OzGrav

  • Home
  • About
    • Vision & Mission
    • Join OzGrav
    • Mental Health and Wellbeing
    • Getting started in OzGrav
    • Funding Opportunities
    • Diversity and Inclusion
    • Code of Conduct
    • OzGrav Mentoring Program
    • Nodes & Partners
    • Facilities & Capabilities
    • Reports >
      • Annual Reports
      • Industry Success Stories
      • Strategic Plan
    • Member resources
  • Our People
    • Chief Investigators
    • Partner Investigators
    • Associate Investigators
    • Postdocs and Students >
      • Faces of OzGrav
    • Professional & Outreach staff
    • Governance Advisory Committee
    • Scientific Advisory Committee
    • Executive Committee
    • Equity & Diversity Committee
    • Early Career Researcher Committee
    • Professional Development Committee
    • Research Translation Committee
    • OzGrav Alumni
  • Research Themes
    • Instrumentation
    • Data/Astro
    • How to write a research brief
  • Education and Outreach
  • Events
    • OzFink workshop 2023
    • 2022 OzGrav ECR Workshop and Annual Retreat
    • Upcoming and Past Events
  • News/Media
    • News
    • Newsletter
    • Binary Neutron Star Discovery
  • Contact Us
  • Home
  • About
    • Vision & Mission
    • Join OzGrav
    • Mental Health and Wellbeing
    • Getting started in OzGrav
    • Funding Opportunities
    • Diversity and Inclusion
    • Code of Conduct
    • OzGrav Mentoring Program
    • Nodes & Partners
    • Facilities & Capabilities
    • Reports >
      • Annual Reports
      • Industry Success Stories
      • Strategic Plan
    • Member resources
  • Our People
    • Chief Investigators
    • Partner Investigators
    • Associate Investigators
    • Postdocs and Students >
      • Faces of OzGrav
    • Professional & Outreach staff
    • Governance Advisory Committee
    • Scientific Advisory Committee
    • Executive Committee
    • Equity & Diversity Committee
    • Early Career Researcher Committee
    • Professional Development Committee
    • Research Translation Committee
    • OzGrav Alumni
  • Research Themes
    • Instrumentation
    • Data/Astro
    • How to write a research brief
  • Education and Outreach
  • Events
    • OzFink workshop 2023
    • 2022 OzGrav ECR Workshop and Annual Retreat
    • Upcoming and Past Events
  • News/Media
    • News
    • Newsletter
    • Binary Neutron Star Discovery
  • Contact Us

RESEARCH HIGHLIGHT: EXPLORING COMMON ENVELOPE OUTCOMES WITH RESPONSES OF STRIPPED STARS

11/10/2021

0 Comments

 
PictureIllustration of binary neutron stars - Carl Knox, OzGrav-Swinburne University
Binary neutron stars have been detected in the Milky Way as millisecond pulsars and twice outside the galaxy via gravitational-wave emission. Most of them have orbital periods of less than a day—a contrasting difference to their progenitors: massive stellar binaries that have hundreds or thousands of days orbital periods. In the last several decades, there has been much debate about explaining how massive binaries transition to double compact objects. To date, one of the strong contenders to explain this transition is the highly-complex stage of binary stellar evolution known as the common-envelope phase.
 
The common-envelope phase is a particular outcome of a mass transfer episode. It begins with the Roche-lobe overflow of (at least) one of the stars, and it’s prompted by a dynamical instability. In a simple version, the stellar envelope of the mass-transferring star—the donor—bloats and engulfs the whole binary, creating a new system comprised of an inner compact binary, and a shared “common” envelope. The interaction of the inner binary with the common envelope results in drag, and the dissipated gravitational energy is transferred onto the common envelope, which can lead to its ejection. A successful ejection suggests that a compact binary can form. But what does a “successful ejection” mean?
 
To explore the common-envelope phase with three-dimensional hydrodynamical models, we attempted to address the likely outcomes of common-envelope evolution by considering the response of a one-dimensional stellar model to envelope removal. In a recent study, we focussed on the common-envelope phase scenario of a donor star with a neutron star companion. We emulated the common-envelope phase by removing the envelope of the donor star, either partially or completely. After the star was stripped, we followed its radial evolution. The most extreme scenarios resulted as expected: If you remove all the envelope, the stripped star remains compact. Alternatively, if you leave most of the envelope, the stripped star subsequently expands a lot. The question is: what happens in between the extreme cases?
 
Our research shows that when most of the envelope, but not all of it, is removed, the star experiences a short phase of marginal contraction (<100 years), but overall, the star remains compact during the next 1000 years. This suggests that a star doesn’t needs to be stripped all the way to the core to avoid an imminent stellar merger. Moreover, the amount of energy needed to partially strip the envelope is less than the one needed to fully remove it. Finally, it’s reassuring that our results show a strong correlation to variations in donor mass and composition.
 
This research is a step forward in the understanding of the common envelope phase and the formation of double neutron star binaries. Our results imply that a star can be stripped without experiencing Roche lobe overflow immediately after the common envelope, a likely condition for a successful envelope ejection. It also suggests that stripped stars retain a few solar masses of peculiar, hydrogen-poor material in their surface. While this amount of hydrogen is not excessive, it might be observable in the spectra of a star and can play a role at the end of its life when it explodes into a supernova. While the full understanding of the common-envelope phase remains elusive, we are connecting the dots of the evolution and fate of systems that have experienced a common-envelope event.
 
Written by OzGrav research Alejandro Vigna-Gómez from the Niels Bohr Institute (University of Copenhagen)


0 Comments



Leave a Reply.

         


    OzGrav News


    Archives

    December 2022
    November 2022
    September 2022
    July 2022
    June 2022
    May 2022
    April 2022
    March 2022
    February 2022
    January 2022
    December 2021
    November 2021
    October 2021
    September 2021
    August 2021
    July 2021
    June 2021
    May 2021
    April 2021
    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    August 2019
    July 2019
    June 2019
    April 2019
    March 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    April 2018
    March 2018
    February 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    December 2016
    September 2016
    June 2016
    February 2016

    Categories

    All
    Event
    Media

      Keep up to date with ozgrav news and events

    Subscribe to Newsletter

    RSS Feed

Picture
Picture
Picture
Picture
Picture
Picture
Picture
Picture
We acknowledge and pay respects to the Elders and Traditional Owners of the land on which our six Australian nodes stand

​© 2022   The ARC Centre of Excellence for Gravitational  Wave Discovery (OzGrav)
Banner images: An artist's impression of gravitational waves generated by binary neutron stars.  Credits: R. Hurt/Caltech-JPL
Picture