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Accueil du site > Formation > Thèses - Stages de M2

Towards Precision Calibration of the AdvancedVirgo+ Gravitational Wave Detector for the observation periods O4 and O5.

Cette thèse peut être précédée par un stage de M2 au printemps 2022 pendant lequel l’étudiant pourra participer à l’étalonnage du détecteur Virgo avec le calibrateur optique existant pour la prise de données O4 et/ou commencer à tester et caractériser en laboratoire des dispositifs en vue d’améliorer les calibrateurs optiques pour les prises de données O4 et O5.

Un financement est disponible pour cette thèse.

PhD subject :

The Virgo gravitational wave detector, installed in Pisa, works on the principle of a laser interferometer with arms 3 km long. In August 2017, the first joint observation of gravitational waves, by the LIGO (United States) and Virgo (Italy) detectors, coming from a coalescence of neutron stars and a gamma burst, followed by that of an optical signal, opened a whole new chapter in multi-messenger astronomy. In addition to confirming the nature of short gamma- ray bursts, new types of measurements have been made, ranging from tests of general relativity to a new independent measurement of the Hubble constant, with an accuracy of around 15%. After improving the detectors, another joint observation period in 2019/2020 brought the number of compact binary system coalescences detected (mostly black holes) to around 70. The next data acquisition, called O4, will start in the fall of 2022 and should allow this number of detected events to be multiplied by 3. This exponential progression should continue during the next data taking. With more and more detections to come, the precision of the detector calibration and the precision of the reconstruction of the gravitational wave signal will have to be better and better controlled. In 2019/2020, the gravitational wave signal from Virgo was reconstructed online with an uncertainty of around 5%. As the sensitivity of the detectors improves, the number of sources detected will increase, and some sources will be observed with a signal to noise ratio of a few dozen. It is therefore necessary to reduce the uncertainties of the calibration and reconstruction of the gravitational wave signal at the percent level so as not to limit the studies of fundamental physics, astrophysics and cosmology. In order to correctly reconstruct the astrophysical parameters (direction, distance, masses, spins, ...) of the sources of gravitational waves detected, it is important to understand the way in which these uncertainties on the reconstructed signal influence the precision of the estimated parameters, especially for events detected online. The LAPP Virgo team is developing a calibration technique, the photon calibrator, based on the radiation pressure of an auxiliary laser to displace a hanging mirror by a known amount. This technique is currently the reference method for calibrating LIGO and Virgo detectors, and an intercalibration procedure for the various detectors in the network is being implemented. One of the objectives of the proposed thesis is to improve the precision of this technique below one percent, to extend its useful frequency band to high frequencies, as well as to actively participate in the intercalibration of the various LIGO, Virgo and KAGRA (Japan) detectors It will also be very useful to inter-calibrate the optical calibrator with a Newtonian calibrator, a new calibration technique developed by the Strasbourg team based on a variable gravitational field. Another aspect of this thesis work would consist in reducing the time required to provide the gravitational wave signal h (t) to on-line analyzes, without losing too much precision, in order to allow pre-alerts on the detections of coalescence of binaries of neutron stars.

Funding is available for this thesis.

Summary of the work required during the M2 internship :

This thesis can be preceded by an M2 internship in spring 2022 during which the student can participate in the calibration of the Virgo detector with the existing photon calibrator for taking O4 data and /or start testing and characterizing devices in the laboratory. to improve photon calibrators for O4 and O5 data.

o Niveau : Master 2

o Supervisor : Loïc Rolland

o Phone : 04 50 55 18

o e-mail :

More details :