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Revealing Efficient Dust Formation at Low Metallicity in Extragalactic Carbon-rich Wolf-Rayet Binaries

Lau, Ryan M. and Hankins, Matthew J. and Kasliwal, Mansi M. and Bond, Howard E. and De, Kishalay and Jencson, Jacob E. and Moffat, Anthony F. J. and Smith, Nathan and Williams, Peredur M. (2021) Revealing Efficient Dust Formation at Low Metallicity in Extragalactic Carbon-rich Wolf-Rayet Binaries. Astrophysical Journal, 909 (2). Art. No. 113. ISSN 1538-4357. doi:10.3847/1538-4357/abd8cd.

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We present Spitzer/InfraRed Array Camera observations of dust formation from six extragalactic carbon-rich Wolf-Rayet (WC) binary candidates in low-metallicity (Z ≲ 0.65 Z_⊙) environments using multiepoch mid-infrared (IR) imaging data from the SPitzer InfraRed Intensive Transients Survey (SPIRITS). Optical follow-up spectroscopy of SPIRITS 16ln, 19q, 16df, 18hb, and 14apu reveals emission features from C IV λ5801−12 and/or the C III–IV λ4650/He II λ4686 blend that are consistent with early-type WC stars. We identify SPIRITS 16ln as the variable mid-IR counterpart of the recently discovered colliding-wind WC4 + O binary candidate, N604-WRXc, located in the subsolar metallicity NGC 604 H II region in M33. We interpret the mid-IR variability from SPIRITS 16ln as a dust-formation episode in an eccentric colliding-wind WC binary. SPIRITS 19q, 16df, 14apu, and 18hb exhibit absolute [3.6] magnitudes exceeding that of one of the most IR-luminous dust-forming WC systems known, WR 104 (M_([3.6]) ≲ −12.3). An analysis of dust formation in the mid-IR outburst from SPIRITS 19q reveals a high dust production rate of Ṁ_d ≳ 2 × 10⁻⁶ M_⊙ yr⁻¹, which may therefore exceed that of the most efficient dust-forming WC systems known. We demonstrate that efficient dust formation is feasible from early-type WC binaries in the theoretical framework of colliding-wind binary dust formation if the systems host an O-type companion with high mass-loss rates (Ṁ ≳ 1.6 × 10⁻⁶ M_⊙ yr⁻¹). This efficient dust formation from early-type WC binaries highlights their potential role as significant sources of dust in low-metallicity environments.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hankins, Matthew J.0000-0001-9315-8437
Kasliwal, Mansi M.0000-0002-5619-4938
Bond, Howard E.0000-0003-1377-7145
De, Kishalay0000-0002-8989-0542
Jencson, Jacob E.0000-0001-5754-4007
Moffat, Anthony F. J.0000-0002-4333-9755
Smith, Nathan0000-0001-5510-2424
Williams, Peredur M.0000-0002-8092-980X
Additional Information:© 2021. The American Astronomical Society. Received 2020 November 13; revised 2021 January 4; accepted 2021 January 4; published 2021 March 10. We acknowledge S. Anand and C. Fremling for their support on the observations obtained with Keck I/LRIS. We thank N. Morrell, P. Mudumba, and R. Gehrz for their valuable feedback on our study. We also thank the anonymous referee for their insightful review and comments that have improved the quality of our work. 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). This work is based on observations and archival data obtained with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The Hobby–Eberly Telescope (HET) is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. The Low Resolution Spectrograph 2 (LRS2) was developed and funded by the University of Texas at Austin McDonald Observatory and Department of Astronomy and by Pennsylvania State University. We thank the Leibniz-Institut für Astrophysik Potsdam (AIP) and the Institut für Astrophysik Göttingen (IAG) for their contributions to the construction of the integral field units. Based partially on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Facilities: Spitzer(IRAC) - Spitzer Space Telescope satellite, Keck:I (LRIS) - , Keck:II (NIRES) - , HET(LRS2) - , P200(WIRC) - , HST(ACS/WFC) - Software: Astropy (Astropy Collaboration et al. 2013, 2018), LPipe (Perley 2019), Spex-tool (Cushing et al. 2004), Panacea (
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Aerospace Exploration Agency (JAXA)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
McDonald ObservatoryUNSPECIFIED
Pennsylvania State UniversityUNSPECIFIED
NASANAS 5-26555
Subject Keywords:Wolf-Rayet stars; WC stars; Circumstellar dust; Time domain astronomy; Infrared astronomy; Stellar winds
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Wolf-Rayet stars (1806); WC stars (1793); Circumstellar dust (236); Time domain astronomy (2109); Infrared astronomy (786); Stellar winds (1636)
Record Number:CaltechAUTHORS:20210204-092725706
Persistent URL:
Official Citation:Ryan M. Lau et al 2021 ApJ 909 113
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107909
Deposited By: George Porter
Deposited On:05 Feb 2021 20:53
Last Modified:16 Nov 2021 19:07

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