Irregular Dust Features around Intermediate-mass Young Stars with GPI: Signs of Youth or Misaligned Disks?

Abstract

We are undertaking a large survey of over thirty disks using the Gemini Planet Imager (GPI) to see whether the observed dust structures match spectral energy distribution (SED) predictions and have any correlation with stellar properties. GPI can observe near-infrared light scattered from dust in circumstellar environments using high-resolution Polarimetric Differential Imaging (PDI) with coronagraphy and adaptive optics. The data have been taken in J and H bands over two years, with inner working angles of 0.08 " and 0.11 " respectively. Ahead of the release of the complete survey results, here we present five objects with extended and irregular dust structures within 2 " of the central star. These objects are: FU Ori; MWC 789; HD 45677; Hen 3-365; and HD 139614. The observed structures are consistent with each object being a pre-main-sequence star with protoplanetary dust. The five objects' circumstellar environments could result from extreme youth and complex initial conditions, from asymmetric scattering patterns due to shadows cast by misaligned disks, or in some cases from interactions with companions. We see complex U φ structures in most objects that could indicate multiple scattering or result from the illumination of companions. Specific key findings include the first high-contrast observation of MWC 789 revealing a newly-discovered companion candidate and arc, and two faint companion candidates around Hen 3-365. These two objects should be observed further to confirm whether the companion candidates are co-moving. Further observations and modeling are required to determine the causes of the structures.

Viscous heating in the disk of the outbursting star FU Orionis

“…The limitations in uvcoverage of earlier interferometric studies resulted likely also in the wide spread of minor axis position angle estimates that range from 19 • ± 12 (Quanz et al 2006), 47 •+7 −11 (Malbet et al 2005). In addition, many literature values are at odds with the tentative detection of a jet/outflow detected on larger scales by Takami et al (2018) and Laws et al (2020) (features C and D respectively). The putative jet/outflow feature was detected in scattered light imagery obtained with Subaru and GPI, respectively.…”

“…The vertical profile of the disk schematic is not to scale, nor does it represent the vertical temperature structure of the disk. INSET-left: Linearly-polarized intensity, scattered light image obtained with the Gemini Planet Imager (GPI) in the J-band (Laws et al 2020). The image is centered on FU Ori N within the black circle.…”

“…FU Ori is one of the best-studied YSOs due to its high magnitude and unique nature. Scattered light observations by Takami et al (2014) and Laws et al (2020) with Subaru and GPI re-spectively reveal a large spiral arm structure in the north-west of the disk extending around 200 au that has been attributed to a gravitational instability in the outer disk. Additionally, they reveal a stripe/shadow in the Northern disk and a diffuse outflow extending to the east, which is tentatively attributed to a jet in polar direction.…”

Reading between the lines

“…Stronger lines, which are likely to originate in the disk surface layers, tend to be more asymmetric and more variable, suggesting that the outer layers of the disk have a more complex structure than the midplane. The disks of HAeBe stars often have asymmetries in the outer layers at all radii (Benisty et al 2015;Laws et al 2020;Kluska et al 2020), so this is not unexpected. Hot spots could produce extra emission at low velocity, although we do not observe any rotational modulation in the narrow components.…”

SCExAO/CHARIS High-contrast Imaging of Spirals and Darkening Features in the HD 34700 A Protoplanetary Disk

“…ALMA continuum observation may help to investigate possible inner disk(s). Follow-up high-contrast observations are also useful to investigate time variation of the shadows and to constrain inner objects because previous observations reported (possible) changes of shadow features (on a timescale of years; Wisniewski et al 2008;Debes et al 2017;Stolker et al 2017;Uyama et al 2018;Rich et al 2019;Laws et al 2020). Assuming that an inner object at a radius of 0 2 (73 au, slightly interior to the physical inner working angle in our J-band result) casts a shadow on the ring (0 5) and that we can identify the time variation of the shadow if the shadow shifts by 30 mas (=J-band angular resolution in our observation), the inner object should move 12 mas (4.4 au).…”