9 research outputs found
Follow-up Imaging of Disk Candidates from the Disk Detective Citizen Science Project: New Discoveries and False Positives in WISE Circumstellar Disk Surveys
The Disk Detective citizen science project aims to find new stars with excess 22 m emission from circumstellar dust in the All WISE data release from the Wide-field Infrared Survey Explorer. We evaluated 261 Disk Detective objects of interest with imaging with the Robo-AO adaptive optics instrument on the 1.5 m telescope at Palomar Observatory and with RetroCam on the 2.5 m du Pont Telescope at Las Campanas Observatory to search for background objects at 0 1512 separations from each target. Our analysis of these data leads us to reject 7% of targets. Combining this result with statistics from our online image classification efforts implies that at most7.9%0.2% of All WISE-selected infrared excesses are good disk candidates. Applying our false-positive rates to other surveys, we find that the infrared excess searches of McDonald et al. and Marton et al. all have false-positiverates >70%. Moreover, we find that all 13 disk candidates in Theissen & West with W4 signal-to-noise ratio >3are false positives. We present 244 disk candidates that have survived vetting by follow-up imaging. Of these,213 are newly identified disk systems. Twelve of these are candidate members of comoving pairs based on Gaia astrometry, supporting the hypothesis that warm dust is associated with binary systems. We also note the discovery of 22 m excess around two known members of the ScorpiusCentaurus association, and we identifyknown disk host WISEA J164540.79-310226.6 as a likely Sco-Cen member. Thirty of these disk candidates arecloser than 125 pc (including 26 debris disks), making them good targets for both direct-imaging exoplanetsearches
Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars
WISEA J080822.18-644357.3, an M star in the Carina association, exhibits
extreme infrared excess and accretion activity at an age greater than the
expected accretion disk lifetime. We consider J0808 as the prototypical example
of a class of M star accretion disks at ages Myr, which we call
``Peter Pan'' disks, since they apparently refuse to grow up. We present four
new Peter Pan disk candidates identified via the Disk Detective citizen science
project, coupled with \textit{Gaia} astrometry. We find that WISEA
J044634.16-262756.1 and WISEA J094900.65-713803.1 both exhibit significant
infrared excess after accounting for nearby stars within the 2MASS beams. The
J0446 system has likelihood of Columba membership. The J0949 system
shows likelihood of Carina membership. We present new GMOS optical
spectra of all four objects, showing possible accretion signatures on all four
stars. We present ground-based and \textit{TESS} lightcurves of J0808 and 2MASS
J0501-4337, including a large flare and aperiodic dipping activity on J0808,
and strong periodicity on J0501. We find Pa and Br emission
indicating ongoing accretion in near-IR spectroscopy of J0808. Using observed
characteristics of these systems, we discuss mechanisms that lead to accretion
disks at ages Myr, and find that these objects most plausibly
represent long-lived CO-poor primordial disks, or ``hybrid'' disks, exhibiting
both debris- and primordial-disk features. The question remains: why have
gas-rich disks persisted so long around these particular stars?Comment: 25 pages, 17 figures. Accepted for publication in the Astrophysical
Journa