PROJECTS
GW170817: First gravitational wave from binary neutron stars and electromagnetic spectrum
I am part of 1M2H team, lead by Ryan Foley. We, along incredible astronomers all over the globe, found the first optical light from a binary neutron star merger.
This incredible event was observed from gamma-rays to radio, and showed that the merger of neutron stars can result in the most powerful explosions in the universe: short-gamma ray bursts!
More info here!
Related papers:
Electromagnetic evidence that SSS17a is the result of a binary neutron star merger, Kilpatrick, C. D., et al. inc. Murguia-Berthier, A. 2017, Science, 358, 1583
Early spectra of the gravitational wave source GW170817: Evolution of a neutron star merger, Shappee, B. J., et al. inc. Murguia-Berthier, A. 2017, Science, 358, 1574
Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis, Drout, M. R., et al. inc. Murguia-Berthier, A. 2017, Science, 358, 1570
Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source, Coulter, D. A., et al. inc. Murguia-Berthier A. 2017, Science, 358, 1556
A gravitational-wave standard siren measurement of the Hubble constant, Abbott, B. P., et al. inc. Murguia-Berthier, A. 2017, Nature, 551, 85
A Neutron Star Binary Merger Model for GW170817/GRB 170817A/SSS17a, Murguia-Berthier, A. , A., Ramirez-Ruiz, E., et al. 2017, ApJ Letters, 848, L34
The Old Host-galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational-wave Source, Pan, Y.-C., et al. inc. Murguia-Berthier, A. 2017, ApJ Letters, 848, L30
The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational-wave Source, Siebert, M. R., et al. inc. Murguia-Berthier, A. 2017, ApJ Letters, 848, L26
Multi-messenger Observations of a Binary Neutron Star Merger, Abbott, B. P., et al. inc. Murguia-Berthier, A. 2017, ApJ Letters, 848, L12
Neutrino physics in binary neutron star mergers
A binary neutron star merger can result in an accretion disk surrounding a black hole. This accretion disk will produce a copious amount of neutrinos that will carry energy away, cool the disk and produce an outflow. As the outflow expands and cools, heavy elements will be created and will later radioactively decay, and we can observe them. We need simulations that make use of general relativistic magneto-hydrodynamics (GRMHD) with a neutrino treatment in order to get the final abundance of elements. As part of my thesis, I added a way in which to treat the impact of neutrinos and a finite temperature equation of state in a GRMHD code called HARM3D. We will use this new setup to obtain the abundance of elements in the outflows produced by the accretion disk. This is part of a TCAN collaboration, read more about this here!
Related papers:
Post merger simulations of binary neutron star mergers, Murguia-Berthier, S.C Noble, L. F. Roberts, et al. 2020, in prep
Interaction of gamma-ray burst jets with winds
After the binary neutron star merger, one of the possibilities is that the remnant is hyper-massive neutron star that will collapse into a black hole after some delay time (some ms). There will be transport of mass and angular momentum outward that will drive several winds during the neutron star phase. After it collapses to a black hole, a relativistic, beamed jet will be launched that will interact with the winds. I'm interested in this interaction, on how the wind slows down the jet and if it is dense enough, the wind can even choke the jet.
Related papers:
The Fate of the Merger Remnant in GW170817 and its Imprint on the Jet Structure, Murguia-Berthier, A. , Ramirez-Ruiz, E., De Colle, F., et al. 2020, arXiv:2007.12245
The Properties of Short Gamma-Ray Burst Jets Triggered by Neutron Star Mergers, Murguia-Berthier, A. , Ramirez-Ruiz, E., Montes, G., et al. 2017, ApJ Letters, 835, L34
Necessary Conditions for Short Gamma-Ray Burst Production in Binary Neutron Star Mergers, Murguia-Berthier, A. , Montes, G., Ramirez-Ruiz, E., et al. 2014, ApJ Letters, 788, L8
Maximum angular momentum of disappearing stars
We have tentative evidence of massive stars that disappear without a bright transient. It is commonly argued that this massive stars have low angular momentum and can collapse into a black hole without significant feedback. I made use of general-relativistic hydrodynamical simulations to understand the flow around a newly-formed black hole. With the simulations, we found the angular momentum needed in order for the infalling material to be accreted into the black hole without forming a centrifugally supported structure, thus generating no effective feedback. If the feedback from the black hole is significant, the collapse can be halted and, as a result, it is likely followed by a bright transient. With the results from the simulation, we constrained the maximum rotation rate for the disappearing massive progenitors know, and set a limit on the rate of expected disappearing stars.
Related papers:
On the maximum stellar rotation to form a black hole without an accompanying luminous transient, Murguia-Berthier, A., Batta, A., Janiuk, A., et al. 2020, ApJ Letters, 901, L24
Common envelope evolution
In a binary system of stars, when one of them evolves and grows in size, it can engulf its companion. Drag forces on the companion from the envelope of the primary will slow the companion and shrink the orbit. The change in orbital energy energy will be given into the envelope. Depending on this energy, the envelope can be ejected and the system will consist of the binary with a tighter orbit, or if the change in energy is not enough, a merger will occur. Studying common envelope and the energy transfer onto the envelope is important because it is one of the formation channels for binary black holes that LIGO detects and binary neutron star mergers.
I'm really interested in understanding how the gas from the envelope flows around the companion. I have studied in particular through numerical simulations how the microphysics affects the formation of accretion disks around the companion.
Related papers:
Accretion Disk Assembly During Common Envelope Evolution: Implications for Feedback and LIGO Binary Black Hole Formation, Murguia-Berthier, A. , MacLeod, M., Ramirez-Ruiz, E., et al. 2017, ApJ, 845, 173
Common Envelope Wind Tunnel: Coefficients of Drag and Accretion in a Simplifed Context for Studying Flows around Objects Embedded within Stellar Envelopes, MacLeod, M., Antoni, A., Murguia-Berthier, A. , et al. 2017, ApJ, 838, 56