Noise to signal

Results of LIGO O2 continuous gravitational waves on arXiv/ADS

2019-03-09T00:00:00+01:00

Narrow-band search for gravitational waves from known pulsars using the second LIGO observing run
Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015-2017 LIGO Data
All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO O2 data

The O2 data is now released and publicly available at the GWOSC.

G2net, a network of gravitational waves, geophysics and machine learning

2019-02-20T00:00:00+01:00

A new COST action G2net, dedicated to the synergy between GW astronomy, machine learning and geophysics (since our detectors are located on the ground) has just starting. Exciting times! :-)

There are three working groups:

WG1: Machine Learning for Gravitational Wave astronomy
WG2: Machine Learning for low-frequency seismic measurement
WG3: Machine Learning for Advanced Control techniques

with funding available for Short Term Scientific Missions and Inclusiveness Target Countries conference grants. If you are interested, write to me.

Incoming: Data Science in (Astro)particle Physics and Cosmology (25-29 March 2019) school in Braga, Portugal, co-funded and organized by G2net.

Find unused \bibitem in LaTeX documents

2018-07-06T00:00:00+02:00

In case of \bibitem style bibligraphies in LaTeX, here’s a small script to find currently not used references (e.g. not commented out). It compares the .aux file and the .tex file):

import sys
import re

# .tex and .aux files 
tex = sys.argv[1] + ".tex"
aux = sys.argv[1] + ".aux"

# search for lines with "\citation" in aux  
# split and flatten needed for cases of multiple citations, e.g. \cite{A,B,C}  
laux = [re.search('citation{(.*)}', line).group(1).split(',') for line in open(aux) if "\\citation{" in line]

# flatten list  
laux = [x for sl in laux for x in sl]

# search for lines with "\bibitem" but not "%\bibitem" in tex
ltex = [re.search(']{(.*)}', line).group(1) for line in open(tex) if "\\bibitem" in line and not line[0] == "%"]

# result: 
print("This bibitems are not used: {}".format(sorted(set(ltex) - set(laux))))

Howto run:

python script.py yourfilename

That day when I was an expert on Nicolaus Copernicus

2018-05-24T00:00:00+02:00

I was interviewed at length in Polish and a bit shorter in English. This was fun :-)

Full band all-sky search for periodic gravitational waves in the O1 LIGO data article accepted to PRD

2018-05-11T00:00:00+02:00

We report on a new all-sky search for periodic gravitational waves in the frequency band 475–2000 Hz and with a frequency time derivative in the range of $[-1.0, +0.1]\times 10^{-8}$ Hz/s. Potential signals could be produced by a nearby spinning and slightly non-axisymmetric isolated neutron star in our galaxy. This search uses the data from Advanced LIGO’s first observational run O1. No gravitational wave signals were observed, and upper limits were placed on their strengths. For completeness, results from the separately published low frequency search 20–475 Hz are included as well. Our lowest upper limit on worst-case (linearly polarized) strain amplitude $h_0$ is ${\sim} 4\times 10^{-25}$ near 170 Hz, while at the high end of our frequency range we achieve a worst-case upper limit of ${1.3}\times 10^{-24}$. For a circularly polarized source (most favorable orientation), the smallest upper limit obtained is ${\sim}{1.5}\times 10^{-25}$.

See also:

List of LIGO-Virgo detection and companion papers

2017-12-10T00:00:00+01:00

Check out this link.

Wednesday seminar at CTP PAS about the GW170817 signal

2017-11-22T00:00:00+01:00

Here is a youtube recording of my talk about the first binary neutron-star merger detected by LIGO and Virgo.

I am reporting on a recent breakthrough, historically-first observation of gravitational waves from a merger of neutron stars registered by the LIGO-Virgo network, and related wide-spectrum observations in electromagnetic waves range of resulting short gamma ray burst, X-ray afterglow, optical kilonova etc. These joint observations constitute a beginning of the multi-messenger astronomy. Results derived from this single observations include, among others, the first ‘‘standard siren’’ measurement of the Hubble constant and the expansion rate of the Universe independent of traditional distance ladders, constraints on the equation of state of dense matter and measurement of the speed of gravitational waves.

Joint Advanced LIGO-Advanced Virgo observing run O2 ends

2017-08-25T00:00:00+02:00

A very exciting LIGO-Virgo Observing run draws to a close on the 25th of August. The Virgo and LIGO Scientific Collaborations have been observing since November 30, 2016 in the second Advanced Detector Observing Run ‘O2’, searching for gravitational-wave signals, first with the two LIGO detectors, then with both LIGO and Virgo instruments operating together since August 1, 2017. Some promising gravitational-wave candidates have been identified in data from both LIGO and Virgo during our preliminary analysis, and we have shared what we currently know with astronomical observing partners. We are working hard to assure that the candidates are valid gravitational-wave events, and it will require time to establish the level of confidence needed to bring any results to the scientific community and the greater public.

See also:

Advanced Virgo news

Low-frequency all-sky search for periodic GWs in LIGO O1 article accepted to PRD

2017-08-08T00:00:00+02:00

A collection of data-analysis methods (including the Time Domain F-statistic) is used to establish upper limits on the gravitational wave emission from unknown sources of periodic waves e.g., rotating deformed on unstable neutron stars.

We report on an all-sky search for periodic gravitational waves in the frequency band 20-475 Hz and with a frequency time derivative in the range of $[-1.0, +0.1]\ 10^{-8}$ Hz/s. Such a signal could be produced by a nearby spinning and slightly non-axisymmetric isolated neutron star in our galaxy. This search uses the data from Advanced LIGO’s first observational run, O1. No periodic gravitational wave signals were observed, and upper limits were placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude $h_0$ are $4\times 10^{-25}$ near 170 Hz. For a circularly polarized source (most favorable orientation), the smallest upper limits obtained are $1.5\times 10^{-25}$. These upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest upper limits obtained for the strain amplitude are $2.5\times 10^{-25}$.

See also:

Inauguration of the Advanced Virgo gravitational-wave detector

2017-02-20T00:00:00+01:00

On the 20th of February 2017 the installation of the Advanced Virgo has concluded :-D

This does not mean the detector will immediately start collecting science data - some time is needed for various commissioning. Depending on how it will go, Virgo will try to join Advanced LIGO sometime before the end of the O2 run (i.e. before the summer).

See also:

Advanced Virgo: a 2nd generation interferometric gravitational wave detector
Another Gravitational Wave Detector Will Help Revolutionize Astronomy
LIGO’s underdog cousin ready to enhance gravitational-wave hunt (…Nature and their ‘catchy’ titles… ¯\(ツ)/¯ )