Journal Club


"GW190425: Observation of a Compact Binary Coalescence with Total Mass ∼3.4 solar masses"

Michal Bejger (CAMK, Warsaw)

The speaker will talk about the recent LVC paper on the first public detection from O3.


"Sausage & Mash: the dual origin of the Galactic thick disc and halo from the gas-rich Gaia-Enceladus-Sausage merger"

Rodolfo Smiljanic (CAMK, Warsaw)

The speaker will report on the recent work , where the authors analyse a set of cosmological magneto-hydrodynamic simulations of the formation of Milky Way-mass galaxies identified to have a prominent radially anisotropic stellar halo component similar to the so-called "Gaia Sausage" found in the Gaia data.


"Core and crust contributions in overshooting pulsar glitches"

Alessandro Montoli (Universita' degli Studi di Milano)

During a pulsar glitch the angular velocity of the neutron star may overshoot, namely reach values greater than that of the new post-glitch equilibrium. Fitting the data of the 2016 glitch of the Vela pulsar, it is possible to obtain estimates for the moments of inertia of the internal superfluid components involved in the glitch. Preliminary results imply a reservoir of angular momentum extending beyond the crust and an inner core of non-superfluid matter. The talk will be based on:


"A Quake Quenching the Vela Pulsar"

Jose Ortuno Macias (CAMK, Warsaw)

The remarkable null pulse coincident with the 2016 glitch in Vela rotation indicates a dynamical event involving the crust and the magnetosphere of the neutron star, probably linked to seismic activity in the crust. The talk will be based


"VLTI/GRAVITY observations of the Galactic Center"

Krzysztof Nalewajko (CAMK, Warsaw)

I will present the results of extremely precise astrometric near-infrared observations of the Galactic Center, including the massive black hole Sgr A* and a nearby star S2 around its pericenter passage in May 2018, with the GRAVITY instrument on the ESO Very Large Telescope Interferometer. These results have been presented in the following publications: , , , ,


"New Discoveries regarding Fast Radio Bursts"

Morgane Fortin (CAMK, Warsaw)

The speaker will update us on the newest discoveries about FGRBs. The talk will be delivered in the seminar room and will be based on: "Periodic activity from a fast radio burst source" by the CHIME/FRB Collaboration


"Debates on the 70 Solar mass Black Hole LB-1"

Qiang Chen (CAMK, Warsaw)

The JC will be delivered on-line (Zoom Meeting). The talk will be based on: , ,


"BLR size and R-L relation in realistic FRADO model"

Mohammad Naddaf (CAMK, Warsaw)

The talk is based on: and will be delivered on-line (Zoom Meeting).


"Light curves of tidal disruption events in active galactic nuclei"

Ruchi Mishra (CAMK, Warsaw)

The talk is based on The JC will be on-line ( Zoom Meeting ).


"JAGB (J-region Asymptotic Giant Branch) stars as primary distance indicators"

Piotr Wielgorski (CAMK, Warsaw)

The talk will be based on: and


"Bringing General Relativity into the Laboratory"

Jonas Pereira (CAMK, Warsaw)

I will explain how some aspects of, e.g., astrophysics, cosmology and quantum field theory in curved spacetimes could be effectively reproduced and probed with the use of metamaterials (man-made media with controllable dielectric coefficients). In addition, I'll try to quickly elaborate on how experimental efforts into this direction might also help advance important technologies.


"Astronomical signatures at the world’s first temple: Göbekli tepe"

Filiz Kahraman (CAMK, Warsaw)

Göbekli Tepe ("Potbelly Hill") is an archaeological site in the Southeastern Anatolia Region of Turkey approximately 12 km (7 mi) northeast of the city of Şanlıurfa. Dr. Kahraman will tell us about the astronomical knowledge of the first inhabitants of this UNESCO site.


"Rotating neutron stars with non-barotropic thermal profile"

Giovanni Camelio (CAMK, Warsaw)

Being able to determine the stationary structure of a neutron star allows to study its properties, like the parameter space of the equation of state, the mass-radius diagram, and the gravitational wave emission. Moreover, this stationary configuration can be used as initial condition for a much more resource demanding hydrodynamical simulation. A key approximation made for computing the stationary structure of hot and rotating neutron stars is that of barotropicity, namely that all thermodynamical quantities are in a one-to-one relationship, which in turn implies that the specific angular momentum of a fluid element is in a one-to-one relationship with its angular velocity. However, this is a poor approximation for the compact remnant of a core-collapse supernova or of a binary neutron star merger. In this talk I describe how, for the first time, we determine the structure of stationary, hot, rotating neutron stars without the barotropic approximation. To do so, we introduce a potential formulation for the Euler equation, which is a novel technique even in the context of Newtonian stars. Coauthors: Tim Dietrich, Miguel Marques, Stephan Rosswog Paper: arXiv:1908.11258 - Camelio, Dietrich, Marques & Rosswog, PRD 100:123001 (2019).


"Ecological Impact of High-performance Computing"

Miljenko Cemeljic (CAMK, Warsaw)

The talk is based on: "The Ecological Impact of High-performance Computing in Astrophysics" by Portegies Zwart, S. "An astronomical institute’s perspective on meeting the challenges of the climate crisis" by Jahnke, K. et al., The JC will be on-line (Zoom Meeting).


"Directed search for continuous gravitational wave signals from the Galactic Center"

Ornella Juliana Piccinni (INFN - Istituto Nazionale di Fisica Nucleare, Rome)

In this work we present the results of a search for continuous gravitational waves from the Galactic Center using LIGO O2 data. The search uses the Band-Sampled-Data directed search pipeline, which performs a semi-coherent wide-parameter-space search, exploiting the robustness of the FrequencyHough transform algorithm. The search targets signals emitted by isolated asymmetric spinning neutron stars, located within 25-150 parsecs from the Galactic Center. The talk will be based on:


"Big and young SMBHs in the early Universe: The first blazar observed at z>6"

Tullia Sbarrato (INAF - Osservatorio Astronomico di Brera (Merate, Italy))

The existence of extremely massive black holes at very high redshift is a true challenge to the commonly accepted black hole formation and evolution models. The quasars found at z>4 host extremely massive black holes and are particularly problematic: there is not enough time to accrete such large masses in a standard scenario. The presence of a jet could speed up the accretion process enough to assemble 10^9 solar masses black holes before z~6 from a reasonable black hole seed. Studying the population of jetted quasars is hence necessary. The peculiar orientation of blazars makes them the most effective tracers of the whole jetted population. Do relativistic jets really have a role in the early formation of extremely massive black holes? To explore the matter, we present the discovery of PSO J0309+27, a source selected by cross-matching NVSS and PanSTARRS PS1, whose high-z nature was confirmed by a dedicated spectroscopic observation at LBT. Swift/XRT, VLA and VLBA observations allowed us to classify this source as the farthest blazar currently known, putting even more extreme constraints on the formation and evolution of the first supermassive black holes in our Universe.


"The nature of the Milky Way's halo revealed by the three integrals of motion"

André Rodrigo da Silva (CAMK, Warsaw)

Based on a new selection method of halo stars in the Milky Way local volume, the general chemo-dynamical structure of the stellar halo is explored. The method relies on the phase-space distribution defined by the three integrals of motion in an axisymmetric Galactic potential. The talk is based on: "The nature of the Milky Way's halo revealed by the three integrals of motion" by Carollo, Daniela and Chiba, Masashi, e-print: arXiv:2010.00235


"Neutron stars and scalar-tensor theories"

Jacopo Soldateschi (INAF Osservatorio di Arcetri, Florence)

Among the most promising “alternative theories of gravity”, one of the most studied class is that of the “scalar-tensor theories” (STTs), because they are the most simple extensions of general relativity (GR), they don’t lead to pathologies in the spacetime properties, and show behaviours that look promising in the context of cosmological constraints. Some of these theories predict a phenomenon known as “spontaneous scalarisation”, which produces strong deviations from GR in compact objects (like NSs) while fulfilling the strong observational constraints in the weak gravity regime. Such phenomenon is potentially observable in this new era of gravitational waves (GWs) astronomy. I will present the results we obtained in the scenario of numerical multi-dimensional modelling of NSs in STTs, for the first time with the inclusion of magnetic fields, accomplished by the simultaneous solution of the coupled Scalar-Einstein-Maxwell equations. Our aim is to understand how global quantities (like the mass and the magnetic deformation), that are potentially observable, deviate from GR, in the hope of providing new tools to test these theories through future observations. Moreover, I will explain how these deviations translate to the emission of GWs. Finally, I will present the formalism of our algorithm, showing how it can be extended to include, in particular, realistic equations of state.