Discovery of a Thorne-Żytkow Object Candidate in the

Emily Levesque University of Washington

Philip Massey (Lowell Observatory), (LCO), Anna Żytkow (Cambridge)

Trevor Dorn-Wallenstein, Kolby Weisenburger (UW), Je"rey Jennings (CU Boulder)

Arizona State University Apr 27, 2016 Thorne-Żytkow Objects (TŻOs) are a theoretical class of : a “core” surrounded by a large di"use envelope

• Thorne & Żytkow (1977) predict supergiant TŻOs (Mc =

1.0M⦿, Mt ≥ 11.5M⦿)

• Powered by a combination of thermonuclear reactions and gravitational

• Represent a completely new model for stable stellar interiors.

There has never been a confirmed observation of a TŻO. Formation of TŻOs 1. Engulfing - an OB + NS HMXB; the OB companion leaves the , evolves into an RSG, expands, and engulfs the NS companion (Taam et al. 1978)

2. Collision - a massive binary system; one member collapses into a NS, and kick velocity propels it into the massive companion (Leonard et al. 1994) TŻOs are...

cool and luminous, lying at or beyond the Hayashi limit for massive (Thorne & Żtykow 1977)

strongly -losing as a result (van Paradijs et al. 1995)

potentially more common at low Z (Linden et al. 2010)

TŻOs are...

The cool periodic and luminous, table… lying at or beyond the Hayashi limit for massive stars (Thorne & Żtykow 1977)

strongly mass-losing as a result (van Paradijs et al. 1995) X I - neutral atom potentially moreX IIcommon - singly-ionized atom at low Z (Linden et al. 2010) X III - double-ionized atom

metallicity

^ TŻOs are... astronomers’

The cool periodic and luminous, table… lying at or beyond the Hayashi limit forH massive stars (Thorne & He Żtykow 1977)

strongly mass-losing as a result (van Paradijs et al. 1995) X I - neutral atom “metals” (Z) potentially moreX IIcommon - singly-ionized atom at low Z (Linden et al. 2010) X III - double-ionized atom

metallicity TŻOs are...almost indistinguishable from RSGs...

cool and luminous, lying at or beyond the Hayashi limit for massive stars (Thorne & Żtykow 1977)

strongly mass-losing as a result (van Paradijs et al. 1995) ? potentially more common at low Z (Linden et al. 2010)

metallicity (anything beyond H and He) TŻOs are...almost indistinguishable from RSGs...

cool and luminous, lying at or beyond the Hayashi limit for massive stars (Thorne & RSG surface Żtykow 1977)

strongly mass-losing as a result (van Paradijs et al. 1995)

potentially more common at low Z (Linden et al. 2010)

He burning core TŻOs are...almost indistinguishable from RSGs...

cool and luminous, lying at Mo Ru Zr Li Y Sr Rb or beyond the Hayashi limit for massive stars (Thorne & Żtykow 1977) TŻO surface irp-process Wallace & ! strongly mass-losing as a Woosley (1981) result (van Paradijs et al. Cannon (1993) 1995) Be-transport 7Be + e- ! Cameron (1955) potentially more common 7Li + v Podsiadlowski at low Z (Linden et al. 2010) (1995) ! unique chemical profile (Biehle 1994) p+ + 7Li ! p+ p+ + + p 4 p+ p + 2 He + + p NS core p p TŻOs are...almost indistinguishable from RSGs...

cool and luminous,Red supergiant lying at Mospectrum Ru Zr Li Y Sr Rb or beyond the Hayashi limit for massive stars (Thorne & TŻO surface irp-process Żtykow 1977) Biehle (1994) Wallace & ! strongly mass-losing as a Woosley (1981) result (van Paradijs et al. Cannon (1993)