The Many-faceted Light Curves of Young Disk-bearing Stars in Taurus as Seen by K2

Cody, Ann Marie; Hillenbrand, Lynne A.; Rebull, L. M.

doi:10.3847/1538-3881/ac5b73

Cited by 22 publications

(26 citation statements)

References 73 publications

(97 reference statements)

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“…We have classified 323 stars using the Q − M variability plane, to quantify flux asymmetry and waveform repeatability in the light curves. This ratio is similar to that in Taurus with 70% and 30%, respectively (Cody et al 2022). 5.…”

Section: Discussionsupporting

confidence: 84%

“…There is some expectation that the light-curve morphological classes could correlate with infrared excess. Using K2 data sets, several previous studies, namely Cody & Hillenbrand (2018) in Oph/Sco, Cody et al (2022) in Taurus, and Venuti et al (2021) in the Lagoon Nebula all found that both the periodic (P) and the QPS sources tend to have lower values of infrared excess on average, and in fact dominate the source population at small infrared color values. This is consistent with a relatively clean line of sight to the spotted stellar photosphere, and a lack of accretion effects in the light curve.…”

Section: Correlation Of Variability Properties With Infrared Excessmentioning

confidence: 99%

“…Figure 11 shows one infrared color as a function of our normalized variability amplitude metric. Relative to the variability morphology versus infrared color analysis in Cody & Hillenbrand (2018) studying Upper Sco and Cody et al (2022) studying Taurus, we may be more subject here in the NAP region to the effects of reddening. Thus, to de-redden the color-color diagrams, we adopted the A V values of in Fang et al (2020) and the near-and mid-infrared extinction results of Xue et al (2016).…”

Section: Correlation Of Variability Properties With Infrared Excessmentioning

confidence: 99%

“…To do so, we refer to Table 3 in Cody et al (2022), which includes the Taurus, Oph, and NGC 2264 regions studied with K2 and CoRoT data taken from space-based platforms. We focus our comparisons on the young regions with comparable ages to the NAP.…”

Section: Comparison To Q − M Distributions In Other Star-forming Regionsmentioning

confidence: 99%

“…We assess in this appendix the transferability of these metrics from space-based to ground-based data. To do so, we explore how Q behaves on a K2 data set-specifically the ∼100 young stars in the Taurus region with light curves reported in Cody et al (2022), and versions of these data that have been degraded to the cadence and precision typical of our ground-based ZTF data set.…”

Section: Appendix B a Lesson Regarding True Periods Near The Observin...mentioning

confidence: 99%

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A Zwicky Transient Facility Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

Hillenbrand¹,

Kiker²,

Gee³

et al. 2022

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We present a study of 323 photometrically variable young stellar objects that are likely members of the North America and Pelican nebulae star-forming region. To do so, we utilize over two years of data in the g and r photometric bands from the Zwicky Transient Facility. We first investigate periodic variability, finding 46 objects (∼15% of the sample) with significant periods that phase well and can be attributed to stellar rotation. We then use the quasiperiodicity (Q) and flux asymmetry (M) variability metrics to assign morphological classifications to the remaining aperiodic light curves. Another ∼39% of the variable star sample beyond the periodic (low Q) sources are also flux-symmetric, but with a quasiperiodic (moderate Q) or stochastic (high Q) nature. Concerning flux-asymmetric sources, our analysis reveals ∼14% bursters (high negative M) and ∼29% dippers (high positive M). We also investigate the relationship between variability slopes in the g versus g − r color–magnitude diagram, and the light-curve morphological classes. Burster-type objects have shallow slopes, while dipper-type variables tend to have higher slopes that are consistent with extinction-driven variability. Our work is one of the earliest applications of the Q and M metrics to ground-based data. We therefore contrast the Q values of high-cadence and high-precision space-based data, for which these metrics were designed, with Q determinations resulting from degraded space-based light curves that have the cadence and photometric precision characteristic of ground-based data.

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Section: Discussionsupporting

confidence: 84%

Section: Correlation Of Variability Properties With Infrared Excessmentioning

confidence: 99%

Section: Correlation Of Variability Properties With Infrared Excessmentioning

confidence: 99%

Section: Comparison To Q − M Distributions In Other Star-forming Regionsmentioning

confidence: 99%

Section: Appendix B a Lesson Regarding True Periods Near The Observin...mentioning

confidence: 99%

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A Zwicky Transient Facility Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

Hillenbrand¹,

Kiker²,

Gee³

et al. 2022

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The GRAVITY young stellar object survey

Soulain¹,

Perraut²,

Bouvier³

et al. 2023

A&A

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Context. T Tauri stars are known to be the cradle of planet formation. Most exoplanets discovered to date lie at the very inner part of the circumstellar disk (<1 au). The innermost scale of young stellar objects is therefore a compelling region to be addressed, and long-baseline interferometry is a key technique to unveil their mysteries. Aims. We aim to spatially and spectrally resolve the innermost scale (≤1 au) of the young stellar system CI Tau to constrain the inner disk properties and better understand the magnetospheric accretion phenomenon. Methods. The high sensitivity offered by the combination of the four 8-m class telescopes of the Very Large Telescope Interferometer (VLTI) allied with the high spectral resolution (R ~ 4000) of the K-band beam combiner GRAVITY offers a unique capability to probe the sub-au scale of the CI Tau system, tracing both dust (continuum) and gas (Brγ line) emission regions. We developed a physically motivated geometrical model to fit the interferometric observables – visibilities and closure phases (CP) – and constrained the physical properties of the inner dusty disk. The continuum-corrected pure line visibilities have been used to estimate the size of the Hydrogen I Brγ emitting region. Results. From the K-band continuum study, we report a highly inclined (i ~ 70°) resolved inner dusty disk, with an inner edge located at a distance of 21 ± 2 R★ from the central star, which is significantly larger than the dust sublimation radius (Rsub = 4.3 to 8.6 R★). The inner disk appears misaligned compared to the outer disk observed by ALMA and the non-zero closure phase indicates the presence of an asymmetry that could be reproduced with an azimuthally modulated ring with a brighter south-west side. From the differential visibilities across the Brγ line, we resolved the line-emitting region, and measured a size of 4.8- 1.0+ 0.8 R★. Conclusions. The extended inner disk edge compared to the dust sublimation radius is consistent with the claim of an inner planet, CI Tau b, orbiting close in. The inner-outer disk misalignment may be induced by gravitational torques or magnetic warping. The size of the Brγ emitting region is consistent with the magnetospheric accretion process. Assuming it corresponds to the magnetospheric radius, it is significantly smaller than the co-rotation radius (Rcor= 8.8 ± 1.3 R★), which suggests an unstable accretion regime that is consistent with CI Tau being a burster.

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The potential of VLTI observations for the study of circumstellar disk variability

Bensberg,

Kobus,

Wolf

2023

A&A

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Context. A characteristic feature of young stellar objects is their variability, which is caused by a variety of different physical processes. High-resolution interferometric observations in the near- and mid-infrared wavelength ranges spanning multiple epochs allow the detailed study of these processes. Aims. We aim at investigating the expected variations of the interferometric observables connected to changes in the measured photometric fluxes of a typical variable accreting central young stellar object with a circumstellar disk. Methods. We calculated visibilities and closure phases as well as the photometric flux of brightness distributions obtained using 3D Monte Carlo radiative transfer simulations for a model of a circumstellar disk with an accreting central star. Results. Changes in the accretion luminosity of the central object, that is, an accreting pre-main-sequence star, can lead to significant variations in the visibility and closure phase of the star-disk system measured with instruments at the Very Large Telescope Interferometer (VLTI) that can be related to changes in the photometric flux. Taking into account additional effects due to baseline variation, interferometric observations can provide valuable contributions to the understanding of the underlying processes. Additionally, we provide the web application VLTI B-VAR that allows the impact of the hour angle on the visibility and closure phase for customized intensity maps to be estimated.

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The Many-faceted Light Curves of Young Disk-bearing Stars in Taurus as Seen by K2

Cited by 22 publications

References 73 publications

A Zwicky Transient Facility Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

A Zwicky Transient Facility Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

The GRAVITY young stellar object survey

The potential of VLTI observations for the study of circumstellar disk variability

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