UV Excess Measures of Accretion onto Young Very Low Mass Stars and Brown Dwarfs

By G. Herczeg, L. Hillenbrand. 2008

290 citations recorded by the source corpus.

Low-resolution spectra from 3000 to 9000 Å of young low-mass stars and brown dwarfs were obtained with LRIS on Keck I. The excess UV and optical emission arising in the Balmer and Paschen continua yields mass accretion rates ranging from 2 × 10−12 to 10−8 M☉ yr−1. These results are compared with HST STIS spectra of roughly solar-mass accretors with accretion rates that range from 2 × 10−10 to 5 × 10−8 M☉ yr−1. The weak photospheric emission from M dwarfs at <4000 Å leads to a higher contrast between the accretion and photospheric emission relative to higher mass counterparts. The mass accretion rates measured here are systematically ~4-7 times larger than those from Hα emission line profiles, with a difference that is consistent with but unlikely to be explained by the uncertainty in both methods. The accretion luminosity correlates well with many line luminosities, including high Balmer and many He I lines. Correlations of the accretion rate with Hα 10% width and line fluxes show a large amount of scatter. Our results and previous accretion rate measurements suggest that Ṁ ∝ M1.87 ± 0.26 for accretors in the Taurus molecular cloud.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/69b042f069d3790fe06f47ec7cfa3ca1bfc365ef

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In Astronomy and Astrophysics

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

Citations in the corpus

• A spectroscopic survey of Herbig Ae/Be stars with X-shooter – I. Stellar parameters and accretion rates (2015, background): “This UV-excess has been measured in both brown dwarfs (Herczeg & Hillenbrand 2008; Herczeg, Cruz & Hillenbrand 2009; Rigliaco et al. 2012) and CTTs (Calvet et al. 2004; Gullbring et al. 2000; Calvet et al. 2004; Ingleby et al. 2013).”
• 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 MASS DEPENDENCE BETWEEN PROTOPLANETARY DISKS AND THEIR STELLAR HOSTS (2013, background): “…al. 2001; Briceño et al. 2002; Vieira et al. 2003; Beskrovnaya & Pogodin 2004; Luhman 2004; Kraus et al. 2006; Guieu et al. 2006; Audard et al. 2007; Herczeg & Hillenbrand 2008; Luhman et al. 2009b; Duchêne et al. 2010), as well as the Sloan Digital Sky Survey (SDSS–8; Adelman-McCarthy & et al.…”
• ACCRETION RATES FOR T TAURI STARS USING NEARLY SIMULTANEOUS ULTRAVIOLET AND OPTICAL SPECTRA (2013, background): “Hβ is less often used to trace accretion than Hα but has been shown to correlate with Ṁ (Muzerolle et al. 2001; Herczeg & Hillenbrand 2008; Fang et al. 2009).”
• A STEEPER THAN LINEAR DISK MASS–STELLAR MASS SCALING RELATION (2016, background): “For these three young regions the relation is close to a power law of two: ˙ ( )*µM M 1.9 0.3 for Taurus (Herczeg & Hillenbrand 2008), ˙ ( )*µM M 1.8 0.2 for Lupus (Alcalá et al. 2014), and ˙ ( )*µM M 1.7 0.4 for ChamaeleonI (Manara et al. 2016a).”
• Dust properties of protoplanetary disks in the Taurus-Auriga star forming region from millimeter wavelengths (2009, methodology): “The accretion luminosity was then calculated from the excess Balmer continuum emission, following the method described in Herczeg & Hillenbrand (2008).”
• Accretion onto Pre-Main-Sequence Stars (2016, methodology): “…versus stellar mass and (b) age for accretion rates obtained from spectroscopic measurements of the Balmer continuum (red circles from Calvet 2004, Herczeg & Hillenbrand 2008, Herczeg et al. 2009, Rigliaco et al. 2012, Ingleby et al. 2013, Alcala et al. 2014, Fairlamb et al. 2015); from…”
• Three Radial Gaps in the Disk of TW Hydrae Imaged with SPHERE (2016, background): “We also show the speed at which the gas would move inward to sustain the current accretion rate, for which we adopt Ṁacc = 1.5× 10−9 M yr−1 (Herczeg & Hillenbrand 2008) but note that this rate is temporally variable.”
• TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA (2013, methodology): “…is given by the standard deviation of the flux. χflare is similar to the Balmer jump, J, that has been measured from T Tauri star spectra (Valenti et al. 1993; Herczeg & Hillenbrand 2008) and also in previous M dwarf flare studies in the blue to derive electron temperatures assuming an isothermal,…”
• Timescale of mass accretion in pre-main-sequence stars (2009, background): “In order to decipher the nature of these sources we also investigated the presence of other emission lines which are associated with mass accretion (e.g. Hei 5876Å, 6678Å; e.g. Beristain et al. 2001; Herczeg & Hillenbrand 2008).”
• AN OPTICAL SPECTROSCOPIC STUDY OF T TAURI STARS. I. PHOTOSPHERIC PROPERTIES (2014, background): “The entire sample of the 2006 Keck observations was published in Herczeg & Hillenbrand (2008).”
• The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, background): “…these various diagnostics are correlated with stellar mass as Ṁ ∝ M2 for the full range of masses across which they have been measured (M ∼ 0.02–2 M⊙, Herczeg & Hillenbrand 2008; Mohanty, Jayawardhana & Basri 2005; Muzerolle et al. 2005; Natta, Testi & Randich 2006), although it has been…”
• 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).”
• 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).”
• Accretion disks in luminous young stellar objects (2015, background): “The extra continuum emission is easily distinguishable from the cool atmospheric emission of late-type stars (Herbst et al., 1994) and it can be identified in the weakest magneto-spheric accretors (Herczeg & Hillenbrand, 2008) by means of excess UV and optical light.”