Top ten papers on the NSNS merger historic GW/EM event

Um tema de casa rápido para se fazer antes do nosso JC. O objetivo é criar um seleção dos top ten artigos sobre o evento NSNS merger (GW170817 / GRB170817 / kilonova):

  1. olhar as listas de papers publicados no PRL, ApJL, Science e Nature sobre o evento (ver links abaixo)
  2. escolher até dez artigos que você considera mais importantes para se ler sobre as descobertas (GW, prompt emission e kilonova)
  3. vamos comparar as escolhas que cada um fez durante a reunião e—depois de um cross-reference—decidir entre 7-10 artigos que nós vamos discutir nas próximas reuniões

Onde encontrar as listas de artigos

Comentários sobre os artigos no ApJL, Science e Nature

Our choice for top ten papers, updated Oct 19th

Google Docs link


Hint of quantum gravity effects on LIGO data; jet spectra from GRMHD simulations

We discussed two papers last week:

Both papers are very interesting.

Gustavo’s paper shows promising places in the multiwavelength SEDs of stellar-mass black holes where we could find evidence of jet emission. They implemented grmonty radiative transfer on top of HARM GRMHD simulations, painting the simulation with different electron/ion temperatures for the jet and accretion flow. Curiously, they find no QPOs at all in the emission. This is related to Gustavo’s PhD thesis work.

Rodrigo’s paper shows very interesting search for evidence of fuzzballs or firewalls near the event horizons, by searching the LIGO waveforms for the three detections so far. These membranes — which are very close to the horizon, a Planck length away — should reflect back to infinity the GWs produced during the ringdown phase, though I am completely unfamiliar with the physics of such membranes. This should produced periodic, GW echoes which could teach us about the physics of these “apparent horizons”. They find a 2sigma hint that the echoes are present in the GW150914 event, about 0.3 seconds after the merger.

Two things I would like to see:

  1. They should show a Figure 4 with a broader range of time, such that we could judge how the average noise is compared to the maximum amplitude of the possible echo
  2. If these echoes are really there, then they should show up in the wavelet periodogram with a frequency of ~3 Hz (see the slides I prepared). I am sure that the LIGO Collaboration is searching for this right now.

I find it suspect the way they combined the waveforms of three GW signals of mergers with different masses and found a 2.9sigma evidence of echoes.


Discussion of astrophysical implications of GW150914: March 11th, 2:30pm

Next week we will discuss the astrophysical implications/progenitors of the GW150914 event observed by LIGO. I invited some of the experts on stellar astrophysics in our department to join the discussion and we will have  Riccardo Sturani (IFT UNESP) from the LIGO Collaboration joining our discussion. It should be fun!
The papers we are planning to discuss are the following ones (links for the papers available here):
  • Astrophysical Implications of the Binary Black-Hole Merger GW150914 (ApJL)
  • The Progenitor of GW 150914 (ApJL, submitted)
  • The origin and evolution of LIGO’s first gravitational-wave source (Science, submitted)
Please go ahead and read one or more of these papers, such that you can understand and contribute to the discussion.
From the abstract of the first paper:
Such black-hole mergers [GW150914] have been predicted in two main types of formation models, involving isolated binaries in galactic fields or dynamical interactions in young and old dense stellar environments. The measured masses robustly demonstrate that relatively “heavy” black holes (25M25M) can form in nature. This discovery implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with metallicity lower than 1/212 of the solar value. The rate of binary black-hole mergers inferred from the observation of GW150914 is consistent with the higher end of rate predictions (1Gpc3yr11Gpc3yr1) from both types of formation models. The low measured redshift (z0.1z0.1) of GW150914 and the low inferred metallicity of the stellar progenitor imply either binary black-hole formation in a low-mass galaxy in the local Universe and a prompt merger, or formation at high redshift with a time delay between formation and merger of several Gyr. 
Join our conversation this Friday, March 11th, 2:30pm, sala G14. Don’t forget to have a look at the papers.
Looking forward to see you all next Friday at the usual time and place.


Como chegar na Sala G14 (torre G):
  • siga na direção do auditório do IAG, até o final do corredor
  • ao invés de descer as escadas, suba dois lances e você vai encontrar a sala G14

Origin of periodicity in binary SMBH candidate (Nature), 3D simulations of GRB jets

In our last meeting, we discussed two papers:

For the first paper, published last week in Nature, we had the opportunity to chat with the first author, Daniel D’Orazio, a phd student at Columbia finishing grad school. Daniel mentioned the motivation for the work, some of the challenges. We asked about comparisons of the variability behavior with a few other binary SMBH candidates, prospects for future studies, clues on the behaviour of the BLR for these guys.

Here is a very rough cartoon of the physical scenario by Rodrigo:

Evernote Snapshot 20150925 153026

Chandra told us about the second paper by Bromberg & Tchekhovskoy. Quite long but very interesting investigation of 3D GRMHD propagation of magnetised jets in GRBs. According to Chandra, the main result of the paper is in figure 8. He walked us through half of the paper.

fig 8 bromberg


Introducing Vox Charta

What is vox charta?

A website that facilitates the selection of papers for discussion in group meetings and journal clubs such as the Clube dos AGNs.

How does it work?

1. Sign up for USP AGN Vox Charta (see section just below on how to sign up)

2. Read “how to participate”

3. Vote early for papers that you find interesting. Read the abstracts of the papers you vote for and be ready to talk about why you voted for them

Vox_Charta 02

4. If you would like to present a paper, click “commit to present”


5. A day before the meeting, an e-mail will be sent to the mailing list with the agenda of voted papers

Vox_Charta 03

How to sign up for vox charta

Vox_Charta 01



A reconnection model for SEDs of LLAGNs in radio galaxies; new ARA&A by Netzer on the unified model; autobiographical ARA&A by M. Schmidt

Behrouz told us about his recently submitted paper:

Particle Acceleration and Gamma-ray emission due to magnetic reconnection in the core region of radio galaxies 

He can explain the multiwavelength SEDs of low-luminosity AGNs in radio galaxies with some kind of fast reconnection model. The nice feature of his model is that it accounts for the observed TeV emission (MAGIC, HESS). Some questions remain:

  • why would reconnection only be important for radio galaxies which have very strong jets which can certainly be a source of TeV photons?
  • what about the variability? he modeled the steady-state (not flaring) emission of these objects but wouldn’t reconnection predict flaring emission?
  • can thin disks advect enough B to create reconnection in the inner regions?

Papers that I went through very briefly

Merger-driven Fueling of Active Galactic Nuclei: Six Dual and Offset Active Galactic Nuclei Discovered with Chandra and Hubble Space Telescope Observations 

Revisiting the Unified Model of Active Galactic Nuclei. The new ARA&A by Netzer on the unified model.

The Accretion Wind Model of the Fermi Bubbles (II): Radiation

Tidal disruption of stars by supermassive black holes: Status of observations

The Best Constraints on A Super-Eddington Accretion Flow: XMM-Newton Observations of An Intermediate-mass Black Hole

There is also an auto-biographical ARA&A written by Marteen Schmidt.

Other papers noticed

Circumnuclear Media and Accretion Rates of Quiescent Supermassive Black Holes

Insights on the Dusty Torus and Neutral Torus from Optical and X-ray Obscuration in a Complete Volume Limited Hard X-ray AGN Sample.


Strong magnetic field in a radio galaxy from RM; inside the Bondi radius of M87

Juliana talked about recent constraints on the rotation measure of a radio galaxy using ALMA observations. There is a degeneracy between the electron density and the magnetic field, so the observations cannot give an unambiguous measure of the B. But they suggest strong fields at sub-parsec scales.

A strong magnetic field in the jet base of a supermassive black hole, Science.

Rodrigo spoke about a paper recently accepted to MNRAS: Inside the bondi radius of M87. The authors select Chandra observations and are able to constrain the density and temperature profiles within the Bondi radius of M87. They don’t see a temperature rising — as would be expected from gravitational heating due to the presence of the SMBH — and find rho(R) \propto 1/R as would be expected in RIAF models with outflows. This is another paper strengthening the case that the Bondi model is simple and attractive, but unrealistic and unlikely to be valid in the real world of SMBH accretion in LLAGNs.

Other papers we noticed

A New Catalogue of Type 1 AGN and its Implication on the AGN Unified Model


Coevolution Between Supermassive Black Holes and Bulges Is Not Via Internal Feedback Regulation But By Rationed Gas Supply Due To Angular Momentum Distribution


The Best Constraints on A Super-Eddington Accretion Flow: XMM-Newton Observations of An Intermediate-mass Black Hole


X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk?


Comparison between RHD simulation of supercritical accretion flows and steady model with outflows


Merger-driven Fueling of Active Galactic Nuclei: Six Dual and Offset Active Galactic Nuclei Discovered with Chandra and Hubble Space Telescope Observations


Stellar and Quasar Feedback in Concert: Effects on AGN Accretion, Obscuration, and Outflows


Winds from a nearby quasar; reverberation mapping of super-critical AGNs; search for extraterrestrial civilizations using WISE

In this interesting meeting, we discussed the following papers. Steiner spoke about the detection of a P-cygni profile in the X-ray emission from the z=0.2 quasar PDS 456 (Nardini et al. 2015, Science paper). This is significant because P-cygni profiles are the signatures of outflows — either in stars or in AGNs. The beautiful XMM and Nustar observations are consistent with an accretion disk moving at ~0.3c and carrying 1E46 erg/s of kinetic power which is comparable to the binding energy of a Milky Way type of galaxy. Note that this paper is very much related to the previous Tombesi et al. 2015 Nature paper that we discussed a few weeks ago.

Here is a comparison of the X-ray spectra reported by Tombesi (Nature) and Nardini (Science):

Henrique spoke about the result that the time delays between continuum and line emission in highly super-Eddington AGNs in NLSy1s tend to be smaller than in sub-Eddington Seyferts. Is the broad line much different / smaller in size in NLSy1s? What is going on?

Rodrigo talked about the new ApJ paper on searching for the waste heat from type-III civilizations in the mid-IR using the WISE (arXiv:1504.03418). This kind of study should be done and the cool thing is that there are secondary science products (finding weird IR emitters). They find about 100 extended sources with an excess of mid-IR emission. This paper has received quite some coverage in the press (e.g., VISION, Penn State press release). Jason Wright (PI of the G-hat project) has been blogging about this for a while, definitely an interesting read.

Other papers that we noticed

Heating the intra-cluster medium by jet-inflated bubbles

The Nuclear Structure of 3C84 with Space VLBI (RadioAstron) Observations

The Energetics and Lifetimes of Local Radio Active Galactic Nuclei


First meeting of the year: Accretion disk winds and quasar feedback; 10 billion solar masses black hole at z=6.3

We discussed two Nature papers. One was published last week and the other a couple of weeks ago.

An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30, Nature

João presented the Nature paper An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30, Nature

Weak points: identification of quasar by colors (came from SDSS); application of local reverberation mapping scaling to such object at high-z is risky.

This paper has been featured quite a lot in the news lately. See also the feature:Feature: A giant in the young universe.

Wind from black hole accretion disk as the driver of a molecular outflow in a galaxy, Nature

Rodrigo presented the Nature paper by Tombesi et al. This paper was expected to be published at anytime and made it into the cover of the magazine on March 25th.


First time, as far as I know, that the origin of large-scale molecular outflows which are associated with quasar feedback in ULIRGs — operating in scales of hundreds of pc — is connected with an origin in the accretion disk winds coming from scales of 1E-4 pc (~100 Schwarzschild radii). Energetics is consistent between the two outflows and the inner wind has speeds of ~0.2c. Inner wind observed via absorption in Suzaku X-ray spectrum while large-scale outflows comes from absorption seen with Herschel.

UFOs are not a consensus among X-ray “spectroscopists” and some believe they are a statistical fluke.

A vigorous discussion followed involving Bete and Claudio. They argued that the interpretation put forward by Tombesi et al. of the observations is not favored. From what I could understand from their arguments, they favor a starburst origin for the wind or a jet origin both of which do not seem to be favored by the observations of the mildly relativistic inner wind and the fact that ULIRGs are generally radio-quiet.

Other papers we noticed

Powerful Outflows and Feedback from Active Galactic Nuclei, ARA&A
Polarization Swings Reveal Magnetic Energy Dissipation in Blazars
Black hole feedback in the luminous quasar PDS 456, Science (the “brazilian” quasar)
(this one will be discussed in a future meeting)

One of the articles in the special edition of Science: GR Turns 100
A Planck-scale limit on spacetime fuzziness and stochastic Lorentz invariance violation, Nature Physics