We also utilize the g-band and r-band PSF-fit photometry of NaSt1 from
the Zwicky Transient Facility (ZTF) Public Data Release 6. 18 ZTF
observations of NaSt1 were taken between 2018 April and 2021 April
with a ∼1 day cadence when visible. The V-band photometry from the
All-Sky Automated Survey for Supernovae (ASAS-SN). Photometry of NaSt1
was obtained from the ASAS-SN Variable Star Database and the
photometric measurements obtained by the Asteroid Terrestrial-impact
Last Alert System (ATLAS) project between 2015 October 23 (MJD 57318)
and 2021 July 9 (MJD 59404) from the ATLAS forced-photometry server in
orange ("o-band"; λeff=6632Å) and cyan ("c-band";
λeff= 5184Å) filters. See Section 2.5.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
----------------------------------------------------------
18 52 17.54 +00 59 44.3 NaSt1 = WR 122 (P=309.7)
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 154 1082 KAIT, ATLAS, ASAS-SN, ZTF, and PGIR photometry
of NaSt1
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See also:
II/183 : UBVRI Photometric Standards (Landolt 1992)
J/A+AS/119/547 : IR photometry of ESO calibration stars (van der Bliek+ 1996)
J/AJ/129/2018 : RXTE scaled fluxes of eta Car (Corcoran+, 2005)
J/A+A/504/959 : Amplitudes of single-mode Cepheids (Klagyivik+, 2009)
J/ApJS/190/418 : Light curves for 165 SNe (Ganeshalingam+, 2010)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/MNRAS/465/2432 : MiMeS magnetic analysis of O-type stars (Grunhut+, 2017)
J/A+A/615/A78 : Spectral models for binary products (Goetberg+, 2018)
J/AJ/156/241 : Catalog of variable stars measured by ATLAS (Heinze+, 2018)
J/A+A/627/A175 : GLOSTAR. Radio Source Catalogue I (Medina+ 2019)
J/MNRAS/488/1282 : Variable dust emission by WC type WR* (Williams, 2019)
J/ApJ/901/L7 : NIR obs. of the Gal. magnetar SGR1935+215 (De+, 2020)
J/ApJ/893/11 : Massive star variability in M31 from iPTF (Soraisam+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d MJD [56818.4/59404.4] Modified Julian Date
12- 17 F6.3 mag BmagK [16.13/16.3]? Apparent KAIT B band Vega magnitude
19- 23 F5.3 mag e_BmagK [0.036/0.2]? Uncertainty in BmagK
25- 30 F6.3 mag gmagZ [15.25/15.5]? Apparent ZTF g band Vega magnitude
32- 36 F5.3 mag e_gmagZ [0.03/0.04]? Uncertainty in gmagZ
38- 43 F6.3 mag cmagA [14.27/14.5]? Apparent ATLAS 'cyan' band Vega
magnitude
45- 49 F5.3 mag e_cmagA [0.004/0.03]? Uncertainty in cmagA
51- 56 F6.3 mag VmagK [13.94/14.11]? Apparent KAIT V band Vega
magnitude
58- 64 F7.5 mag e_VmagK [0.023/0.025]? Uncertainty in VmagK
66- 71 F6.3 mag VmagA [14.3/14.51]? Apparent ASAS-SN V band Vega
magnitude
73- 77 F5.3 mag e_VmagA [0.016/0.03]? Uncertainty in VmagA
79- 84 F6.3 mag rmagZ [12.7/13]? Apparent ZTF r band Vega magnitude
86- 90 F5.3 mag e_rmagZ [0.02/0.03]? Uncertainty in rmagZ
92- 97 F6.3 mag RmagK [12.6/13]? Apparent KAIT R band Vega magnitude
99- 103 F5.3 mag e_RmagK [0.015]? Uncertainty in RmagK
105- 110 F6.3 mag omagA [12.44/12.8]? Apparent 'orange' band Vega
magnitude
112- 116 F5.3 mag e_omagA [0.002/0.06]? Uncertainty in omagA
118- 123 F6.3 mag ClmagK [12.83/13.1]? Apparent KAIT clear band Vega
magnitude
125- 129 F5.3 mag e_ClmagK [0.004/0.03]? Uncertainty in ClmagK
131- 136 F6.3 mag ImagK [12.23/12.4]? Apparent KAIT I band Vega magnitude
138- 142 F5.3 mag e_ImagK [0.03/0.04]? Uncertainty in ImagK
144- 148 F5.3 mag JmagP [9.43/9.8]? Apparent PGIR J band Vega magnitude
150- 154 F5.3 mag e_JmagP [0.007/0.03]? Uncertainty in JmagP
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Mar-2023