"Ringdown overtones in black hole binary mergers"

Roberto Cotesta , John Hopkins University
[Host: Kent Yagi]

The gravitational-wave signal emitted by the black-hole remnant resulting from a binary merger such as GW190514 consists in a superposition of damped sinu- soids known as quasinormal modes. Besides the “fundamental" mode (the one with the longest damping time), it is important to detect the so-called “over- tones" (modes with shorter damping time), because a measurement of their frequencies could allow us to identify the remnant as a Kerr black hole. We discuss theoretical and observational issues in the analysis of ringdown over- tones. We present theoretical arguments showing that the spacetime is not well described as a linearly perturbed black hole close to the peak of the waveform amplitude. Then we analyze GW150914 post-merger data to understand if recent ringdown overtone detection claims are robust. We find no evidence in favor of an overtone in the data after the waveform peak. Around the peak, the log-Bayes factor does not indicate the presence of an overtone, while the support for a non-zero amplitude is sensitive to changes in the starting time much smaller than the overtone damping time. This suggests that claims of an overtone detection are noise-dominated. We perform GW150914-like injections in neighboring segments of the real detector noise, and we show that noise can indeed induce artificial evidence for an overtone.


Gravity Seminar
Monday, November 21, 2022
1:30 PM
Physics, Room 313

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"Building and Characterizing an Atom Interferometer Gyroscope"

Marybeth Beydler
[Host: Prof. Peter Schauss]

Inertial Navigation Systems (INS) are alternatives to GPS that operate using linear accelerometers and gyroscopes to calculate the user’s position, orientation, and velocity using no external reference. Optical Sagnac gyroscopes are part of modern day INS and are limited by their ability to measure small rotations as they need a very large enclosed area. The Bragg Interferometer Gyroscope in a Time Orbiting Potential Trap (BIGTOP) is a rotation detector using a Bose-Einstein Condensate (BEC) to execute two Sagnac interferometers in a magnetic trap. BIGTOP is an improvement upon a previous iteration of a dual Sagnac interferometer which demonstrated rotation sensing. We have achieved atom interferometry with BIGTOP and reached a Sagnac area of 8 mm2 using multiple orbits, an improvement by a factor of 16. Additionally, we have taken our first large dataset over the course of 24 hours, which can be used to analyze the stability of our system. In tandem with BIGTOP, we have also worked to characterize and operate a compact atom chip interferometer system built by Cold Quanta (CQsystem). We report BIGTOP results, progress with the CQ system, and future work.

Atomic Physics Seminar
Monday, November 21, 2022
4:00 PM
Chemistry Building , Room 206

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