Abstract
Abstract At least half of a protostar’s mass is accreted in the Class 0 phase, when the central protostar is deeply embedded in a dense, infalling envelope. We present the first systematic search for outbursts from Class 0 protostars in the Orion clouds. Using photometry from Spitzer/IRAC spanning 2004 to 2017, we detect three outbursts from Class 0 protostars with ≥2 mag changes at 3.6 or 4.5 μm. This is comparable to the magnitude change of a known protostellar FU Ori outburst. Two are newly detected bursts from the protostars HOPS 12 and 124. The number of detections implies that Class 0 protostars burst every 438 yr, with a 95% confidence interval of 161 to 1884 yr. Combining Spitzer and WISE/NEOWISE data spanning 2004–2019, we show that the bursts persist for more than nine years with significant variability during each burst. Finally, we use 19–100 μm photometry from SOFIA, Spitzer, and Herschel to measure the amplitudes of the bursts. Based on the burst interval, a duration of 15 yr, and the range of observed amplitudes, 3%–100% of the mass accretion during the Class 0 phase occurs during bursts. In total, we show that bursts from Class 0 protostars are as frequent, or even more frequent, than those from more evolved protostars. This is consistent with bursts being driven by instabilities in disks triggered by rapid mass infall. Furthermore, we find that bursts may be a significant, if not dominant, mode of mass accretion during the Class 0 phase.
Highlights
The outburst of Herschel Orion Protostar Survey (HOPS) 383, identified in multi-epoch Spitzer and WISE observations, was the first detection of a luminous outburst toward a Class 0 protostar (Safron et al 2015)
The outburst of HOPS 383, identified in multi-epoch Spitzer and WISE observations, was the first detection of a luminous outburst toward a Class 0 protostar (Safron et al 2015). This outburst appears similar to the outbursts driven by rapid increases in mass accretion detected toward more evolved protostars
We will show that protostars with smaller amplitude variations exhibit a more diverse range of behaviors, including bursts, fluctuations and fades (Zakri W. et al 2021, in preparation; see Park et al 2021)
Summary
The outburst of HOPS 383, identified in multi-epoch Spitzer and WISE observations, was the first detection of a luminous outburst toward a Class 0 protostar (Safron et al 2015). This outburst appears similar to the outbursts driven by rapid increases in mass accretion detected toward more evolved protostars. If outbursts are common for Class 0 protostars, they may contribute a substantial fraction of a star’s mass.
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