Post-doctorate fellowship in Astrophysics: “Nuclear Processes in accreting neutron stars”

23 Jan 2024
Job Information

Organisation/Company

Université Libre de Bruxelles (ULB)

Department

Faculté des Sciences

Research Field

Astronomy » Astrophysics
Physics » Neutron physics

Researcher Profile

Recognised Researcher (R2)

Country

Belgium

Application Deadline

2 Sep 2024 - 09:00 (Europe/Brussels)

Type of Contract

Temporary

Job Status

Full-time

Hours Per Week

38

Offer Starting Date

1 Feb 2024

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

The accretion of matter onto a neutron star (NS) induces various nuclear processes leading to
remarkable astrophysical phenomena. In low-mass X-ray binaries (LMXB), H-rich material is
transferred from a low-mass stellar companion to a NS and burns steadily producing a thick
He layer. Once the critical conditions for He ignition are reached, the overlying envelop is
converted into heavier nuclides. These thermonuclear explosions with total energies 1039-1040
erg are observed as X-ray bursts lasting a few tens of seconds and with a recurrence time of
hours to days. The nuclear products cannot be directly observed since no significant amount
of material is expected to be ejected. Less frequent are superbursts with energies ~1042 erg
lasting for a few hours with recurrence times of years, presumably triggered by the unstable C
burning. In most LMXB, accretion occurs sporadically. Soft X-ray transients (SXTs) exhibit
active periods of weeks to months separated by quiescent periods of years to decades. So-called
quasipersistent SXTs remain active for years to decades. As matter accumulates on the NS
surface, ashes of X-ray bursts are buried into deeper layers and further processed by electron
captures, neutron captures and emissions, and pycnonuclear fusions.
Depending on the duration of accretion episodes, the original crust can be partially or fully
replaced. In quasipersistent SXTs, the accretion can last long enough for the crust to be driven
out of thermal equilibrium with the core. The thermal relaxation of the crust has been
monitored in several systems over the past two decades. These observations provide unique
information on NS crust properties. Ongoing and future X-ray astronomical missions promise
a wealth of new discoveries with high-precision data, e.g., the extended Roentgen Survey with
an Imaging Telescope Array, NASA Imaging X-ray Polarimetry Explorer, the enhanced X-ray
Timing and Polarimetry mission (2027), and ESA/JAXA Advanced Telescope for High
ENergy Astrophysics (2035).
The present post-doctorate fellowship aims at providing a better understanding of the nuclear
processes occurring in accreting NSs and more precisely to model the full evolution of accreted
material, starting from nuclear processes taking place on the NS surface during X-ray bursts to
the burial of ashes deep inside the crust. The main objectives of the project are (i) to determine

the change of the NS crust composition due to X-ray bursts, (ii) to follow the long-term
evolution of the ashes as they sink inside the NS and calculate the detailed composition of fully
accreted NS crusts, their equation of state, the amount of heat deposited, and the location of
the heat sources, (iii) to use these results for simulating the thermal relaxation of the crust in
quasipersistent SXTs assessing the role of nuclear uncertainties and neutron superfluidity, and
(iv) to compare predictions with astrophysical observations.

The Post-doctorate position is available at the Institut d’Astronomie et d’Astrophysique (IAA)
of the Université Libre de Bruxelles (ULB) in Belgium to work with Nicolas Chamel, Stéphane
Goriely and Lionel Siess. The position is funded for 3 years. Screening of applications begins
immediately and continues until an outstanding candidate is selected. The position is to start
as soon as possible.
Profile requested:
• The candidate must have a PhD in physics, preferentially astrophysics or nuclear
physics awarded no later than 5 years before the start of the contract
• The candidate must have a good programming knowledge in Fortran and a strong
interest in numerical calculations;
• The applicant should have a good taste for interdisciplinary research, excellent
scientific writing and presenting skills and be able to work independently.
• Working in our international team requires capacity of team work and a good level of
English language.
Interested candidates should send their CV and request two referees to send their
recommendation letter directly to N. Chamel at [email protected]
Contact:
N. Chamel, S. Goriely & L. Siess
Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles
Campus de la Plaine CP 226
B-1050 Brussels, Belgium
Tel: +32 2 650 35 72
Email: [email protected]

 

Requirements

Research Field

Astronomy » Astrophysics

Education Level

PhD or equivalent

Skills/Qualifications

Profile requested:
• The candidate must have a PhD in physics, preferentially astrophysics or nuclear
physics awarded no later than 5 years before the start of the contract
• The candidate must have a good programming knowledge in Fortran and a strong
interest in numerical calculations;
• The applicant should have a good taste for interdisciplinary research, excellent
scientific writing and presenting skills and be able to work independently.
• Working in our international team requires capacity of team work and a good level of
English language.
 

Languages

ENGLISH

Level

Excellent

Additional Information
Eligibility criteria

The candidate must have a PhD in physics, preferentially astrophysics or nuclear
physics awarded no later than 5 years before the start of the contract
 

Work Location(s)

Number of offers available

1

Company/Institute

Université Libre de Bruxelles

Country

Belgium

Geofield

Where to apply

E-mail

[email protected]

Contact

City

Brussels

Website

http://www.astro.ulb.ac.be/pmwiki/IAA/HomePage

Street

50 avenue Franklin Roosevelt

Postal Code

1050

E-Mail

[email protected]

STATUS: EXPIRED