X-Shooter study of accretion in Chamaeleon I

Manara, C. F.; Fedele, D.; Herczeg, Gregory J.; Teixeira, P. S.

doi:10.1051/0004-6361/201527224

Cited by 126 publications

(187 citation statements)

References 73 publications

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“…Among the sources within our sample with measured accretion rates (Hartmann et al 1998;Antoniucci et al 2011;Robberto et al 2012;Frasca et al 2015;Manara et al 2016), typical L acc /L * ∼0.1-0.4, consistent with surveys of other low-mass star-forming regions (e.g., Antoniucci et al 2014). Some variation is seen in the accretion rate as measured by different surveys, but part of this may be due to differences in methodologies for deriving the accretion rate rather than real fluctuations.…”

Section: Discussionsupporting

confidence: 80%

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Spitzer Observations of Long-Term Infrared Variability Among Young Stellar Objects in Chamaeleon I

Flaherty

DeMarchi

Muzerolle

et al. 2016

ApJ

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Infrared variability is common among young stellar objects, with surveys finding daily to weekly fluctuations of a few tenths of a magnitude. Space-based observations can produce highly sampled infrared light curves, but are often limited to total baselines of about 1 month due to the orientation of the spacecraft. Here we present observations of the Chameleon I cluster, whose low declination makes it observable by the Spitzer Space Telescope over a 200-day period. We observe 30 young stellar objects with a daily cadence to better sample variability on timescales of months. We find that such variability is common, occurring in ∼80% of the detected cluster members. The change in [3.6]-[4.5] color over 200 days for many of the sources falls between that expected for extinction and fluctuations in disk emission. With our high cadence and long baseline we can derive power spectral density curves covering two orders of magnitude in frequency and find significant power at low frequencies, up to the boundaries of our 200-day survey. Such long timescales are difficult to explain with variations driven by the interaction between the disk and stellar magnetic field, which has a dynamical timescale of days to weeks. The most likely explanation is either structural or temperature fluctuations spread throughout the inner ∼0.5 au of the disk, suggesting that the intrinsic dust structure is highly dynamic.

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Section: Discussionsupporting

confidence: 80%

“…e No spectroscopic binary companion detected by Nguyen et al (2012), with sensitivity down to ∼0.1 M e over 60-day periods. f Manara et al (2016). g Frasca et al (2015).…”

Section: Finding Variable Starsmentioning

confidence: 99%

Spitzer Observations of Long-Term Infrared Variability Among Young Stellar Objects in Chamaeleon I

Flaherty

DeMarchi

Muzerolle

et al. 2016

ApJ

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“…For multiple-star systems, the adopted stellar mass is the mass of the primary, following Pascucci et al (2016). Accretion rates are obtained from Manara et al (2016aManara et al ( , 2017 and are adjusted for updated luminosities and stellar radii, which are increased for the adopted distance, and for the masses used by Pascucci et al (2016). O detections.…”

Section: Correlations Of Star and Disk Properties With Co Line Fluxesmentioning

confidence: 99%

An ALMA Survey of CO Isotopologue Emission from Protoplanetary Disks in Chamaeleon I

Long

Herczeg

Pascucci

et al. 2017

ApJ

137

142

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The mass of a protoplanetary disk limits the formation and future growth of any planet. Masses of protoplanetary disks are usually calculated from measurements of the dust continuum emission by assuming an interstellar gas-todust ratio. To investigate the utility of CO as an alternate probe of disk mass, we use ALMA to survey 13 CO and C 18 O J=3-2 line emission from a sample of 93 protoplanetary disks around stars and brown dwarfs with masses from M 0.03 to 2  in the nearby Chamaeleon I star-forming region. We detect 13 CO emission from 17 sources and C 18 O from only one source. Gas masses for disks are then estimated by comparing the CO line luminosities to results from published disk models that include CO freeze-out and isotope-selective photodissociation. Under the assumption of a typical interstellar medium CO-to-H 2 ratio of 10 −4 , the resulting gas masses are implausibly low, with an average gas mass of ∼0.05 M Jup as inferred from the average flux of stacked 13 CO lines. The low gas masses and gas-to-dust ratios for Cha I disks are both consistent with similar results from disks in the Lupus starforming region. The faint CO line emission may instead be explained if disks have much higher gas masses, but freeze-out of CO or complex C-bearing molecules is underestimated in disk models. The conversion of CO flux to CO gas mass also suffers from uncertainties in disk structures, which could affect gas temperatures. CO emission lines will only be a good tracer of the disk mass when models for C and CO depletion are confirmed to be accurate.

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“…The data set of Chamaeleon I is based on the ALMA survey presented by Pascucci et al (2016) and the X-Shooter survey presented by Manara et al (2016aManara et al ( , 2017.…”

Section: Chamaeleon Imentioning

confidence: 99%

Constraints from Dust Mass and Mass Accretion Rate Measurements on Angular Momentum Transport in Protoplanetary Disks

Mulders

Pascucci

Manara

et al. 2017

ApJ

123

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In this paper, we investigate the relation between disk mass and mass accretion rate to constrain the mechanism of angular momentum transport in protoplanetary disks. We find a correlation between dust disk mass and mass accretion rate in Chamaeleon I with a slope that is close to linear, similar to the one recently identified in Lupus. We investigate the effect of stellar mass and find that the intrinsic scatter around the best-fit M dust - M andṀ acc - M relations is uncorrelated. We simulate synthetic observations of an ensemble of evolving disks using a Monte Carlo approach and find that disks with a constant α viscosity can fit the observed relations between dust mass, mass accretion rate, and stellar mass but overpredict the strength of the correlation between disk mass and mass accretion rate when using standard initial conditions. We find two possible solutions. In the first one, the observed scatter in M dust andṀ acc is not primordial, but arises from additional physical processes or uncertainties in estimating the disk gas mass. Most likely grain growth and radial drift affect the observable dust mass, while variability on large timescales affects the mass accretion rates. In the second scenario, the observed scatter is primordial, but disks have not evolved substantially at the age of Lupus and Chamaeleon I owing to a low viscosity or a large initial disk radius. More accurate estimates of the disk mass and gas disk sizes in a large sample of protoplanetary disks, through either direct observations of the gas or spatially resolved multiwavelength observations of the dust with ALMA, are needed to discriminate between both scenarios or to constrain alternative angular momentum transport mechanisms such as MHD disk winds.

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X-Shooter study of accretion in Chamaeleon I

Cited by 126 publications

References 73 publications

Spitzer Observations of Long-Term Infrared Variability Among Young Stellar Objects in Chamaeleon I

Spitzer Observations of Long-Term Infrared Variability Among Young Stellar Objects in Chamaeleon I

An ALMA Survey of CO Isotopologue Emission from Protoplanetary Disks in Chamaeleon I

Constraints from Dust Mass and Mass Accretion Rate Measurements on Angular Momentum Transport in Protoplanetary Disks

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