Are merging black holes born from stellar collapse or previous mergers?

Monday, June 26, 2017

The paper Are merging black holes born from stellar collapse or previous mergers? by Davide Gerosa and Emanuele Berti was published today in Physical Review D and selected as an Editors’ Suggestion. Ars Technica has a write-up on our paper.
From the abstract:

Advanced LIGO detectors at Hanford and Livingston made two confirmed and one marginal detection of binary black holes during their first observing run. The first event, GW150914, was from the merger of two black holes much heavier that those whose masses have been estimated so far, indicating a formation scenario that might differ from “ordinary” stellar evolution. One possibility is that these heavy black holes resulted from a previous merger. When the progenitors of a black hole binary merger result from previous mergers, they should (on average) merge later, be more massive, and have spin magnitudes clustered around a dimensionless spin ∼0.7. Here we ask the following question: can gravitational-wave observations determine whether merging black holes were born from the collapse of massive stars (“first generation”), rather than being the end product of earlier mergers (“second generation”)? We construct simple, observationally motivated populations of black hole binaries, and we use Bayesian model selection to show that measurements of the masses, luminosity distance (or redshift), and “effective spin” of black hole binaries can indeed distinguish between these different formation scenarios.

Postdoctoral Position in Gravitational Wave Astronomy at the University of Mississippi

Sunday, June 18, 2017

The University of Mississippi invites applications for a postdoctoral position in the area of Gravitational Wave Astronomy. The position is for one year, renewable for up to three years. The applicant must have (or be close to completing) a Ph.D. in Physics or Astrophysics, with a good track record in one or more of the following research areas: gravitational-wave source modeling and parameter estimation, the astrophysics of compact binaries, Bayesian model selection, black hole perturbation theory, post-Newtonian theory, numerical relativity and modified gravity.

The Gravitational and High-Energy Theory Group at the University of Mississippi is active in various areas of theoretical and experimental gravity, and is part of the LIGO collaboration. Permanent faculty in the group include Emanuele Berti, Luca Bombelli, Marco Cavaglia and Katherine Dooley, as well as postdocs and several graduate students.

More information on the gravity group in Mississippi is available at the following URL:

The postdoctoral scholar funded by this position will work with Professor Emanuele Berti ( and several Ph.D. students. The research will be carried out in close collaboration with the group led by Bangalore Sathyaprakash, Elsbach Professor of Physics and Professor of Astronomy and Astrophysics at Penn State University. The successful applicant is expected to engage in a collaborative research program including several institutions (Lisbon, Cambridge, Rome, Paris and Aveiro in Europe, Perimeter Institute in Canada, and Osaka University in Japan) through the “Strong Gravity and High Energy Physics” Marie Sklodowska-Curie Research and Innovation Staff Exchange (RISE) Action, funded by the EU Horizon 2020 program H2020-MSCA-RISE-2015.

A curriculum vitae (including a list of publications and a statement of research interests) should be sent to the following e-mail address:

Please use the subject “Gravitational wave postdoc”. Applicants must also arrange to have at least three recommendation letters to be sent to the same email address.

Applications should be submitted as soon as possible.
The position will be open until filled.

Davide Gerosa wins the 2016 Stefano Braccini Thesis Prize

Every year the Gravitational Wave International Committee (GWIC) awards two thesis prizes: the GWIC Thesis Prize and the Stefano Braccini Thesis Prize.

Our collaborator (and former Master student at Ole Miss) Davide Gerosa won the 2016 Stefano Braccini Thesis Prize for theoretical work on gravitational wave sources. Davide, who is now an Einstein Fellow at the California Institute of Technology, defended his Ph.D. thesis (Source modelling at the dawn of gravitational-wave astronomy, available for download here) at the University of Cambridge. His advisor was Ulrich Sperhake (also an Adjunct Professor at the University of Mississippi).

From the announcement:

GWIC is pleased to announce that the selection committee for the GWIC Thesis Prize and the Stefano Braccini Thesis Prize has reached a decision. This year, there was a total of 9 theses nominated, from 5 different countries.

This is the fourth year that a single committee selects the winners of the two thesis prizes. The selection committee was instructed to select the two best theses based on 1) originality and creativity of the research, 2) importance to the field of gravitational waves and gravitational wave detection, broadly interpreted, and 3) clarity of presentation in the thesis. To distinguish between the two prizes, the GWIC Thesis Prize emphasizes the impact on the field of gravitational waves, and the Stefano Braccini Thesis Prize emphasizes the novelty and innovation of the research.

The 2016 GWIC Thesis Prize is awarded to Eric Oelker for his thesis “Squeezed States for Advanced Gravitational Wave Detectors”. Dr. Oelker received his Ph.D. from the Massachusetts Institute of Technology and was nominated by his adviser, Prof. Nergis Mavalvala. His thesis describes a beautiful experiment demonstrating frequency-dependent squeezed states suitable for Advanced LIGO. This is a key element in all the designs for detectors with sensitivity beyond the second generation baselines.

The 2016 Stefano Braccini Thesis Prize is awarded to Davide Gerosa for his thesis “Source modelling at the dawn of gravitational-wave astronomy”. Dr. Gerosa received his Ph.D. from the University of Cambridge and was nominated by his adviser, Prof. Ulrich Sperhake. Dr. Gerosa’s thesis includes a wide variety of topics relevant to gravitational waves, as well as other topics in astrophysics: astrophysical explorations of accretion disks, analytically challenging work in mathematical relativity and post-Newtonian theory, and numerical relativity coding of supernova core-collapse in relativity and modified gravity.

Congratulations, Davide!

LIGO is awarded the 2017 Princess of Asturias Award by the King of Spain

Saturday, June 17, 2017

From His Majesty the King of Spain

On behalf of Our Daughter Leonor, Princess of Asturias and honorary president of the foundation that bears her name, the Queen and I have the pleasure of extending to you our sincerest congratulations for the 2017 Princess of Asturias Award for Technical and Scientific Research that has been jointly granted to the Ligo Scientific Collaboration, together with Rainer Weiss, Kip S. Thorne and Barry C. Barish, for the detection of gravitational waves, one of the most outstanding discoveries in physics, which has opened up a new era in our study, knowledge and comprehension of the universe.

Most affectionately,

Felipe R.

LIGO detects a third pair of merging black holes

Thursday, June 1, 2017

Scientists from the Laser Interferometer Gravitational-wave Observatory (LIGO) have confirmed the detection of a third gravitational-wave signal from a pair of coalescing black holes. Read the story on or Caltech’s press release. Check the LIGO website for details about this latest detection.