25-269 Investigating the nature of Gamma-Ray Bursts with SVOM

25-269 Investigating the nature of Gamma-Ray Bursts with SVOM

• Astronomy, Astrophysics

Mission

Gamma-Ray Bursts (GRBs) are powerful sources of gamma-rays lasting from a fraction of a second to a few hundreds of seconds, appearing randomly over the entire sky. These elusive phenomena have been discovered in the late ’60s of the last century and have remained a mystery until the late ’90s, thanks to the observations of the Italian-Dutch satellite BeppoSAX, which have precisely located and associated them with extragalactic transient sources, hosted in galaxies that span up to the earliest phases of the Universe, when the first structures formed.

Nowadays, we know that GRBs are divided into two categories reflecting two different channels of production. The first one is related to „collapsars“, i.e., the final stages of very massive stars (30-50 times the mass of the Sun). Following the gravitational collapse of these stars, a black hole is created, and matter is accreted onto it. This matter is then ejected by powerful jets, and if these jets point towards the observer, we detect them as GRBs, followed by the associated afterglow (i.e., the emission following the GRB in the X-ray, optical, and radio bands lasting hours to days).

The second category of GRBs, the „mergers“, are believed to be associated with the merging of two compact objects (black holes or neutron stars), whose end product may be a black hole or a highly magnetized neutron star, dubbed a magnetar.

SVOM (Space-based astronomical Variable Object Monitor) is a space mission developed in cooperation by the CNES and the Chinese National Space Administration (CNSA). It was successfully launched on the 22nd of June 2024, and it carries on board four instruments, two developed by China and two developed by France under CNES responsibility. The payload is composed of two wide field-of-view instruments and two narrow field-of-view instruments. The wide field instruments are ECLAIRs (a coded mask telescope operating in the 4-150 keV energy range) and GRM (a non-imaging spectrometer operating in the 25 keV – 5 MeV energy range). The narrow field-of-view instruments are the MXT (0.2-10 keV) and the VT (400-1000 nm). The space-borne instruments are complemented on the ground by three dedicated robotic telescopes, two of them located in China and operating in the optical band, and one from a French-Mexican collaboration, located in Mexico, capable of observing the sky in the optical and near-infrared bands.

SVOM’s nominal lifetime is 3 years, with a possible 2-year extension. The PHD project deals with the use of SVOM data to study the characteristics of Gamma-Ray Bursts. The PHD student will be part of the scientific team of the MXT telescope. The Microchannel X-ray telescope is an innovative instrument based on the coupling of „Lobster Eye“ micropore X-ray optics to a state-of-the-art pnCCD with very good spectral capabilities. It has been developed by CNES, in close collaboration with CEA (Saclay), IJCLab (Orsay), MPE (Munich), and the University of Leicester.

The hosting laboratory is responsible for the MXT Instrument Center and has the lead scientific role in the person of the PHD director.

The successful PHD candidate will be asked to actively participate in the spectral and temporal analysis of the X-ray data collected by SVOM/MXT. These data shall then be compared to the broader data collected by the other SVOM instruments and international partners to provide a physical interpretation of the GRB phenomenon. In particular, aspects such as the modeling of the energy injection during the afterglow phase will be addressed to better constrain the nature of the compact object at the origin of the relativistic collimated matter flux with the goal of understanding whether we deal with black holes or magnetars in the case of merger events. Merger type events are of particular interest since they can also be detected through multi-messenger channels, such as gravitational waves. Binary neutron star mergers can be detected by the new generation ground-based interferometers (LIGO/Virgo/Kagra), and the sky regions corresponding to their alerts can rapidly be scanned with SVOM/MXT to look for X-ray counterparts, even in the absence of gamma-ray trigger signals.

The successful PHD candidate will also act as a „Burst Advocate“, taking part in regular shifts where they will be in charge of validating the SVOM alerts and coordinating the follow-up from the ground.

Application Process

For more information about the topics and the co-financial partner, contact Directeur de thèse –

Then, prepare a resume, a recent transcript, and a reference letter from your M2 supervisor/engineering school director and you will be ready to apply online before March 14th, 2025, Midnight Paris time!

Profil

Master’s degree in Physics, Astrophysics, or Astronomy.

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