Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars

Abstract

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 20 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 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 > 95% likelihood of Columba membership. The J0949 system shows > 95% 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 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 Paβ and Brγ 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 20 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?

Strong Hα emission and signs of accretion in a circumbinary planetary mass companion from MUSE

“…Murphy et al (2018) identified the 45 Myr old 0.1 M M5 WISE J0808-6443 as the host of a primordial disc, and these authors were recently joined by Lee et al (2020), who reported a likely transitional disc around another 0.1 M , M5 star, the 55 Myr old 2MASS J15460752-6258042. Silverberg et al (2020) identified another four, coining the term "Peter Pan discs" for these types of long-lived accretion discs that continue to be found around very low-mass stars. Perhaps even more interestingly, Boucher et al (2016) reported the detection of a disc around the L0, ∼14 M Jup BD and fellow THA member 2MASS J02265658-5327032.…”

The Gaia-ESO survey: a lithium depletion boundary age for NGC 2232

“…Resolving the age discrepancies in young clusters is crucial to correctly infer the properties and evolutionary processes of several strongly accreting stars identified at relatively late stages of their PMS, for example, TW Hydrae and Hen 3-600A (Muzerolle et al 2000, Ronco et al in preparation), dozens of accreting low-mass stars in Upper Scorpius (Manara et al 2020) and many more "classical" > 10 Myr old accretors identified in young stellar groups (Haisch et al 2001;Mamajek et al 2004;De Marchi et al 2013;Beccari et al 2017;Silverberg et al 2020).…”

Piloting Citizen Science Methods to Measure Perceptions of Carbon Footprint and Energy Content of Food

“…Citizen science invites members of the public to participate in scientific thinking and to collaboratively support researchers in their data collection around a set theme or experiment. For example, Zooniverse has been used to explore the properties of spiral galaxies (Hart et al, 2017) and young stars (Silverberg et al, 2020). Besides being a data collection mechanism, citizen science strives to engage broader audiences, to educate participants about the topics they are observing, and to experience the processes used in scientific investigations, thus providing impetus for possible changes in practice (van't Veer et al, 2017).…”