Transcript PPTX

Variability of young
stars with LSST
Gregory J. Herczeg
KIAA
Star Formation:
ISM/Molecular Clouds
Pre-main sequence stellar evolution
(low-mass case)
Classical T Tauri Stars
HD141569, Clampin et al.
From Visser et al.,
in prep
Morphology of a classical T Tauri star
Dullemond et al., PPV
Morphology of a classical T Tauri star
Luminosity Problem
Lbol
(Kenyon et al. 1990; Dunham, Evans, et al. 2009/2010)
Tbol
• Luminosities much lower than predicted from steady infall
• Possible solution: most stellar mass accretes during rare outbursts
Young Star Outbursts
Miller et al. 2010
Palomar Transient Factory
• FUors and EXors
• Very rare
- ~10 confirmed FUors
• 5-8 magnitude increase
in luminosity
• EXors: 1 year duration
• FU Ori: 1937 outburst is
still ongoing
1893
Accretion Variability: EX Lup
11
14
1941
McLaughlin (1946)
2008 Outburst
of EX Lup
• 5-magnitude brightness
– 2 x 10-7 Msol/yr
– 100 times higher than
quiescence
• Lasted about half a year
– Similar strength, duration
as 1955 outburst
Aspin et al. 2010
Accretion-powered jets
• Episodic mass ejection: related to accretion
events? (e.g., Reipurth et al. 1989)
Accretion Histories
• Rate and strength of FUOr/EXOr outbursts
– Limited to end state of accretion
– Class 0/I: JCMT/SCUBA2?
• Identify physical cause of outbursts
– Gravitational Instability + MRI (Zhu et al. 2010)
– Multiple star/disk interactions (Reipurth et al.)
– Thermal Instability (Martin et al. 2010)
– Gravitational Clumping (Vorobyov & Basu 2005)
Optical accretion
diagnostics
Accretion columns
of AA Tau
(Bouvier et al. 2007)
V-band periodicity
H-alpha line profiles
Variable accretion onto
young star with disk
(Herczeg et al. in prep)
COROT observations of NGC 2264
(Alencar, Bouvier, et al. 2010)
NO DISK
DISK ACCRETION
Stochastic variability: changes in star-disk interaction
Longer term variability: disk instabilities
Disks Warps
(e.g., Herbst et al. 2000s; Plavchan et al. 2008)
I-magnitude through
5 different seasons
Ongoing SF variability programs
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COROT observations of NGC 2264 (Alencar et al.)
YSOVar: Warm Spitzer near-IR monitoring (Stauffer et al.)
Palomar Transit Factory (Hillenbrand, Covey)
VYSSOS: daily monitoring of many SF regions (P.I. Reipurth;
not yet ongoing, uncertain future)
• PAN-STARRS
Young star variability
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Accretion history (for optically visible objects)
Accretion variability: unbiased assessment, timescales
Rotational modulation (space-based monitoring best)
Disk warps: planet-induced, star/disk interactions
Light echoes: outburst bouncing off envelope, disk
Hot spots of magnetically active M-dwarfs
Eclipsing binaries as test of stellar evolution tracks
LSST, not variability (covered by VISTA?)
• Low-metallicity galactic star formation (Yasui et al. 2009)
• Extinction mapping
• Young populations/IMF (need complementary spectra)
Formation of youngest disks
(Herczeg et al. 2011)
• VLT/CRIRES M-band spectra of
CO emission
- R = 100,000
- Usually behind AO
• Measure CO emission/profiles
from disks around protostars
• Disks: either present or absent
Searching for growth of disks
(Herczeg et al. 2012)
Watson et al. 2007, Nature
Spitzer/IRS spectra: hot water
emission from envelope/disk
accretion shock?
Herschel far-IR spectral imaging:
hot water emission from the
outflow, not the disk
UV Excess Measures of Accretion
(Herczeg, in prep)
• Low-resolution optical spectra of
300 T Tauri stars
– Palomar and Keck
– 3200-9000 A, R=1000
– Largest U-band spectroscopic
sample of T Tauri stars to date
• Most accurate method to measure
accretion rate
- Simultaneous extinction,
spectral type
• 80 more spectra from VLT/X-Shooter
• 3000 A – 2.5 microns at
R=10,000
Disks, Accretion and Outflows from
T Tauri stars (DAO of Tau)
(P.I. Herczeg)
• HST/FUV spectra
– 1150-1800 A
– R=20,000
– 30 stars, 111 orbits
total)
• Hot emission from
accretion shock
• Molecular emission
from disks
• Wind absorption lines
Discovery of FUV CO Emission from T
Tauri stars, France et al. (2011)
Variability of young stars
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Accretion history for visible objects
Accretion variability: unbiased assessment, timescales
Rotational modulation (space-based monitoring best)
Disk warps: planet-induced, star/disk interactions
Light echoes: outburst bouncing off envelope structures
Hot spots of magnetically active M-dwarfs
Eclipsing binaries as test of stellar evolution tracks
LSST, not variability
• Low-metallicity SF (e.g., Yasui et al.)
• Extinction mapping
• Young populations: need spectra (SpT, gravity, better ages)