PDS 144: The First Confirmed Herbig Ae - Herbig Ae Wide Binary

TL;DR

This paper confirms PDS 144 as the first Herbig Ae - Herbig Ae wide binary, revealing a disk around the northern star and analyzing the system's dynamics, including proper motion, inclination, and disk misalignment.

Contribution

It provides the first confirmation of a Herbig Ae - Herbig Ae wide binary system and details the disks' orientations and misalignment, using multi-epoch HST imagery and radial velocity data.

Findings

PDS 144 N has an edge-on disk.

PDS 144 N and S are physically associated and comoving.

Disks are misaligned by approximately 25 degrees.

Abstract

PDS 144 is a pair of Herbig Ae stars that are separated by 5.35" on the sky. It has previously been shown to have an A2Ve Herbig Ae star viewed at 83\circ inclination as its northern member and an A5Ve Herbig Ae star as its southern member. Direct imagery revealed a disk occulting PDS 144 N - the first edge-on disk observed around a Herbig Ae star. The lack of an obvious disk in direct imagery suggested PDS 144 S might be viewed face-on or not physically associated with PDS 144 N. Multi-epoch Hubble Space Telescope imagery of PDS 144 with a 5 year baseline demonstrates PDS 144 N & S are comoving and have a common proper motion with TYC 6782-878-1. TYC 6782-878-1 has previously been identified as a member of Upper Sco sub-association A at d = 145 \pm 2 pc with an age of 5-10 Myr. Ground-based imagery reveals jets and a string of Herbig-Haro knots extending 13' (possibly further) which are aligned to within 7\circ \pm 6\circ on the sky. By combining proper motion data and the absence of a dark mid-plane with radial velocity data, we measure the inclination of PDS 144 S to be i = 73\circ \pm 7\circ. The radial velocity of the jets from PDS 144 N & S indicates they, and therefore their disks, are misaligned by 25\circ \pm 9\circ. This degree of misalignment is similar to that seen in T Tauri wide binaries.