Discovery of a Thorne-Żytkow Object Candidate in the Small Magellanic Cloud
Emily Levesque University of Washington
Philip Massey (Lowell Observatory), Nidia Morrell (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 star: a neutron star “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 accretion
• 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 main sequence, 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 supernova 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 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 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)