Accretion in Young Stellar/Substellar Objects

By J. Muzerolle, L. Hillenbrand, N. Calvet, C. Briceño, L. Hartmann. 2003

329 citations recorded by the source corpus.

We present a study of accretion in a sample of 45 young, low-mass objects in a variety of star-forming regions and young associations, about half of which are likely substellar. Based primarily on the presence of broad, asymmetric Hα emission, we have identified 13 objects (~30% of our sample) that are strong candidates for ongoing accretion. At least three of these are substellar. We do not detect significant continuum veiling in most of the accretors with late spectral types (M5-M7). Accretion shock models show that lack of measurable veiling allows us to place an upper limit to the mass accretion rates of ≲10-10 M☉ yr-1. Using magnetospheric accretion models with appropriate (sub)stellar parameters, we can successfully explain the accretor Hα emission-line profiles and derive quantitative estimates of accretion rates in the range 10-12 M☉ yr-1 < Ṁ < 10-9 M☉ yr-1. There is a clear trend of decreasing accretion rate with stellar mass, with mean accretion rates declining by 3-4 orders of magnitude over ~1-0.05 M☉.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/fa4cc2f4e5d01ccdbc1cce522d51d64da1ee3daf

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In Astronomy and Astrophysics

1. K. Luhman
2. L. Hillenbrand
3. L. Hartmann
4. S. Andrews
5. G. Herczeg
6. N. Calvet
7. Eric Mamajek
8. Ralf Klessen

Citations in the corpus

• Stellar Rotation in Young Clusters: The First 4 Million Years (2004, background): “Our stars are more massive than 0.3 M and, moreover, may have larger accretion rates, because there is evidence that accretion rates increase with mass (e.g., Muzerolle et al. 2003) and decrease with time (e.g., Armitage et al. 2003).”
• An Empirical Criterion to Classify T Tauri Stars and Substellar Analogs Using Low-Resolution Optical Spectroscopy (2003, neutral): “Large open squares correspond to objects with forbidden lines (Zapatero Osorio et al. 2002a; Muzerolle et al. 2003; Briceño et al. 1998; Barrado y Navascués et al. 2004, in prep.)”
• PHOTOEVAPORATION OF CIRCUMSTELLAR DISKS BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET AND X-RAY RADIATION FROM THE CENTRAL STAR (2008, methodology): “We calculate accretiongenerated FUV luminosities from mass-correlated accretion rates (e.g., Gullbring et al. (1998) for accretion-generated FUV; Muzerolle et al. (2003) for mass-dependent accretion rates; see GH08 for details of our procedure).”
• Accretion in brown dwarfs: An infrared view (2004, methodology): “Although, as we will discuss in the following section, in many VLMOs the accretion rate is close to the model sensitivity, this is not the case of TTS (see, e.g., Muzerolle et al. 2003), so that the correlation we find neglecting upper limits is probably somewhat shallower than the true one.”
• Star and Protoplanetary Disk Properties in Orion's Suburbs (2009, methodology): “Power law fits of the formṀacc∝Mα∗ have yielded values in the range 1.0−2.1 for the exponentα (White & Basri 2003; Muzerolle et al. 2003; Calvet et al. 2004; Muzerolle et al. 2005; Mohanty et al. 2005; Natta et al. 2006; Garcia Lopez et al. 2006; Herczeg & Hillenbrand 2008; Gatti et al. 2008).”
• Theory of Star Formation (2007, background): “A recent compilation of observations (White & Basri, 2003; Muzerolle et al., 2003; Calvet et al., 2004) shows an approximate dependence of the accretion rate on stellar mass Ṁdisk ∝ m2∗, although with considerable scatter (Muzerolle et al., 2005).”
• A Survey and Analysis of Spitzer Infrared Spectrograph Spectra of T Tauri Stars in Taurus (2006, methodology): “…width of their H emission line (EW[H ]): CTTSs have broad and asymmetric H line profiles, which are generated in the magnetospheric accretion flows (Muzerolle et al. 2003b), resulting in an EW[H ] larger than 10 8, while WTTSs have an EW[H ] of less than 10 8; in WTTSs, strong surface magnetic…”
• 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).”
• TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR (2009, background): “This scaling is motivated by observations of a correlation between the accretion rate and central star mass, Ṁacc ∝ M2∗ (Muzerolle et al 2003, Natta et al 2004, Calvet et al. 2004, Muzerolle et al 2005, Natta et al 2006).”
• Accretion onto Pre-Main-Sequence Stars (2016, background): “…the ultraviolet spectra of low-mass and intermediate-mass T Tauri stars, brown dwarfs, and some Herbig Ae/Be (HAeBe) stars reasonably well (Calvet & Gullbring 1998; Gullbring et al. 2000; Ardila & Basri 2000; Muzerolle et al. 2000, 2003; Calvet 2004; Muzerolle et al. 2004; Mendigutia et al. 2011).”
• X-ray emission from T Tauri stars and the role of accretion: inferences from the XMM-Newton extended survey of the Taurus molecular cloud (2006, background): “Similarly, Muzerolle et al. (2003) and Muzerolle et al. (2005) found Ṁ ∝ M2 and Ṁ ∝ M2.”
• Accretion Rates in Herbig Ae stars (2006, background): “Results can be found, e.g., in Gullbring et al. 1998, Muzerolle et al. (1998, 2003, 2005), White and Ghez (2001), Natta et al. (2004, 2006), Mohanty et al. (2005).”
• Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, background): “where α ≈ 1.8, however, with a large scatter of about one order of magnitude (Muzerolle et al. 2003; Natta et al. 2006).”