Infrared H2 Emission Nebulousity

Associated with KH 15D

Tokunaga, A. T., Dahm, S., Gaessler, W., Hayano, Y., Hayashi, M., Iye, M., Kanzawa, T., Kobayashi, N., Kamata, Y., Minowa, Y.,

Nedachi, K., Oya, S., Pyo, T., Saint-Jacques, D., Terada, H., Takami, H., Takato, N.,

2004, Astrophys. J., 601, L91.

KH 15D is a peculiar variable star in NGC 2264

Discovered by Kearns & Herbst, 1998, ApJ, 116, 261

More info: http://www.astro.wesleyan.edu/research/kh15d/

Basic facts:

Position RA, Dec: 06:41, +09:28

V, J, H, K 16.1, 13.7, 13.0, 12.8 mag

Spectral Type K6-K7

Distance 760 pc

Luminosity 0.5 L_sun

Age 2-4 Myr

Light curve, Hamilton et al. 2005, astro-ph/0507578

Note period of 48.37 days

95-96

97-98

99-00

01-02

03-04

•Period 48.4 days, I~14.5 to ~18 mag

•No eclipses from 1913 to 1950

•Apparent phase shift:

1967-1970

2001-2002

Chiang & Murray-Clay (2004, ApJ, 607, 913) and Winn et al. (2004, ApJ, 603, L45) found that all of the eclipse data can be explained as the gradual occultation of a binary system. The edge of the ring is very sharp-- in fact the light curve suggests that it is like a knife edge. The geometry of the system is shown in the next slide.

The sharp edge of the ring strongly suggests that there is a planetary body confining the edge of the ring.

The inner edge of the ring is about 1 AU and the outer edge is about 5 AU. The binary itself has a semi-major axis of about0.2 AU.

From: Chiang, E. & Murray-Clay, R. 2004, ApJ, 607, 913

Edge of ring

Imaging by Subaru

Goal: Looking for nebulousity.

Used IRCS and AO on Subaru.

Tokunaga et al. 2004, ApJ, 601, L91

The imaging was first done in K-band to search for nebulousity. The jet-like morphology was unexpected. To make sure it is an emission feature, narrow-band imaging in H2 was obtained.

Narrow-band imaging with the H2 filter and the K-continuum proves that the emission arises from H2. Spectroscopy by Deming et al. (2004, ApJ, 601, L87) confirms this. The H2 emission is enhanced at the position of KH 15D, implying a physical association.

White lines show outline of possible outflow cavity.

H2 image from the UH 2.2-m. This image shows that the H2 emission is localized to KH 15D; it is not part of a larger structure.

KH 15D

Tokunaga et al. 2004, ApJ, 601, L91

Major Questions

• What can we learn about the outflow process?

• Further observations of the light curve will constrain models; in particular is there a planet that is defining the outer radius of the ring? Ring edge is very sharp.

• How stable is the ring?

• Could rings be as common as planets?

• What is this telling us about planet formation?