# The search for grawitational waves from isolated neutron stars

The LIGO-Virgo-KAGRA collaboration has published the results of the search for continuous gravitational waves in the data from the entire O3 observational campaign. It is expected that such waves can be emitted by e.g. axially asymmetric neutron stars, but their amplitude is much smaller than the regularly observed, short-term signals emitted during black hole mergers. For this reason, they have not been observed so far. In this publication, we present the results of four independent methods obtained by various research groups that carried out the so-called blind searches in a wide range of parameters: all sky, frequency range from 10 to 2048 Hz and rate of frequency change from $-10^{- 8}$ to $10^{- 9}$ Hz / s.

# First observations of ‘mixed’ black hole and neutron star pairs

The Virgo, LIGO and KAGRA scientific collaborations today announced the first observation ever of binary systems consisting of a neutron star (NS) and a black hole (BH). This was made possible by the detection, in January 2020, of gravitational signals (nicknamed GW200105 and GW200115 from the dates of their detection) emitted by two systems, in which a black hole and a neutron star, rotating around each other, merged into a single compact object.

# Over 100 black holes detected by Virgo and LIGO in the first run of 2019

The classification and definitive analysis of the 39 events detected by Virgo and LIGO in the third observation period (which ran from April to October 2019) was published today on the ArXiv online archive. Most of these are black hole mergers, the characteristics of which, however, question some established astrophysical models and open up new scenarios. A likely merger of neutron stars and two probable ‘mixed’ neutron star-black hole systems were also detected in the same period.

# GW190521 unveils new and unexpected black hole populations

Virgo and LIGO have announced the detection of an extraordinarily massive merging binary system: two black holes of 66 and 85 solar masses, which generated a final black hole of 142 solar masses. The remnant lies in a range of mass that has never before been observed, either via gravitational waves or with electromagnetic observations. The final black hole is the most massive ever detected with gravitational waves. The breaking of the mass record of the Virgo and LIGO observational runs is just one of the many special features that make the detection of this exceptional merger an unprecedented discovery.

# LIGO-Virgo observation period suspended because of COVID-19.

The LIGO Scientific Collaboration and the Virgo Collaboration (the LVC) have agreed to suspend their third observation period, named O3, which has been running since the 1st of April, 2019. The suspension, which will be effective within one week, is motivated by the worldwide COVID-19 pandemic. Public health and worker safety are always the top priority for the LVC. Read more

# GW190425: the merger of a compact binary with total mass of about 3.4 Msun.

On April the 25th, 2019, the network of gravitational-wave (GW) detectors formed by the European Advanced Virgo, in Italy, and the two Advanced LIGO, in the US, detected a signal, named GW190425. This is the second observation of a gravitational-wave signal consistent with the merger of a binary-neutron-star system after GW170817. GW190425 was detected at 08:18:05 UTC; about 40 minutes later the LIGO Scientific Collaboration and the Virgo Collaboration sent an alert to trigger follow-up telescope observations.