Seeing Through the Ring: Near-Infrared Photometry of V582 Mon (Kh 15d)

Abstract

We examine the light and color evolution of the T Tauri binary KH 15D through photometry obtained at wavelengths between 0.55 and 8.0 µm. The data were collected with ANDICAM on the 1.3 m SMARTS telescope at Cerro-Tololo Inter-American Observatory and with IRAC on the Spitzer Space Telescope. We show that the system's circumbinary ring, which acts as a screen that covers and uncovers different portions of the binary orbit as the ring precesses, has reached an orientation where the brighter component (star B) fully or nearly fully emerges during each orbital cycle. The fainter component (star A) remains fully occulted by the screen at all phases. The leading and trailing edges of the screen move across the sky at the same rate of ∼15 meters per second, consistent with expectation for a ring with a radius and width of ∼4 AU and a precession period of ∼6500 years. Light and color variations continue to indicate that the screen is sharp edged and opaque at VRIJH wavelengths. However, we find an increasing transparency of the ring edge at 2.2, 3.6, and 4.5 µm. Reddening seen at the beginning of the eclipse that occurred during the CSI 2264 campaign particularly suggests selective extinction by a population of large dust grains. Meanwhile, the gradual bluing observed while star B is setting is indicative of forward scattering effects at the edge of the ring. The SED of the system at its bright phase shows no evidence of infrared excess emission that can be attributed to radiation from the ring or other dust component out to 8 microns. Subject headings: stars: individual (KH15D) -stars: pre-main sequence -protoplanetary disks -Galaxy: open clusters and associations: individual (NGC 2264)

Spitzer Observations of Long-Term Infrared Variability Among Young Stellar Objects in Chamaeleon I

“…Wider binaries can experience periodic dimming as components of the binary pass behind a circumbinary disk, as is the case in KH 15D (e.g., Windemuth & Herbst 2014;Arulanantham et al 2016). The 131-day-period WL 4 system and the 93-day-period YLW 16A system (Plavchan et al 2013) show similar dimming behavior, suggesting a similar origin for their variability.…”

Double-peaked [O i] Profile: A Likely Signature of the Gaseous Ring around KH 15D

“…However, the circumbinary disk eluded detection. The system shows no infrared excess emission out to 8 µm (Arulanantham et al 2016), in line with the relatively large inner dust edge. In addition, the dust ring has not been detected at millimeter wavelengths with SMA or ALMA.…”

“…Chiang & Murray-Clay (2004) argued that the disk of KH 15D cannot extend beyond ∼5 au to maintain rigid precession and explain the long-term photometric variability of the system (but see Lodato & Facchini 2013 for the possibility of the disk extending to 5-10 au). Recently, Arulanantham et al (2016) confirmed the rigid precession of the ring and estimated a velocity (across the sky) of ∼15 m s −1 for the projected edge of the ring. Then, the precession rate of the ascending node of the ring can be estimated to be 0.…”

Alignment of a circumbinary disc around an eccentric binary with application to KH 15D

“…During the time between 2010 and 2012, both stars A and B were only detectable through scattered light. Currently, the brightness of the system has increased as star B's orbit has become uncovered from the the trailing edge of the precessing disc (Capelo et al 2012;Windemuth & Herbst 2014;Arulanantham et al 2016;Aronow et al 2018).…”

“…The obscuring material likely consists of solids that form a dust embedded layer within the gaseous disc. IR observations suggest that the solids consists of 1 to 50 micron size particles (Arulanantham et al 2016(Arulanantham et al , 2017. We define the full thickness of the obscuring layer as 2T.…”