Accretion in brown dwarfs: An infrared view

By A. Natta, L. Testi, J. Muzerolle, S. Randich, F. Comerón, P. Persi. 2004

332 citations recorded by the source corpus.

This paper presents a study of the accretion properties of 19 very low mass objects ($M_\star$~ $0.01{-}0.1$ $M_\odot$) in the regions Chamaeleon I and ρ  Oph. For 8 objects we obtained high resolution H α  profiles and determined mass accretion rate $\dot M_{\rm ac}$  and accretion luminosity L ac . Pa β  is detected in emission in 7 of the 10 ρ  Oph objects, but only in one in Cha I. Using objects for which we have both a determination of L ac  from H α and a Pa β  detection, we show that the correlation between the Pa β  luminosity and luminosity L ac , found by Muzerolle et al. ([CITE]) for T Tauri stars in Taurus, extends to objects with mass ~0.03 $M_\odot$; L (Pa β ) can be used to measure L ac  also in the substellar regime. The results were less conclusive for Br γ , which was detected only in 2 objects, neither of which had an H α  estimate of $\dot M_{\rm ac}$. Using the relation between L (Pa β ) and L ac  we determined the accretion rate for all the objects in our sample (including those with no H α spectrum), more than doubling the number of substellar objects with known $\dot M_{\rm ac}$. When plotted as a function of the mass of the central object together with data from the literature, our results confirm the trend of lower $\dot M_{\rm ac}$ for lower $M_\star$, although with a large spread. Some of the spread is probably due to an age effect; our very young objects in ρ  Oph have on average an accretion rate at least one order of magnitude higher than objects of similar mass in older regions. As a side product, we found that the width of H α  measured at 10% peak intensity is not only a qualitative indicator of the accreting nature of very low mass objects, but can be used to obtain a quantitative, although not very accurate, estimate of $\dot M_{\rm ac}$ over a large mass range, from T Tauri stars to brown dwarfs. Finally, we found that some of our objects show evidence of mass-loss in their optical spectra.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b2300f4b9dfea7d94a887cd0c513311d4e8434e7

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In Astronomy and Astrophysics

1. K. Luhman
2. G. Herczeg
3. L. Hillenbrand
4. L. Hartmann
5. N. Calvet
6. A. Kraus
7. L. Testi
8. S. Andrews

In Instrumentation

1. K. Luhman
2. L. Hillenbrand
3. G. Herczeg
4. A. Natta
5. L. Testi
6. A. Kraus
7. Michael J. Ireland
8. L. Hartmann

Citations in the corpus

• Timescale of mass accretion in pre-main-sequence stars (2009, background): “This criterion is validdown to a mass accretion rate of 10−10 ÷ 10−12 M⊙yr−1 (Natta et al. 2004).”
• UV Excess Measures of Accretion onto Young Very Low Mass Stars and Brown Dwarfs (2008, methodology): “Excess IR emission indicates the presence of disks around some of these very low-mass objects2 (e.g. Muzerolle et al. 2003; 1 Caltech, MC105-24, 1200 E. California Blvd., Pasadena, CA 91125 Jayawardhana et al. 2003; Natta et al. 2004).”
• Demographics of Transition Objects (2007, methodology): “They have been used, for example, to demonstrate correlations between Ṁ∗ and stellar mass (e.g., Muzerolle et al. 2003; Natta et al. 2004) as well as Ṁ∗ and age (e.g., Sicilia-Aguilar et al. 2005).”
• Accretion onto Pre-Main-Sequence Stars (2016, background): “…lines as secondary accretion rate measurements, where a line luminosity or shape is converted to an accretion luminosity on the basis of correlations from stars where both are measured (e.g., Muzerolle et al. 1998, Natta et al. 2004, Mohanty et al. 2005, Dahm 2008, Herczeg & Hillenbrand 2008).”
• Toward a Deterministic Model of Planetary Formation. III. Mass Distribution of Short-Period Planets around Stars of Various Masses (2005, background): “…estimates of disk mass both in gas and dust are difficult to obtain for the inadequate sensitivity of existing observational instruments, the disk accretion rate Ṁ can be inferred from the Hα line profiles (Muzerolle et al. 2003; Natta et al. 2004) such that Ṁ ∝ M2∗ with a large dispersion.”
• THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION (2011, background): “Accretion signatures as inferred from a UV excess at .4000 Å(Balmer jump of F 3600Å /F 4000Å > 0.5; Herczeg & Hillenbrand 2008), or broadened Hα emission (v10% > 200 km s −1; e.g., Natta et al. 2004).”
• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation (2008, background): “10−8M⊙; e.g. Natta et al. 2004; Muzerolle et al. 2005; Mohanty et al. 2005; Herczeg & Hillenbrand 2008).”
• The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, methodology): “Additional accretion diagnostics have included Ca II (Mohanty, Jayawardhana & Basri 2005), near-IR hydrogen transitions (Natta et al. 2004), and optical continuum veiling (White & Basri 2003).”
• Measuring Accretion in Young Substellar Objects: Approaching the Planetary Mass Regime (2005, background): “We note that the accretion rate measurements for low-mass members of Ophiuchus from Natta et al. (2004) appear to be larger on average by about a factor of 5–10 than those in Taurus, Cha I, and IC 348.”
• ACCRETION RATES FOR T TAURI STARS USING NEARLY SIMULTANEOUS ULTRAVIOLET AND OPTICAL SPECTRA (2013, methodology): “Both the equivalent width of Hα, EW(Hα), and the width of Hα at 10% of the maximum flux are often used as accretion proxies (White & Basri 2003; Natta et al. 2004).”
• The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs (2005, background): “So do spectroscopic signatures of disk accretion, such as broad, asymmetric H lines (Jayawardhana et al. 2002, 2003b, hereafter JMB02, JMB03; Muzerolle et al. 2003, hereafter M03; Natta et al. 2004, hereafter N04).”
• Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, background): “Typical accretion rates are on the order of 3×10−8 M yr−1 for a one solar mass star Page 13 of 18 (e.g. Natta et al. 2004; Muzerolle et al. 2005; Lopez et al. 2006; Gatti et al. 2006, 2008), while the mass of the disk is typically on the order of 10−2 M .”
• Accretion in the ρ-Ophiuchi pre-main sequence stars (2006, methodology): “The squares are those for which also Paβ data exist; because none of the BDs in Taurus has a published J-band spectrum, we have added the BDs in Ophiuchus and Chamaeleon for which Natta et al. (2004) have measured Ṁacc from model fitting of the Hα profiles.”
• Launching of conical winds and axial jets from the disc–magnetosphere boundary: axisymmetric and 3D simulations (2009, background): “Clear signs of CTTS-like magnetospheric accretion (broad spectral lines with full-widths of v > 200 km s−1) were reported earlier for a number of young BDs (e.g. Natta et al. 2004).”