Gaia21bty: an EXor light curve exhibiting a FUor spectrum

Michal Siwak; Lynne A.  Hillenbrand; Ágnes Kóspál; Péter Ábrahám; Teresa Giannini; Kishalay  De; Attila  Moór; Máté Szilágyi; Jan  Janík; Chris Koen; Sunkyung Park; Zsófia Nagy; Fernando Cruz-Sáenz de Miera; Eleonora Fiorellino; Gábor Marton; Mária Kun; Philip W. Lucas; Andrej Udalski; Zsofia Marianna Szabo

doi:10.1093/mnras/stad2135

Gaia21bty: an EXor light curve exhibiting a FUor spectrum

Michal Siwak^*, Lynne A. Hillenbrand, Ágnes Kóspál, Péter Ábrahám, Teresa Giannini, Kishalay De, Attila Moór, Máté Szilágyi, Jan Janík, Chris Koen, Sunkyung Park, Zsófia Nagy, Fernando Cruz-Sáenz de Miera, Eleonora Fiorellino, Gábor Marton, Mária Kun, Philip W. Lucas, Andrej Udalski, Zsofia Marianna Szabo

^*Corresponding author for this work

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

Gaia21bty, a pre-main-sequence star that previously had shown aperiodic dips in its light curve, underwent a considerable ΔG ≈ 2.9 mag brightening that occurred over a few months between 2020 October and 2021 February. The Gaia light curve shows that the star remained near maximum brightness for about 4–6 months, and then started slowly fading over the next 2 yr, with at least three superimposed ∼1 mag sudden rebrightening events. Whereas the amplitude and duration of the maximum is typical for EX Lupi-type stars, optical and near-infrared spectra obtained at the maximum are dominated by features which are typical for FU Ori-type stars (FUors). Modelling of the accretion disc at the maximum indicates that the disc bolometric luminosity is 43 L⊙ and the mass accretion rate is 2.5 × 10−5 M⊙ yr−1, which are typical values for FUors even considering the large uncertainty in the distance (⁠1.7+0.8−0.4 kpc). Further monitoring is necessary to understand the cause of the quick brightness decline, the rebrightening, and the other post-outburst light changes, as our multicolour photometric data suggest that they could be caused by a long and discontinuous obscuration event. We speculate that the outburst might have induced large-scale inhomogeneous dust condensations in the line of sight leading to such phenomena, whilst the FUor outburst continues behind the opaque screen.

Original language	English
Pages (from-to)	5548–5565
Number of pages	18
Journal	Monthly Notices of the Royal Astronomical Society
Volume	524
Issue number	4
Early online date	18 Jul 2023
DOIs	https://doi.org/10.1093/mnras/stad2135
Publication status	Published - Oct 2023

Keywords

Accretion
Accretion discs
Stars: formation
Stars: pre-main-sequence
Stars: variables: T Tauri, Herbig Ae/Be

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10.1093/mnras/stad2135

Siwak-2023-Gaia21bty-stad2135-524-4-5548
Copyright © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/stad2135.
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https://arxiv.org/abs/2307.08802Licence: CC BY

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Siwak, M., Hillenbrand, L. A., Kóspál, Á., Ábrahám, P., Giannini, T., De, K., Moór, A., Szilágyi, M., Janík, J., Koen, C., Park, S., Nagy, Z., Cruz-Sáenz de Miera, F., Fiorellino, E., Marton, G., Kun, M., Lucas, P. W., Udalski, A., & Szabo, Z. M. (2023). Gaia21bty: an EXor light curve exhibiting a FUor spectrum. Monthly Notices of the Royal Astronomical Society, 524(4), 5548–5565. https://doi.org/10.1093/mnras/stad2135

@article{12eea8a784024b46b6a74a66cf363816,

title = "Gaia21bty: an EXor light curve exhibiting a FUor spectrum",

abstract = "Gaia21bty, a pre-main-sequence star that previously had shown aperiodic dips in its light curve, underwent a considerable ΔG ≈ 2.9 mag brightening that occurred over a few months between 2020 October and 2021 February. The Gaia light curve shows that the star remained near maximum brightness for about 4–6 months, and then started slowly fading over the next 2 yr, with at least three superimposed ∼1 mag sudden rebrightening events. Whereas the amplitude and duration of the maximum is typical for EX Lupi-type stars, optical and near-infrared spectra obtained at the maximum are dominated by features which are typical for FU Ori-type stars (FUors). Modelling of the accretion disc at the maximum indicates that the disc bolometric luminosity is 43 L⊙ and the mass accretion rate is 2.5 × 10−5 M⊙ yr−1, which are typical values for FUors even considering the large uncertainty in the distance (⁠1.7+0.8−0.4 kpc). Further monitoring is necessary to understand the cause of the quick brightness decline, the rebrightening, and the other post-outburst light changes, as our multicolour photometric data suggest that they could be caused by a long and discontinuous obscuration event. We speculate that the outburst might have induced large-scale inhomogeneous dust condensations in the line of sight leading to such phenomena, whilst the FUor outburst continues behind the opaque screen.",

keywords = "Accretion, Accretion discs, Stars: formation, Stars: pre-main-sequence, Stars: variables: T Tauri, Herbig Ae/Be",

author = "Michal Siwak and Hillenbrand, {Lynne A.} and {\'A}gnes K{\'o}sp{\'a}l and P{\'e}ter {\'A}brah{\'a}m and Teresa Giannini and Kishalay De and Attila Mo{\'o}r and M{\'a}t{\'e} Szil{\'a}gyi and Jan Jan{\'i}k and Chris Koen and Sunkyung Park and Zs{\'o}fia Nagy and {Cruz-S{\'a}enz de Miera}, Fernando and Eleonora Fiorellino and G{\'a}bor Marton and M{\'a}ria Kun and Lucas, {Philip W.} and Andrej Udalski and Szabo, {Zsofia Marianna}",

note = "Funding: This project has received funding from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 research and innovation programme under grant agreement No. 716155 (SACCRED). We acknowledge support from the ESA PRODEX Contract No. 4000132054. GM and ZN were supported by the J{\'a}nos Bolyai Research Scholarship of the Hungarian Academy of Sciences. GM acknowledges support from the European Union{\textquoteright}s Horizon 2020 research and innovation programme under grant agreement No. 101004141. EF acknowledges financial support from the project PRIN-INAF 2019 {\textquoteleft}Spectroscopically Tracing the Disc Dispersal Evolution (STRADE){\textquoteright}. ZMS acknowledges funding from a St Leonards scholarship from the University of St Andrews.",

year = "2023",

month = oct,

doi = "10.1093/mnras/stad2135",

language = "English",

volume = "524",

pages = "5548–5565",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "4",

}

Siwak, M, Hillenbrand, LA, Kóspál, Á, Ábrahám, P, Giannini, T, De, K, Moór, A, Szilágyi, M, Janík, J, Koen, C, Park, S, Nagy, Z, Cruz-Sáenz de Miera, F, Fiorellino, E, Marton, G, Kun, M, Lucas, PW, Udalski, A & Szabo, ZM 2023, 'Gaia21bty: an EXor light curve exhibiting a FUor spectrum', Monthly Notices of the Royal Astronomical Society, vol. 524, no. 4, pp. 5548–5565. https://doi.org/10.1093/mnras/stad2135

TY - JOUR

T1 - Gaia21bty

T2 - an EXor light curve exhibiting a FUor spectrum

AU - Siwak, Michal

AU - Hillenbrand, Lynne A.

AU - Kóspál, Ágnes

AU - Ábrahám, Péter

AU - Giannini, Teresa

AU - De, Kishalay

AU - Moór, Attila

AU - Szilágyi, Máté

AU - Janík, Jan

AU - Koen, Chris

AU - Park, Sunkyung

AU - Nagy, Zsófia

AU - Cruz-Sáenz de Miera, Fernando

AU - Fiorellino, Eleonora

AU - Marton, Gábor

AU - Kun, Mária

AU - Lucas, Philip W.

AU - Udalski, Andrej

AU - Szabo, Zsofia Marianna

N1 - Funding: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 716155 (SACCRED). We acknowledge support from the ESA PRODEX Contract No. 4000132054. GM and ZN were supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences. GM acknowledges support from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004141. EF acknowledges financial support from the project PRIN-INAF 2019 ‘Spectroscopically Tracing the Disc Dispersal Evolution (STRADE)’. ZMS acknowledges funding from a St Leonards scholarship from the University of St Andrews.

PY - 2023/10

Y1 - 2023/10

N2 - Gaia21bty, a pre-main-sequence star that previously had shown aperiodic dips in its light curve, underwent a considerable ΔG ≈ 2.9 mag brightening that occurred over a few months between 2020 October and 2021 February. The Gaia light curve shows that the star remained near maximum brightness for about 4–6 months, and then started slowly fading over the next 2 yr, with at least three superimposed ∼1 mag sudden rebrightening events. Whereas the amplitude and duration of the maximum is typical for EX Lupi-type stars, optical and near-infrared spectra obtained at the maximum are dominated by features which are typical for FU Ori-type stars (FUors). Modelling of the accretion disc at the maximum indicates that the disc bolometric luminosity is 43 L⊙ and the mass accretion rate is 2.5 × 10−5 M⊙ yr−1, which are typical values for FUors even considering the large uncertainty in the distance (⁠1.7+0.8−0.4 kpc). Further monitoring is necessary to understand the cause of the quick brightness decline, the rebrightening, and the other post-outburst light changes, as our multicolour photometric data suggest that they could be caused by a long and discontinuous obscuration event. We speculate that the outburst might have induced large-scale inhomogeneous dust condensations in the line of sight leading to such phenomena, whilst the FUor outburst continues behind the opaque screen.

AB - Gaia21bty, a pre-main-sequence star that previously had shown aperiodic dips in its light curve, underwent a considerable ΔG ≈ 2.9 mag brightening that occurred over a few months between 2020 October and 2021 February. The Gaia light curve shows that the star remained near maximum brightness for about 4–6 months, and then started slowly fading over the next 2 yr, with at least three superimposed ∼1 mag sudden rebrightening events. Whereas the amplitude and duration of the maximum is typical for EX Lupi-type stars, optical and near-infrared spectra obtained at the maximum are dominated by features which are typical for FU Ori-type stars (FUors). Modelling of the accretion disc at the maximum indicates that the disc bolometric luminosity is 43 L⊙ and the mass accretion rate is 2.5 × 10−5 M⊙ yr−1, which are typical values for FUors even considering the large uncertainty in the distance (⁠1.7+0.8−0.4 kpc). Further monitoring is necessary to understand the cause of the quick brightness decline, the rebrightening, and the other post-outburst light changes, as our multicolour photometric data suggest that they could be caused by a long and discontinuous obscuration event. We speculate that the outburst might have induced large-scale inhomogeneous dust condensations in the line of sight leading to such phenomena, whilst the FUor outburst continues behind the opaque screen.

KW - Accretion

KW - Accretion discs

KW - Stars: formation

KW - Stars: pre-main-sequence

KW - Stars: variables: T Tauri, Herbig Ae/Be

U2 - 10.1093/mnras/stad2135

DO - 10.1093/mnras/stad2135

M3 - Article

SN - 0035-8711

VL - 524

SP - 5548

EP - 5565

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 4

ER -

Gaia21bty: an EXor light curve exhibiting a FUor spectrum

Abstract

Keywords

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