review & update of dipper systems Megan Ansdell Flatiron - - PowerPoint PPT Presentation

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review amp update of dipper systems
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review & update of dipper systems Megan Ansdell Flatiron - - PowerPoint PPT Presentation

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review & update of dipper systems Megan Ansdell Flatiron Institute CCA/CCM 2nd International Workshop on UXORs St. Petersburg, 3 Oct. 2019 what are dippers systems? exhibit dimming events 1.10 Normalized Flux 0.95 deep

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SLIDE 1

review & update of dipper systems

Megan Ansdell

Flatiron Institute CCA/CCM

2nd International Workshop on UXORs 


  • St. Petersburg, 3 Oct. 2019
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SLIDE 2

what are “dippers” systems?

Ansdell et al. 2016a

0.50 0.65 0.80 0.95 1.10 Normalized Flux

EPIC 204137184

0.85 0.90 0.95 1.00 1.05 Normalized Flux

EPIC 203937317

2060 2080 2100 2120 2140 BJD-2454833 0.80 0.85 0.90 0.95 1.00 1.05 Normalized Flux

EPIC 205519771

0.0 0.2 0.4 0.6 0.8 1.0 Phase

quasi-periodic 
 “AA Tau-like” quasi-periodic aperiodic

CoRoT + K2 young stars + disks

  • 1-10 Myr (normal) TTauri stars
  • common (30% of YSOs)
  • host protoplanetary disks
  • deep (> 10 % in flux)
  • moderate-duration (1 day)
  • quasi-periodic or aperiodic


(QP ~ stellar rotation period)

exhibit dimming events

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SLIDE 3

how are “dippers” different from UXORs?

UXORs Dippers

PERIODICITY

aperiodic aperiodic 


  • r quasi-periodic

DIP DURATION

weeks - months 0.5 - 2 days

DIP DEPTH

1 - 3 mags 0.1 - 1 mags

STELLAR HOSTS

Herbigs T Tauri stars

harder to explain with single/unified mechanism?

➜

difficult to schedule simultaneous observations

➜

need space-based telescopes to detect variability

➜

more common, but fainter; harder follow up observing

➜

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SLIDE 4

what causes dippers?

inner warp in edge-on accretion disk

nearly edge-on (70 deg) disk

Bouvier+1999

inclined B-field co-rotation radius

McGinnis+2015 Kurosawa & Romanova 2013

stable accretion

quasi-periodic

unstable accretion

aperiodic

➜ ➜

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SLIDE 5

what causes dippers?

Bodman+2017

  • co-rotation radius > sublimation radius

for low-mass (K/M-type) stars

  • co-rotation radius ~ B-field truncation radius

allows material to flow up B-field lines

  • inclined B-field axis enables moderate disk

inclinations to exhibit dipper behavior

need measurements of B , 흻, Ω, Ṁacc to confirm

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SLIDE 6

most dippers are not significantly accreting

Paɣ emission:

  • 44% of K2 dippers
  • 97% of CTTS (Edwards+06)

most are WTTS based on H흰 emission weak or no accretion based on Pa힬 emission

White & Basri 2003 Edwards+2006

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SLIDE 7

J1604: misaligned inner disk from inclined companion

Marino+2015 (HD152527) Takami+2014, Pinilla+2018

➜

Early search of ALMA archive suggested not by turning up face-on, edge-on, and intermediate inclination dipper disks

are dipper disks really edge-on?

Ansdell et al. 2016b

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SLIDE 8

GPU-accelerated Python library for fitting radio interferometry visibilities

GALARIO

Tazarri+2018

emcee

MCMC sampler in Python for Bayesian parameter estimation

Forman-Mackey+2013

uncertainties & posterior distributions

measuring outer disk inclinations with ALMA

➜ +

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SLIDE 9

24 dippers in USco & 흆 Oph dippers found in K2 light curves

  • uter disks

resolved by ALMA

➜

+

Ansdell+2016a Hedges+2018 Cody & Hillenbrand 2018 Ansdelll (subm.) ALMA archive

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SLIDE 10

Ansdell et al. (subm.)

MC sampling of posterior distributions

dippers exhibit an isotropic idisk distribution

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SLIDE 11

accretion-driven disc warp vertical disc instability dusty disc winds broken inner disc

EPIC id

203937317 7 disc inclination too low disc inclination too low no resolved cavity disc inclination too low 204638512 8 204281213 19 203770559 27 no resolved cavity 205345560 29 204630363 38 204864076 45 no resolved cavity 204176565 47 203936815 47 203950167 48 204142243 48 no resolved cavity 203962599 52 205151387 54 203860592 54 205238942 56 204489514 59 no resolved cavity 204514548 61 203895983 63 203843911 66 203824153 67 204399980 70 204211116 71 205080616 71 203850058 84

multiple (+new) mechanisms needed to explain dippers?

Ansdell et al. (subm.)

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SLIDE 12

DSHARP observations of dipper disks

Andrews et al. 2018, Huang et al. 2018

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SLIDE 13
  • diverse disk morphologies

down to ~ 5au scales

  • diversity reflects larger

DSHARP sample

  • other DSHARP disks with K2

light curves are not dippers

DSHARP observations of dipper disks

Andrews et al. 2018, Huang et al. 2018

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SLIDE 14

finding intermediate-aged dippers with TESS

TESS covers the entire sky, including nearby YMGs (10- 150 Myr)

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SLIDE 15

finding intermediate-aged dippers with TESS

Gaidos et al. 2019

HD 240779 [1M⦿, 125 Myr]

  • many of the dipper mechanisms (e.g, accretion-driven inner disk warps) ruled out
  • can be explained by disrupted ~100 km planetesimal due to tides or stellar irradiation?
  • will give insight into final phase of rocky planet formation (30 TESS dippers already identified)
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SLIDE 16

Summary

  • Dipper disks are not biased toward nearly edge-on inclinations
  • Dippers have an isotropic outer disk inclination distribution and

exhibit a range of morphologies echoing the general disk population

  • This suggests that multiple mechanisms may be required to explain

the dipper phenomenon (inner warps, disk winds, inclined planets)

  • More broady, this also suggests that the geometry and morpholoy
  • uter disk is completely unrelated to the dynamic inner disk