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Evidence for Centrifugal Breakout around the Young M Dwarf TIC 234284556

Palumbo, Elsa K. and Montet, Benjamin T. and Feinstein, Adina D. and Bouma, Luke G. and Hartman, Joel D. and Hillenbrand, Lynne A. and Gully-Santiago, Michael A. and Banks, Kirsten A. (2022) Evidence for Centrifugal Breakout around the Young M Dwarf TIC 234284556. Astrophysical Journal, 925 (1). Art. No. 75. ISSN 0004-637X. doi:10.3847/1538-4357/ac38a5.

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Magnetospheric clouds have been proposed as explanations for depth-varying dips in the phased light curves of young, magnetically active stars such as σ Ori E and RIK-210. However, the stellar theory that first predicted magnetospheric clouds also anticipated an associated mass-balancing mechanism known as centrifugal breakout for which there has been limited empirical evidence. In this paper, we present data from the Transiting Exoplanet Survey Satellite, Las Cumbres Observatory, All-Sky Automated Survey for Supernovae, and Veloce on the 45 Myr M3.5 star TIC 234284556, and propose that it is a candidate for the direct detection of centrifugal breakout. In assessing this hypothesis, we examine the sudden (∼1 day timescale) disappearance of a previously stable (∼1 month timescale) transit-like event. We also interpret the presence of an anomalous brightening event that precedes the disappearance of the signal, analyze rotational amplitudes and optical flaring as a proxy for magnetic activity, and estimate the mass of gas and dust present immediately prior to the potential breakout event. After demonstrating that our spectral and photometric data support a magnetospheric cloud and centrifugal breakout model and disfavor alternate scenarios, we discuss the possibility of a coronal mass ejection or stellar wind origin of the corotating material and we introduce a reionization mechanism as a potential explanation for more gradual variations in eclipse parameters. Finally, after comparing TIC 234284556 with previously identified “flux-dip” stars, we argue that TIC 234284556 may be an archetypal representative of a whole class of young, magnetically active stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Palumbo, Elsa K.0000-0001-7967-1795
Montet, Benjamin T.0000-0001-7516-8308
Feinstein, Adina D.0000-0002-9464-8101
Bouma, Luke G.0000-0002-0514-5538
Hartman, Joel D.0000-0001-8732-6166
Gully-Santiago, Michael A.0000-0002-4020-3457
Banks, Kirsten A.0000-0001-5210-1696
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 July 2; revised 2021 November 9; accepted 2021 November 9; published 2022 January 26. We thank Richard Townsend, Katja Poppenhaeger, Trevor David, Christina Hedges, and an anonymous referee for thought-provoking conversations and insights into the TIC 234284556 system which improved the quality of this manuscript. We thank Chris Tinney for helpful discussions on Veloce observing modes. E.K.P. thanks Nils Palumbo (University of Wisconsin-Madison) for much-appreciated coding advice, the NEarby Worlds and Their Stars (NEWTS) group (PI: B. Montet, UNSW) for welcoming her into their lab, and the Caltech Beans for moral support throughout the research process. This paper relies on data from the TESS mission, which is funded by the NASA Explorer Program. TESS data were obtained from the Mikulski Archive for Space Telescopes (MAST), which is supported in part by the NASA Office of Space Science's grant NNX13AC07G. This research made use of the SIMBAD database, operated at CDS, Strasbourg, France and of the Exoplanet Follow-up Observation Program (ExoFOP) website, which is operated by the Caltech, under contract with NASA via the Exoplanet Exploration Program. This work used data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work makes use of observations from the Las Cumbres Observatory global telescope network, in particular the Sinistro camera on the LCO-1m telescope at the South African Astronomical Observatory. The LCO observations were conducted under the auspices of NOIRLab program NOAO2020B-013 (PI: J. Hartman). This research also made use of ASAS-SN data. ASAS-SN is funded by the Gordon and Betty Moore Foundation under the 5 year grant GBMF5490 as well as by the National Science Foundation under grants AST-151592 and AST-1908570, with telescopes hosted by LCO. This work was also based in part on data obtained at the Anglo-Australian Telescope under program A/2020B/09. We acknowledge the traditional owners of the land on which the AAT stands, the Gamilaraay people, and pay our respects to elders past and present. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1746045. E.K.P.'s role in this research was funded by Caltech's Summer Undergraduate Research Fellowship (SURF) program, with generous support from Carl F. Braun and Harold and Mary Zirin. L.G.B. and J.H. acknowledge support by the TESS GI Program, programs G011103 and G022117, through NASA grants 80NSSC19K0386 and 80NSSC19K1728. J.H. acknowledges additional support from NASA grant NNX17AB61G. Facilities: TESS, ASAS-SN - , LCO (SAAO) - , Siding Spring Observatory (Veloce) - , MAST - , Simbad. - Software: astropy (Price-Whelan et al. 2018), CurveFit (Caltech 2021) eleanor (Feinstein et al. 2019), emcee (Foreman-Mackey et al. 2013), exoplanet (Foreman-Mackey et al. 2020), itertools (Van Rossum 2020), lightkurve (Lightkurve Collaboration et al. 2018), Mathematica (Wolfram Research 2020), matplotlib (Hunter 2007), numpy (Van Der Walt et al. 2011), os, pickle (Van Rossum 2020), pymc3 (Salvatier et al. 2016), scipy (Virtanen et al. 2020), statsmodels (Seabold & Perktold 2010), stella (Feinstein et al. 2020a), theano (The Theano Development Team et al. 2016), transitleastsquares (Hippke & Heller 2019), uncertainties (Lebigot 2010).
Group:Astronomy Department
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
Gordon and Betty Moore FoundationGBMF5490
NSF Graduate Research FellowshipDGE-1746045
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Harold and Mary ZirinUNSPECIFIED
Subject Keywords:M dwarf stars; Stellar coronal mass ejections; Stellar magnetic fields; Stellar flares; Stellar winds
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: M dwarf stars (982); Stellar coronal mass ejections (1881); Stellar magnetic fields (1610); Stellar flares (1603); Stellar winds (1636)
Record Number:CaltechAUTHORS:20220203-316653000
Persistent URL:
Official Citation:Elsa K. Palumbo et al 2022 ApJ 925 75
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113247
Deposited By: George Porter
Deposited On:04 Feb 2022 18:59
Last Modified:04 Feb 2022 18:59

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