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Discovery of a 300-day Period from the Enshrouded Massive Binary NaSt1 (WR 122), a Product of Binary Interaction

Lau, Ryan M. and Tinyanont, Samaporn and Hankins, Matthew J. and Ashley, Michael C. B. and De, Kishalay and Filippenko, Alexei V. and Hillenbrand, Lynne A. and Kasliwal, Mansi M. and Mauerhan, Jon C. and Moffat, Anthony F. J. and Moore, Anna M. and Smith, Nathan and Soon, Jamie and Soria, Roberto and Travouillon, Tony and van der Hucht, Karel A. and Williams, Peredur M. and Zheng, WeiKang (2021) Discovery of a 300-day Period from the Enshrouded Massive Binary NaSt1 (WR 122), a Product of Binary Interaction. . (Submitted)

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We present optical and infrared (IR) light curves of the enshrouded massive binary NaSt1 (WR 122) with observations from Palomar Gattini-IR (PGIR), the Zwicky Transient Facility (ZTF), the Katzman Automatic Imaging Telescope (KAIT), and the All-Sky Automated Survey for Supernovae (ASAS-SN). The optical and IR light curves span between 2014 July and 2020 Oct., revealing periodic, sinusoidal variability from NaSt1 with a P=305.2±1.0 d period. We also present historical IR light curves taken between 1983 July and 1989 May that also indicate NaSt1 exhibits long-term IR variability on timescales of ∼decades. Fixed-period sinusoidal fits to the recent optical and IR light curves show that amplitude of NaSt1's variability is different at different wavelengths and also reveal significant phase offsets of ∼18 d between the ZTF r and PGIR J light curves.We interpret the ∼300 d period of the observed variability as the orbital period of a binary system in NaSt1. Assuming a circular orbit and adopting a range of combined stellar mass values in the range 20-100 M⊙ in NaSt1, we estimate orbital separations of ∼2-4 au. We suggest that the sinusoidal 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 provide an interpretation on the nature of NaSt1 and speculate that the mass-transfer process may have been triggered by Roche-lobe overflow (RLOF) during an eruptive phase of a Ofpe/WN9 star. Lastly, we claim that NaSt1 ceased RLOF mass transfer ≲3400 yr ago.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Tinyanont, Samaporn0000-0002-1481-4676
Hankins, Matthew J.0000-0001-9315-8437
Ashley, Michael C. B.0000-0003-1412-2028
De, Kishalay0000-0002-8989-0542
Filippenko, Alexei V.0000-0003-3460-0103
Kasliwal, Mansi M.0000-0002-5619-4938
Mauerhan, Jon C.0000-0002-7555-8741
Moffat, Anthony F. J.0000-0002-4333-9755
Moore, Anna M.0000-0002-2894-6936
Smith, Nathan0000-0001-5510-2424
Soria, Roberto0000-0002-4622-796X
Travouillon, Tony0000-0001-9304-6718
Williams, Peredur M.0000-0002-8092-980X
Zheng, WeiKang0000-0002-2636-6508
Additional Information:We thank T. Jayasinghe for discussion of the technical details of the filter properties in the ASAS-SN survey. R.M.L. acknowledges the Japan Aerospace Exploration Agency's International Top Young Fellowship (ITYF). A.F.J.M. is grateful for financial assistance from NSERC (Canada). M.M.K. acknowledges the Heising-Simons foundation for support via a Scialog fellowship of the Research Corporation. M.M.K. and A.M.M. acknowledge the Mt. Cuba Astronomical Foundation. A.V.F. is grateful for financial assistance from the TABASGO Foundation, the Christopher R. Redlich Fund, and the U.C. Berkeley Miller Institute for Basic Research in Science (where he is a Miller Senior Fellow). M.M.K. acknowledges generous support from the David and Lucille Packard Foundation. J.S. is supported by an Australian Government Research Training Program (RTP) Scholarship. Palomar Gattini-IR (PGIR) is generously funded by Caltech, Australian National University, the Mt. Cuba Astronomical Foundation, the Heising-Simons Foundation, and the Binational Science Foundation. PGIR is a collaborative project among Caltech, Australian National University, University of New South Wales, Columbia University, and the Weizmann Institute of Science. Based in part on observations obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation (NSF) under grant AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by Caltech Optical Observatories, IPAC, and the University of Washington. We thank the Las Cumbres Observatory and its staff for its continuing support of the ASAS-SN project. LCOGT observations were performed as part of DDT award 2019B003 to E.G. ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, and NSF grants AST-1515927 and AST-1908570. Development of ASAS-SN has been supported by NSF grant AST-0908816, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CAS-SACA), the Villum Foundation, and George Skestos. UKIRT is owned by the University of Hawaii (UH) and operated by the UH Institute for Astronomy; operations are enabled through the cooperation of the East Asian Observatory. When the data reported here were acquired, UKIRT was operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the U.K. Research at Lick Observatory is partially supported by a generous gift from Google. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, Auto-Scope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. This research made use of Astropy,7 a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018). Facilities: PGIR, KAIT, ZTF, ASAS-SN, AEOS (BASS), UKIRT, ESO 1-m.
Group:Astronomy Department, Zwicky Transient Facility
Funding AgencyGrant Number
Japan Aerospace Exploration Agency (JAXA)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Research CorporationUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Christopher R. Redlich FundUNSPECIFIED
Miller Institute for Basic Research in ScienceUNSPECIFIED
David and Lucille Packard FoundationUNSPECIFIED
Australian GovernmentUNSPECIFIED
Australian National UniversityUNSPECIFIED
Binational Science Foundation (USA-Israel)UNSPECIFIED
ZTF partner institutionsUNSPECIFIED
Gordon and Betty Moore FoundationGBMF5490
Center for Cosmology and AstroParticle Physics (CCAPP)UNSPECIFIED
Chinese Academy of Sciences South America Center for Astronomy (CASSACA)UNSPECIFIED
Villum FoundationUNSPECIFIED
Sun MicrosystemsUNSPECIFIED
Hewlett-Packard CompanyUNSPECIFIED
Auto-Scope CorporationUNSPECIFIED
Lick ObservatoryUNSPECIFIED
University of CaliforniaUNSPECIFIED
Sylvia and Jim Katzman FoundationUNSPECIFIED
Subject Keywords:massive stars; interacting binary stars; Wolf-Rayet stars; light curves; circumstellar dust
Record Number:CaltechAUTHORS:20210318-154128565
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108495
Deposited By: Tony Diaz
Deposited On:19 Mar 2021 00:02
Last Modified:19 Mar 2021 00:02

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