Letters of Intent received in 2016

LoI 2018-1969
High-mass X-ray binaries at the cross-roads of astrophysics

Date:	20 August 2018 to 31 August 2018
Category:	Non-GA Symposium
Location:	Vienna, Austria
Contact:	Lidia Oskinova (lida@astro.physik.uni-potsdam.de)
Coordinating division:	Division D High Energy Phenomena and Fundamental Physics
Other divisions:	Division G Stars and Stellar Physics
Co-Chairs of SOC:	Enrico Bozzo (ISDC)
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Co-Chairs of LOC:	()
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Topics

1. Massive stars and mass-loss;
2. Massive binary evolution;
3. End points of massive star lives;
4. HMXBs formation and populations;
5. Properties of HMXBs;
6. Massive donor stars and accretions;
7. Accretion physics;
8. Properties of compact objects in HMXBs;
9. From HMXBs to double degenerates;
10. GW constraints to massive binary physics

 

Rationale

Dear colleagues,

Recent observational and theoretical advances led to an extremely rapid progress in the research of high-mass X-ray binaries (HMXBs). Consisting of a young massive donor star
and an accreting degenerate object (a neutron star or a black hole), these objects provide unique astrophysical laboratories for studies of massive stars and compact objects. Moreover, HMXBs are our cosmic neighbors that allow deep insights into the physics of accretion and on matter under extreme conditions. To fully exploit scientific potential of HMXBs, a synergistic approach comprising the physics of stars, compact objects, and their interactions, must be developed.

Since their discovery 50 years ago, HMXBs were traditionally investigated by rather different communities. While X-ray astronomers are deeply involved in studies of compact objects and accretion processes, the stellar astronomers are mainly interested in the donor star properties. Moreover, the different types of HMXBs - BeXRBs, supergiant HMXBs, and ULXs - are usually discussed during separate specialized meetings. Also, there is an urgent need to improve the links and scientific exchanges
between the massive star and HMXBs communities.

We intend to propose an IAU symposium that will provide a consistent view on the various types of HMXBs and place these objects into a general context of stellar evolution. The feedback from HMXBs on galaxies and their evolution, including
early epochs in the Universe, will also be considered. This goal can only be achieved when experts in multiwavelength and multimessenger observations get together with the scientists working on theoretical aspects of massive stars, compact objects, and accretion.

The prime goal of the proposed IAU symposium is to develop a unified view of HMXBs that incorporates stellar, X-ray, and gravitational wave astrophysics.The proposed IAU Symposium will provide a scope for a productive exchange of
knowledge and ideas, consolidate the communities, bring a much needed clarity in our general understanding of HMXBs, and pave new research avenues.

The proposed meeting should cover the relevant astrophysical subjects:

* Massive stars: rotation, magnetic fields, winds and mass loss rates in dependence on
metallicity

* Massive binary evolution and the populations of massive binary stars in galaxies

* End points of massive star lives (SNe, GRBs, and other channels) and the post-collapse binary properties

* HMXBs formation and populations in dependence on metallicity: confronting theory and observations

* Properties of HMXBs: orbits, component masses, luminosities, environment

* Massive donor stars and accretion onto compact objects: stellar winds and X-ray irradiation

* Accretion physics (including in the presence of strong magnetic fields)

* Properties of compact objects in HMXBs: masses, spins, neutron star magnetic fields, binary parameters

* From HMXBs to double degenerates: formation channels and
evolution

* Astrophysical implications of GW observations: constraints to massive binary physics and evolution

Given its interdisciplinary nature, the framework of the IAU General Assembly is very well suited for the suggested Symposium. We strongly believe that the time is now
ripe for obtaining a broad picture of HMXBs and 2018 is the optimum time to held the meeting.

The revolutionary detection of gravitational waves from merging stellar-mass black holes places HMXBs in the focus of current astrophysical research as the key transitional stage between young massive stars and double degenerate binaries. At present, there is a burst of theoretical work on the evolution of massive binary stars towards double degenerate mergers. Besides the standard population synthesis models that have predicted the gravitational wave detection rates, new models and scenarios are being actively discussed and investigated. All these models require robust knowledge of massive star evolution, that is largely governed by prodigious stellar loss of mass.

By 2018 the gravitational wave detectors will provide robust statistics on the populations of close double degenerate binaries, as well as on their physical properties. At the same time, our knowledge of HMXBs will be significantly improved due to the new advances in X-ray and high-energy observations (e.g.
the new X-ray surveyor eROSITA is scheduled for launch in 2017). Moreover, X-ray polarimetry will likely become a new tool in astrophysics research.

We already built up a working group (see below) that will coordinate the preparation of the proposal and the organization of the SOC. The working group will ensure that the scientific, geographical and gender diversity balance is observed. This aim for diversity and balance will be carried throughout the meeting, to ensure a fair representations among invited speakers and session chairs. We will also pay particular attention to giving a chance for early career astronomers to present their work at this significant large-scale meeting. Importantly, we foresee that the proposed IAU Symposium will help to improve communication and consolidation of the communities and lead to new initiatives in organization of new meetings and working groups.

We received strong support from Division D, which will coordinate the meeting. We also received the endorsement of Division G. The relevant commissions will be involved
in the proposal preparation.

Working group:
John Blondin (US), Enrico Bozzo (Swiss), Tomek Bulik (Poland), Malcolm Coe (UK),
Doug Gies (US), Lidia Oskinova (Germany), Konstantin Postnov (Russia),
Pablo Reig (Greece), Lara Sidoli (Italy), John Tomsick (US), Jose Miguel Torrejon (Spain)