Kavli Affiliate: Gregory Herczeg
| First 5 Authors: Patrick D. Sheehan, Doug Johnstone, Carlos Contreras Peña, Seonjae Lee, Gregory Herczeg
| Summary:
The JCMT Transient Survey recently discovered that the Class 0 protostar HOPS
358 decreased in 350 GHz continuum brightness by $sim25$% over the course of
four years before brightening again for the next four. The JCMT lightcurve can
be fit by a long timescale dip lasting roughly eight years. A shorter timescale
periodicity is also apparent with a period of 1.75 years and a small 3%
amplitude. NEOWise monitoring reveals that the mid-IR wavelength brightness of
HOPS 358 follows a similar long-term pattern in time. Here, we present a study
of nine epochs of ALMA observations of HOPS 358 taken over the course of the
decline and subsequent rise in brightness seen with the JCMT to test whether
the variation seen on $sim15"$ scales, covering both disk and envelope, is
also observed on smaller, $<1"$ scales that primarily probe HOPS 358’s
protostellar disk. We detect both HOPS 358 and its southern companion, HOPS
358B, in our ALMA observations, and find that at least one of the two is
varying. Assuming that HOPS 358 is the variable, the light curve has the same
shape as that found by the JCMT. Additionally, our high resolution ALMA imaging
of HOPS 358 reveals that the disk is warped, with a $16^{circ}$ warp at a disk
radius of 35 au, about halfway through the extent of the disk. The physical
origin of the warp along with how it relates to the variability seen towards
HOPS 358, however, remain unclear.
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