Job Information
- Organisation/Company
- Université Libre de Bruxelles (ULB)
- Department
- Faculté des Sciences
- Research Field
- Astronomy » AstrophysicsPhysics » Neutron physics
- Researcher Profile
- Recognised Researcher (R2)
- Country
- Belgium
- Application Deadline
- Type of Contract
- Temporary
- Job Status
- Full-time
- Hours Per Week
- 38
- Offer Starting Date
- 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 Nicolas.Chamel@ulb.be
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: Nicolas.Chamel@ulb.be
Requirements
- Research Field
- Astronomy » Astrophysics
- Education Level
- PhD or equivalent
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
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
- nicolas.chamel@ulb.be
Contact
- City
- Brussels
- Website
- Street
- 50 avenue Franklin Roosevelt
- Postal Code
- 1050
- nicolas.chamel@ulb.be