Galaxy Zoo Talk

# (Possible) Gravitational Waves Announcement Thurs

• by Budgieye moderator

Scientists are holding a news conference Thursday Feb. 11 2015 15:30 GMT)

Astronomers may finally have found elusive gravitational waves, the
mysterious ripples in the fabric of spacetime whose existence was
first predicted by Albert Einstein in 1916, in his famous theory of
general relativity.

Scientists are holding a news conference Thursday (Feb. 11) at 10:30
a.m. EST (1530 GMT) at the National Press Club in Washington, D.C., to
discuss the search for gravitational waves, which zoom through space
at the speed of light.

http://www.space.com/31869-gravitational-waves-news-conference-thursday.html

This would be the detection of two heavy objects merging ie. two neutron stars (most likely), a neutron star and a black hole, or less likely, two black holes. The most amazing would be the
merger of two supermassive Black Holes, such as found in the center of galaxies, but that is statistically unlikely.

http://www.sciencemag.org/news/2016/02/woohoo-email-stokes-rumor-gravitational-waves-have-been-spotted

Posted

• by c_cld

Association with an electromagnetic detection asked to ESO:

Proposal Title

Searching for the electromagnetic counterpart of gravitational wave sources

Night 2015 Sep 17 😃

Posted

• You're cunning 😃

Posted

• by c_cld

Sky localization targets in constellation Volans on Night 2015 Sep 17 (list of 108)

from Vizier "B/eso/eso_arc" Full ESO science archive log

Posted

• by c_cld

Targeted in December 28, 2015 (list of 292 )

http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=096.D-0110(A)

Posted

• by c_cld

Wonder what is the blue elongated object we see in http://www.worldwidetelescope.org/webclient/ near target ra,dec 08 28 22.77 -67 26 25.6 ?

Posted

• by c_cld

Multiple ESO observations of 08 28 22.77 -67 26 25.6

Obs RAJ2000 DEJ2000

2015-11-18T06:40:22 08 28 22.77 -67 26 25.6

2015-10-03T07:45:17 08 28 22.77 -67 26 25.6

2015-09-25T08:50:47 08 28 22.77 -67 26 25.6

2015-09-22T09:20:59 08 28 22.77 -67 26 25.6

2015-09-17T09:03:32 08 28 22.77 -67 26 25.6

2015-09-18T09:10:40 08 28 22.77 -67 26 25.6

Posted

• EDIT 10-02-2016

Maybe 2 / 4 interacting objects nearby ra,dec 127.095 -67.455 / 08:28:22.800 -67:27:18.00??

Images NED, (Edit not SDSS, but) DSS DR2 colored, red and blue

http://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=204198408&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1

Posted

• by c_cld

Back to Einstein's announcement 😃

Notion of gravitation waves first published by Albert Einstein in 1916 and 1918:

Über Gravitationswellen Jan 31, 1918

Paper solving "Einstein's equations" by a perturbation method where the special metric is a small deviation from the Euclidean metric. There are plane wave solutions that propagate at the velocity of light in vacuum and all physical effects are transverse to the propagation.

Posted

• by c_cld

Observation of Gravitational Waves from a Binary Black Hole Merger

B. P. Abbottetal.*(LIGO Scientific Collaboration and Virgo Collaboration)

(Received 21 January 2016; published 11 February 2016)

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-WaveObservatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410 +160−180 Mpc corresponding to a redshift z ¼0.09þ 0.03−0.04.In the source frame, the initial black hole masses are 36 +5−4M⊙and 29 +4−4M⊙, and the final black hole mass is 62 +4−4M⊙,with 3.0 +0.5−0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals.These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

DOI:10.1103/PhysRevLett.116.061102

Posted

• by c_cld

Astronomy Picture of the Day http://apod.nasa.gov/apod/astropix.html

event GW150914

LIGO Detects Gravitational Waves from Merging Black Holes

Illustration Credit: LIGO, NSF, Aurore Simonnet (Sonoma State U.)

The featured illustration depicts the two merging black holes with the signal strength of the two detectors over 0.3 seconds superimposed across the bottom.

Posted

• From space.com

The probable location of a black hole collision that spawned gravitational waves detected by the Laser Interferometer Gravitational-Wave Observatory is shown in this still from a National Science Foundation press conference in Washington, D.C. on Feb. 11, 2016. The collision occurred 1.3 billion years ago in a region of space over Earth's Southern Hemisphere, scientists say.
Credit: National Science Foundation

Any general coordinates known?

Posted

• by Budgieye moderator

That is a good map for the location of the event. Thanks Ghost Sheep. Somewhere around the Great Magellanic Cloud. So we won't be finding it in SDSS or DECaLS.

Posted

• A far better localization map

http://astrog80.astro.cf.ac.uk/Gravoscope/#

Gravoscope allows you to overlay the projected possible locations of gravitational waves detected by Advanced LIGO. Use the options in the bottom left to turn them on and off. The positions cover large areas of sky because trangulation of gravitational wave signals is very difficult, and the location is only constrained to an area on the sky. The more likely regions are brighter.

Posted

• Large Magellanic Cloud;

Right ascension 05h 23m 34.5s

Declination −69° 45′ 22″

https://en.m.wikipedia.org/wiki/Large_Magellanic_Cloud

Well (ra,dec 127.095 -67.455 / 08:28:22.800 -67:27:18.00) still in the neighbourhood, 1 day for before the announcement 😃 , you're amazing c_cld

Posted

• by c_cld

From LIGO

@LIGO Feb 12 Rai Weiss will give a colloquium today at 1pm EST on
#GravitationalWaves to @NSF.

5:55 PM - 12 Feb 2016

Georgia, USA

https://youtu.be/c7293kAiPZw (poor quality video recording)

LIGO co-founder Rai Weiss talks about the complicated history of
gravitational waves, a little about the LIGO detector and the
discovery, and a bit about the future.

Prof. Rai Weiss tells a little of history in which he puts the timeline of "Theorists", "Observers" and "Experimentalists" back to A.Einstein up to groups of "architects" in the 70's.

He emphasizes the role of the "Chapel Hill meeting" but forgets to mention women.
This big event happened in 1957 which reinvigorated studies in this GW/GR field.

He should have excerpted from the Cécile M. DeWitt's "Report from the 1957 Chapel Hill Conference"

a quote from R. H. Dicke "we have Eddington’s view, which I may describe by saying that if we make the mathematics complicated enough, we can expect to make things fit."

instead of R.Weiss quote about skeptical Eddington '... waves were spurious and propagate ... with the speed of thought.’

More importantly he should have speak of the session "Solving The Initial Value Problem Using Cartan Calculus / Mme Choquet-Bruhat"
and the discussion summarized by Misner

“First we assume that you have a computing machine better than
anything we have now, and many programmers and a lot of money, and you
want to look at a nice pretty solution of the Einstein equations. The
computer wants to know from you what are the values of gμν and ∂ gμν ∂
t at some initial surface,say at t = 0. Now, if you don’t watch out
when you specify these initial conditions, then either the programmer
will shoot himself or the machine will blow up. In order to avoid this
calamity you must make sure that the initial conditions which you
prescribe are in accord with certain differential equations in their
dependence on x,y, z at the initial time. These are what are called
the “constraints.” They are the equations analogous to but much more
complicated than div−→E =0. They are the equations to which we have
been finding particular solutions; and on the other hand, Mme Fourès
has shown the existence of more general kinds of solutions. Mme
Fourès has told us that to get these initial conditions you must
specify something else on a two-dimensional surface and hand over that
problem, the problem of the initial values, to a smaller computer
first, before you start on what Lichnerowicz called the evolutionary
problem. The small computer would prepare the initial conditions for
the big one. Then the theory, while not guaranteeing solutions for the
whole future, says that it will be some finite time before anything
blows up.”

We might regret Prof. Reiss doesn't highlight support of solving the most complex problems in numerical relativity and relativistic astrophysics, including several groups addressing models of gravitational waves sources seen by LIGO in this discovery. 😃

Posted

• by c_cld

DES searches for optical signatures of gravitational waves

Results of analyses can be found in Soares-Santos et. al 2016 and Annis et. al 2016.

Area covered by the DECam searches for optical counterparts of the first gravitational wave event #GW150914.

The dotted contours show the initial (September 2015) skyprobcc cWB complete map, while the solid contours are for the ﬁnal (January 2016) LALInference skymap. The hexagonal DECam ﬁelds observed are shown, with red for the main search and orange for the short exposure LMC data. The projection shown is an equal-area McBryde-Thomas ﬂat-polar quartic projection.

Conclusions

over the analysis region covering 3% of the total localization probability, we ﬁnd no candidate counterparts.

... Although these results are not surprising given the partial areal
coverage and the likely BBH merger nature of the event, our search is
a crucial ﬁrst step and demonstrates the viability of DECam for deep
optical follow-up of GW events.

Posted

• by c_cld

GW150914 Factsheet

contribution of the Gravitational Physics Group at Cardiff University

Space-time ripples detected for the very first time

Posted

• by c_cld

From the The French Académie des Sciences

L'Académie des sciences salue la naissance d'une nouvelle astronomie

Une nouvelle fenêtre s’ouvre sur l’Univers. Un siècle après leur prédiction par Einstein, des ondes gravitationnelles en provenance de l’Univers lointain viennent d’être détectées sur Terre, apportant pour la première fois une preuve directe de l’existence des trous noirs.

Depuis les années 60, les ondes gravitationnelles faisaient l’objet de recherches intensives par la mise en œuvre de détecteurs mécaniques résonnants, puis de gigantesques interféromètres optiques. La réalité de la propagation par ondes de la gravitation a été établie dans les années 80-90, grâce à l’observation du mouvement de plusieurs pulsars binaires. Cependant, leur émission hors du système n’avait encore pu être détectée. Les ondes gravitationnelles sont des déformations de l’espace-temps extraordinairement petites, qui se propagent à la vitesse de la lumière. Elles proviennent de sources astrophysiques d’une puissance extrême, telle la coalescence de systèmes binaires d’astres très compacts comme les trous noirs ou les étoiles à neutrons. Fin 2015, des fluctuations, d’un facteur relatif de l’ordre de 10-21, ont été enregistrées dans la longueur des deux bras d’un interféromètre de Michelson muni de cavités Fabry-Pérot. Ces signaux n’ont duré qu’une petite fraction de seconde, mais leur forme portait la signature de leur source : la coalescence de deux trous noirs ayant une masse de l’ordre de 30 masses solaires, et situés à environ 400 Mpc (1 parsec (pc) ≈ 3,26 années-lumière) de la Terre. Cette découverte constitue deux grandes premières : la détection d’ondes gravitationnelles et l’observation de la fusion de deux trous noirs, en parfait accord avec la dynamique de ces objets prédite par la relativité générale. Un accord qui apporte une nouvelle confirmation de la théorie d’Einstein dans un régime encore inexploré. Ces observations de fin 2015 ont été effectuées sur les deux interféromètres LIGO situés aux États-Unis, appartenant au réseau international LIGO/Virgo. Ce réseau de détecteurs est né d’une collaboration entre les États-Unis, la France et l’Italie, notamment. Six équipes françaises ont ainsi participé à cette découverte qui repose, par ailleurs, sur l’utilisation d’éléments clés initiés en France : transfert de stabilité par injection, choix d’un laser YAG, modélisation optique de l’interféromètre, utilisation d’un « mode-cleaner », traitement optique à faible perte des miroirs, algorithmes robustes de recherche de signaux inconnus transitoires, extraction des signaux gravitationnels par filtrage adapté utilisant des gabarits fondés sur la méthode EOB.
Des études sont en cours pour améliorer encore la sensibilité des interféromètres afin d’accéder à un plus grand nombre de sources. Le domaine des basses et ultrabasses fréquences, inaccessible sur Terre, pourra être couvert par d’autres détecteurs : interféromètres de très grande envergure dans l’espace (eLISA), réseau de pulsars milliseconde, dispositifs d’étude de la polarisation du fond radio cosmologique, interféromètres à ondes atomiques (Miga), etc. Une nouvelle astronomie est donc née fin 2015, fondée non plus sur la réception de lumière, mais sur la détection d’ondes gravitationnelles, extrêmement pénétrantes, qui se caractérisent par une infime déformation de l’espace-temps. L’Académie des sciences se félicite de cette découverte spectaculaire et des avancées scientifiques qu’elle va engendrer.

*Michel Davier est coauteur de la publication de la collaboration LIGO/Virgo dans la revue Physical Review Letters : PRL 116, 061102
(2016)

**Christian Bordé, Laboratoire de physique des lasers et Syrte-Observatoire de Paris ; Catherine Bréchignac, Secrétaire
science, la technologie et l’innovation ; Yvonne Choquet-Bruhat,
professeur émérite à l’universite Pierre-et-Marie-Curie, Paris ;
Thibault Damour, Institut des hautes études scientifiques ; Michel
Davier, Laboratoire de l’Accélérateur Linéaire, IN2P3/CNRS et
Université Paris-Saclay

Paris, le 11 février 2016

Posted

• by Budgieye moderator

Merci, c_cld

Posted

• by c_cld

Wednesday, February 24, 2016 : At a hearing of the House Committee on Science, Space and Technology, Congressman Bill Foster , the only physicist in Congress (!) discusses gravitational waves.

https://youtu.be/NInj5FEBCvA

Full Committee Hearing - Unlocking the Secrets of the Universe: Gravitational Waves

Date: Wednesday, February 24, 2016 https://science.house.gov/legislation/hearings/full-committee-hearing-unlocking-secrets-universe-gravitational-waves

Posted

• Possible Light Flash from Black Hole Collision Spotted

Any particular region from the flash known yet?

Posted

• by c_cld

An improved analysis of GW150914 using a fully spin-precessing waveform model from The LIGO Scientific Collaboration, the Virgo Collaboration

This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) on September 14, 2015

we quote updated component masses of

$( m_1,\quad&space;m_2)&space;=&space;35^{+5}_{-3},\quad30^{+3}_{-4}&space;\quad&space;M_\odot$

(where errors correspond to 90% symmetric credible intervals).

one obtains parameters

$total\,mass\quad&space;M=m_1+m_2\quad&space;\Rightarrow&space;65\,\mathrm{M}_\odot&space;\\&space;\\reduced\,&space;mass\,&space;\mu\quad\mu^{-1}=m_1^{-1}+m_2^{-1}\quad&space;\Rightarrow&space;16.1538\,\mathrm{M}_\odot&space;\\\\symmetric\,&space;mass\,&space;ratio\quad&space;\nu=\mu/M\quad&space;\Rightarrow&space;0.24852&space;\\\\chirp\,mass\quad\mathcal{M}=(M^2\mu^3)^{1/5}\quad&space;\Rightarrow&space;28.1923\,\rm{M}_\odot$

$( m_1,\quad&space;m_2)&space;=&space;36^{+5}_{-4},\quad29^{+4}_{-4}&space;\quad&space;M_\odot$

Posted

• by c_cld

To get a general understanding of the order of magnitude of the signal picked by the detectors for the chirping binary black holes in the inspiral phase let us use the characteristics of the sources.

By the so-called "quadrupole formula" obtained by Albert Einstein in 1918, the leading order energy loss (per unit time) of a source of gravitational waves depends on the third time derivative of the moment of inertia tensor also known as the "quadrupole moment tensor".

Using this formula and assuming a circular binary black holes source at luminosity distance D_L (440Mpc), one finds the strain amplitude h of gravitational waves measured by LIGO as:

$h&space;=&space;4\frac{G}{c^2}\frac{\mathcal{M}}{\mathcal{D}_L}\left&space;(&space;\frac{G}{c^3}&space;\pi&space;f&space;\mathcal{M}&space;\right&space;)^{2/3}$

The expressions for the derivative of the frequency of GW and for the luminosity distance are:

$\dot{f}=\frac{96}{5}\frac{\pi^{8/3}}{c^5}f^{11/3}\left(G\mathcal{M}\right&space;)^{5/3}\quad;\quad\mathcal{D}_L=\frac{5}{96\pi^2}\frac{c}{h}\frac{\dot{f}}{f^3}$

Given GW150914 release data at https://losc.ligo.org/events/GW150914/
one gets the approximation analysis exercise with simple spreadsheet :

 time strain GW frequency GW wavelength second (h x 10^21) Hz km 0.26433 0.4852 36.08 8,308 0.28026 0.4971 37.42 8,012 0.29558 0.5100 38.89 7,709 0.31029 0.5246 40.57 7,389 0.32439 0.5412 42.51 7,053 0.33782 0.5604 44.79 6,693 0.35051 0.5825 47.47 6,316 0.36248 0.6085 50.69 5,915 0.37365 0.6396 54.62 5,489 0.38396 0.6782 59.63 5,027 0.39336 0.7273 66.23 4,527 0.40172 0.7926 75.34 3,979 0.40899 0.8819 88.43 3,390 0.41497 1.0045 107.49 2,789 0.41967 1.1503 131.74 2,276

Plotting the time-frequency allows to clearly see the "chirp" 😃

Posted

• by c_cld

(continued) Back-of-the-envelope calculation with excel sheet (to be checked)!

Gravitational waves (GW) power radiated from binary black holes (BH/BH) system for quasi-circular orbits (inspiral waveform) averaging over polarizations

$luminosity&space;\quad&space;\mathcal{L}_G_W=&space;-\frac{dE}{dt}=\frac{32}{5}\frac{G^{7/3}}{c^5}\left&space;(&space;\omega&space;\mathcal&space;{M}&space;\right&space;)^{10/3}$

GW150914 before merger

 time BH orbital frequency BHs separation BHs velocity luminosity GW luminosity GW second Hz km factor of c erg/s EM sun factor 0.26433 18.04 876 0.33 2.27E+54 5.93E+18 0.28026 18.71 855 0.34 2.56E+54 6.69E+18 0.29558 19.44 833 0.34 2.91E+54 7.61E+18 0.31029 20.29 810 0.34 3.35E+54 8.76E+18 0.32439 21.25 785 0.35 3.92E+54 1.02E+19 0.33782 22.40 758 0.36 4.67E+54 1.22E+19 0.35051 23.73 729 0.36 5.66E+54 1.48E+19 0.36248 25.34 698 0.37 7.05E+54 1.84E+19 0.37365 27.31 664 0.38 9.04E+54 2.36E+19 0.38396 29.82 626 0.39 1.21E+55 3.16E+19 0.39336 33.12 584 0.41 1.72E+55 4.49E+19 0.40172 37.67 536 0.42 2.64E+55 6.90E+19 0.40899 44.22 482 0.45 4.50E+55 1.18E+20 0.41497 53.75 423 0.48 8.63E+55 2.26E+20 0.41967 65.87 369 0.51 1.70E+56 4.44E+20

The estimated energy radiated in GWs from the sources in this inspiral segment is around 2.15×10^54 erg

i.e.

~2.15×10^47 J (joules)

~ 1.2 × relativistic mass-energy equivalent of a solar mass ( 1 M_sun c^2 )

~ 2200 × energy released from a supernova (~~ 1×10^44 J )

From reading publications by "LIGO Scientiﬁc Collaboration and Virgo Collaboration"
, the total energy emitted in gravitational waves for GW150914 during inspiral, merger and ringdown was of the order of 5 x 10^54 erg (~ 2.8 × relativistic mass-energy equivalent of a solar mass ( 1 M_sun c^2 ) )

(end of the orders of approximation)

Posted

• by c_cld

Demonstration of strain data for the inspiraling and merging BHs sources in event GW150914

courtesy Satya Mohapatra
"Gravitational Waves from Non-precessing Spinning Binary Black Hole Coalescence"
http://demonstrations.wolfram.com/GravitationalWavesFromNonPrecessingSpinningBinaryBlackHoleCo/
Wolfram Demonstrations Project

Posted

• by c_cld

LIGO Does It Again: A Second Robust Binary Black Hole Coalescence Observed

GW151226: A Second Confirmed Source of Gravitational Radiation

Astronomy Picture of the Day

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• by c_cld

The LIGO Scientiﬁc Collaboration and The Virgo Collaboration (15JUNE2016)

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• by c_cld

Posted

• by c_cld

Help @LIGO improve the search for gravitational waves - join the beta test of http://gravityspy.org with @the_zooniverse @gravityspyzoo

https://www.zooniverse.org/projects/zooniverse/gravity-spy

Posted

• by Budgieye moderator in response to c_cld's comment.

Amazing! Another gravitational wave discovery so soon.

Posted

• by ElisabethB moderator

Very exciting news ! 😄

Posted

• by c_cld

Demonstration of strain data for the inspiraling and merging BHs sources in event GW151226

courtesy Satya Mohapatra "Gravitational Waves from Non-precessing Spinning Binary Black Hole Coalescence" http://demonstrations.wolfram.com/GravitationalWavesFromNonPrecessingSpinningBinaryBlackHoleCo/ Wolfram Demonstrations Project

Posted

• by c_cld

Gravitational-wave signal observed by the LIGO Hanford detector buried in the noise and processed by matching with template waveform.

my plot using tutorial and data from https://losc.ligo.org/s/events/GW151226/LOSC_Event_tutorial_GW151226.html

Posted

• by c_cld

LSC News
UPDATE ON LIGO'S SECOND OBSERVING RUN

28 January 2017 -- The second Advanced LIGO run began on November 30,
2016 and is currently in progress. As of January 23 approximately 12 days of Hanford-Livingston coincident science data have been collected, with a scheduled break between December 22, 2016 and January 4, 2017...

So far, 2 event candidates, identified by online analysis using a
loose false-alarm-rate threshold of one per month, have been
identified and shared with astronomers who have signed memoranda of
understanding with LIGO and Virgo for observational followup. A
thorough investigation of the data and offline analysis are in
progress; results will be shared when available.

Posted

• by c_cld

UPDATE ON LIGO'S SECOND OBSERVING RUN

9 March 2017 -- The second Advanced LIGO run began on November 30,
2016 and is currently in progress. As of February 23 approximately 30
days of Hanford-Livingston coincident science data have been
collected, with a scheduled break between December 22, 2016 and
January 4, 2017. The average reach of the LIGO network for binary
merger events has been around 70 Mpc for 1.4+1.4 Msun, 300 Mpc for
10+10 Msun and 700 Mpc for 30+30 Msun mergers, with relative
variations in time of the order of 10%.

So far, 3 event candidates, identified by online analysis using a
loose false-alarm-rate threshold of one per month, have been
identified and shared with astronomers who have signed memoranda of
understanding with LIGO and Virgo for electromagnetic followup. A
thorough investigation of the data and offline analysis are in
progress; results will be shared when available.

Posted

• by c_cld

Principal gravitational wave source SCO X-1

Has LIGO run O2 made a detection of SCO X-1? ( a low-mass X-ray binary; the neutron star is roughly 1.4 solar masses, while the donor star is only 0.42 solar masses at 2.8 Kpc )

Mapping the gravitational wave sky

arXiv:1610.09391v2 Searches for continuous gravitational waves from Scorpius X-1 and XTE J1751-305 in LIGO's sixth science run from Grant Meadors et al. 28 Oct 2016 revised 23 Feb 2017

arXiv:1612.02030v4 Directional limits on persistent gravitational waves from Advanced LIGO's first observing run from The LIGO Scientific Collaboration, the Virgo Collaboration , 30 Jan 2017

Posted

• by c_cld

May 2017 update on LIGO's second observing run

3 May 2017 -- The second Advanced LIGO run began on November 30, 2016 and is currently in progress. As of April 23 approximately 67 days of Hanford-Livingston coincident science data have been collected. The average reach of the LIGO network for binary merger events has been around 70 Mpc for 1.4+1.4 Msun, 300 Mpc for 10+10 Msun and 700 Mpc for 30+30 Msun mergers, with relative variations in time of the order of 10%. As of April 23, 6 triggers have been identified by the online analysis, using a loose false-alarm-rate threshold of one per month, and shared with astronomers who have signed memoranda of understanding with LIGO and Virgo for electromagnetic followup. A thorough investigation of the data and offline analysis are in progress; results will be shared when available.

Posted

• by c_cld

The LIGO collaboration reports its third detection of gravitational waves coming from the merger of two black holes.

GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

B. P. Abbott et al. (LIGO Scientific and Virgo Collaboration)
Phys. Rev. Lett. 118, 221101 – Published 1 June 2017

Posted

• by Budgieye moderator

These events seem to occur several times a year. No wonder they detected a wave only two weeks after the machine was turned on.

Posted

• by c_cld

Demonstration of strain data for the inspiraling and merging BHs sources in event GW170104

courtesy Satya Mohapatra "Gravitational Waves from Non-precessing Spinning Binary Black Hole Coalescence" http://demonstrations.wolfram.com/GravitationalWavesFromNonPrecessingSpinningBinaryBlackHoleCo/ Wolfram Demonstrations Project

Posted

• by c_cld

Rumours swell over new kind of gravitational-wave sighting Author:
Davide Castelvecchi
Publication:
Nature News
Publisher:
Nature Publishing Group
Date:
Aug 24, 2017

Field NGC4993 ra, dec 197.448625 -23.384028 z ~0.0093 , is 40.0 Mpc or 0.130 Gly

HST proposal searches

Rapid ToO observations of the first gravitational wave counterparts HST Proposal 14804 Andrew Levan The University of Warwick; Target: ra, dec 13 09 48.080 -23 22 53.20

Identify the signature of neutron star mergers through rapid Chandra/Hubble observations of a short GRB HST Proposal 14850 Eleonora Troja University of Maryland; Target ra, dec 13 09 48.090 -23 22 53.35

Verifying a candidate counterpart to gravitational waves HST Proposal 15346 Mansi Kasliwal California Institute of Technology; Target ra, dec 13 09 48.089 -23 22 53.35

UV Spectroscopy of GRB170817A HST Proposal 15382 Matt Nicholl Harvard University; Target BNS-MERGER ra, dec 13 09 48.090 -23 22 53.35

Chandra observation : ObsDate
2017-08-19T17:28:27s Target SGRB170817A

TOO target of opportunity, Category of the observed target BH AND NS BINARIES

Posted

• by c_cld

HST Observation on 2017-04-28 03:40:
Schedule Gap Pilot
HST Proposal 14840 Andrea Bellini Space Telescope Science Institute

NGC4993 shows Dust Dust ... (post merger? )

Posted

• by c_cld

Second Chandra Observation scheduled for GRB170817A in ( NGC4993 RA: 13 09 47.71, Dec: -23 23 01.79 ) (Search )

Proposal Title: Bringing Gravitational Wave Astronomy to Light: Chandra X-ray Localization of LIGO-Virgo GW Sources

Proposal Number: 18400410

Principal Investigator: Daryl Haggard

``````| Obs ID | Instrument | Grating | Appr Exp | Target Name | PI Name | RA          | DEC          | Status    | Start Date    | Proposal | Type | Obs Cycle | Science Category   |
|--------|------------|---------|----------|-------------|---------|-------------|--------------|-----------|---------------|----------|------|-----------|--------------------|
| 18988  | ACIS-S     | NONE    | 50       | GRB170817A  | Haggard | 13 09 48.27 | -23 23 04.30 | scheduled | 9/2/2017 4:29 | 18400410 | TOO  | 18        | BH AND NS BINARIES |``````

Posted

• by c_cld

GW170814: A THREE-DETECTOR OBSERVATION OF GRAVITATIONAL WAVES FROM A BINARY BLACK HOLE COALESCENCE

Posted

• by c_cld

Top row: Signal-to-noise ratio as a function of time. The peaks occur at different times in different detectors because gravitational waves propagate at the finite speed of light; this causes the signal to reach the detectors at different times. GW170814 arrived first in LIGO-Livingston, then 8 ms later in LIGO-Hanford and 6 ms after that in Virgo. Middle row: Time-frequency representation of the strain data. The brighter a given pixel in any of the three 2D-maps, the larger the signal at this particular time and frequency with respect to the expected noise level. Note the characteristic "chirp" pattern of increasing frequency with time. Bottom row: Strain time series with the best waveforms selected by the matched filtering (black solid curves) and unmodeled search methods (gray bands) superimposed.

Posted

• by c_cld

More expected announcements of results to be confirmed at International Astronomical Union 2017 Symposium

This symposium will bring to light the latest results available in gravitational-wave astronomy, progress in multi-messenger astronomy, and the inferences that can be made from joint observations, to open a new window to the cosmos.

Gravitational Wave Astrophysics

Early Results from GW Searches and Electromagnetic Counterparts
Monday, October 16 – Thursday, October 19, 2017
Crowne Plaza, Baton Rouge, Louisiana

Posted

• by c_cld

http://hubblesite.org/news_release/news/2017-41

Compass Image for Gravitational Wave Source in NGC 4993

Posted

• by Budgieye moderator in response to c_cld's comment.

Amazing information thank you for posting. I will wait for the spectrum of the colliding neutron stars!

Posted

• by c_cld

VLT/MUSE image of the galaxy NGC 4993 and associated kilonova

RA: 13 9 47.78
Dec: -23° 22' 57.04"
Field of view: 0.91 x 0.85 arcminutes
Orientation: North is -0.0° left of vertical

This image from the MUSE instrument on ESO’s Very Large Telescope at the Paranal Observatory in Chile shows the galaxy NGC 4993, about 130 million light-years from Earth. The galaxy is not itself unusual, but it contains something never before witnessed, the aftermath of the explosion of a pair of merging neutron stars, a rare event called a kilonova (seen just above and slightly to the left of the centre of the galaxy). This merger also produced gravitational waves and gamma rays, both of which were detected by LIGO-Virgo and Fermi/INTEGRAL respectively. By also creating a spectrum for each part of the object MUSE allows the emission from glowing gas to be seen, which appears in red here and reveals a surprising spiral structure.

Credit:
ESO/J.D. Lyman, A.J. Levan, N.R. Tanvir

Posted

• by Budgieye moderator in response to c_cld's comment.

Surely this emission nebula has been here long before the kilonova erupted?

EDIT ooops, image is of the center of the galaxy? confusing.

Posted

• by c_cld

Kilonova AT 2017gfo

the transient was R.A. (2000) = 13:09:48.09, decl.(2000) = −23:22:53.3, approximately 10″ from the center of the S0 galaxy NGC 4993

https://wis-tns.weizmann.ac.il/object/2017gfo

Posted

• From MUSE imaging the "red gas" sits along the dust lanes of S0 NGC4993 as it's shown in

The science paper by A.J. Levan et al. (Astrophysical Journal Letters)

Figure 1. Imaging of the host galaxy of GW170817 with HST. The left panel shows the galaxy observed in the IR with F110W and F160W, where the counterpart is marked with a circle. The top right panel shows the zoomed-in region observed with WFC3/UVIS, demonstrated the presence of strong dust lanes in the inner regions. The bottom right panel shows the same image, but with the MUSE contours in the [N ii] line superimposed, showing the strong spiral features that only appear in the emission lines. Some of these features appear to trace the dust lanes.

Posted

• by c_cld

GW170608: another binary black hole merger

GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence arXiv:1711.05578 (Submitted on 15 Nov 2017)

On June 8, 2017 at 02:01:16.49 UTC, a gravitational-wave signal from the merger of two stellar-mass black holes was observed by the two Advanced LIGO detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses \$12^{+7}{-2},M\odot\$ and \$7^{+2}{-2},M\odot\$ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through gravitational waves with electromagnetic observations. The source's luminosity distance is 340+140−140 Mpc, corresponding to redshift 0.07+0.03−0.03. We verify that the signal waveform is consistent with the predictions of general relativity.

Posted

• by c_cld

Black holes gravitational waves events

entropy-increasing process

estimates

``````+-----------+--------+--------+--------------+------+------------------+
| GW event  | Mass 1 | Mass 2 | Mass remnant | Spin | entropy increase |
+-----------+--------+--------+--------------+------+------------------+
| GW150914  | 35.4   | 29.8   | 62.2         | 0.68 | 1.57             |
+-----------+--------+--------+--------------+------+------------------+
| LVT151012 | 23     | 13     | 35           | 0.66 | 1.54             |
+-----------+--------+--------+--------------+------+------------------+
| GW151226  | 14.2   | 7.5    | 20.8         | 0.74 | 1.40             |
+-----------+--------+--------+--------------+------+------------------+
| GW170104  | 31.2   | 19.4   | 48.7         | 0.64 | 1.55             |
+-----------+--------+--------+--------------+------+------------------+
| GW170608  | 12     | 7      | 18           | 0.69 | 1.45             |
+-----------+--------+--------+--------------+------+------------------+
| GW170814  | 30.5   | 25.3   | 53.2         | 0.7  | 1.54             |
+-----------+--------+--------+--------------+------+------------------+
``````

The entropy increase is the ratio of the event horizon area of the final black hole to the sum of the event horizon areas of the binary components

 My calculated entropy increase is a numerical application of "Bekenstein-Hawking entropy" article

Assuming the two progenitor black holes to be Schwarzschild black hole,

$r_h=2GM/c^2$

and area given by

$4\pi r_h^2$

The total "Schwarzschild" area is

$A_{Sch1}+ A_{Sch2}= 16 \pi (G/c^2)^2 (M^2_1 + M^2_2)$

The end product of the coalescence is a Kerr black hole, which is fully described by its mass M and spin J.

The horizon lies at the fixed radial coordinate

$r=r_h\equiv GM/c^2+ \sqrt{(GM/c^2)^2-(J/Mc)^2}$

The horizon area is given by

$A_{Kerr}= 4\pi(r_h^2 +(J/Mc)^2)$

Therefore the increase factor of entropy is

$A_{Kerr}/(A_{Sch1}+ A_{Sch2 })= (r_h^2+ (J/Mc)^2)/\left ( (2 G/c^2)^2 (M^2_1+ M^2_2)\right )$

which is tabulated above for the known GW events where we used

$Spin=Jc/GM^2$

as dimensionless Spin given in factsheets published.

Uncertanties propagation could be done to confirm the increase order of magnitude.

(to be reviewed by curator/scholar)

Since the approximate value of increases are curiously close and tantalizingly simple, one wonders this is accidental or quite sensible?

Posted

• by c_cld

Cross-refers to Observational tests of the black hole area increase law arXiv:1711.09073v1 [gr-qc] 24 Nov 2017 from Miriam Cabero, Collin D. Capano, Ofek Fischer-Birnholtz, et al.

The black hole area theorem implies that when two black holes merge, the area of the final black hole should be greater than the sum of the areas of the two original black holes. We examine how this prediction can be tested with gravitational-wave observations of binary black holes. By separately fitting the early inspiral and final ringdown phases, we calculate the posterior distributions for the masses and spins of the two initial and the final black holes. This yields posterior distributions for the change in the area and thus a statistical test of the validity of the area increase law. We illustrate this method with a GW150914-like binary black hole waveform calculated using numerical relativity and detector sensitivities representative of both the first observational run and the design configuration of Advanced LIGO. We find that the area theorem could be confirmed to ∼66% confidence with current sensitivity, improving to ∼97% when Advanced LIGO reaches design sensitivity. An important ingredient in our test is a method of estimating when the post-merger signal is well-fit by a damped sinusoid ringdown waveform.

Test of the Second Law of Black Hole Thermodynamics with the LIGO event GW150914 Unnikrishnan. C. S. , (Dated: 11 February 2016: Tribute to J. D. Bekenstein (1947-2015))

Abstract
The recent LIGO discovery of the binary black holes merging and forming a single Kerr black hole provides the first and unique opportunity to test the black hole area-entropy theorem or the second law of black hole thermodynamics. We discuss the test of the entropy law using the mass and spin estimates from the LIGO event GW150914. Because both the initial and final states consist only of black holes with high entropy and coherent gravitational waves with very low entropy, the test is essentially geometrical and ideal. However, the precision and the test itself are limited by interdependencies and errors in parameter estimation. Future studies on similar BBH events are critical precision tests of black hole area-entropy theorem

Posted

• by c_cld

full results of advanced-detector observing runs (O1 and O2) arXiv:1811.12907v1 [astro-ph.HE] 30 Nov 2018

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

update on Bekenstein-Hawking entropy quantities

``````+----------+--------+--------+--------------+------+------------------+------------+
| GW event | Mass 1 | Mass 2 | Mass remnant | Spin | entropy increase | efficiency |
+----------+--------+--------+--------------+------+------------------+------------+
| GW150914 | 35.6   | 30.6   | 63.1         | 0.69 | 1.56             | 4.68%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW151012 | 23.3   | 13.6   | 35.7         | 0.67 | 1.53             | 3.25%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW151226 | 13.7   | 7.7    | 20.5         | 0.74 | 1.42             | 4.21%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170104 | 31     | 20.1   | 49.1         | 0.66 | 1.55             | 3.91%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170608 | 10.9   | 7.6    | 17.8         | 0.69 | 1.55             | 3.78%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170729 | 50.6   | 34.3   | 80.3         | 0.81 | 1.37             | 5.42%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170809 | 35.2   | 23.8   | 56.4         | 0.7  | 1.51             | 4.41%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170814 | 30.7   | 25.3   | 53.4         | 0.72 | 1.53             | 4.64%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170818 | 35.5   | 26.8   | 59.8         | 0.67 | 1.57             | 4.01%      |
+----------+--------+--------+--------------+------+------------------+------------+
| GW170823 | 39.6   | 29.4   | 65.6         | 0.71 | 1.51             | 4.93%      |
+----------+--------+--------+--------------+------+------------------+------------+``````

Posted

• by c_cld

Twin LIGO/Virgo Detections of a Viable Gravitationally-Lensed Black Hole Merger arXiv:1901.03190 From Tom Broadhurst, Jose M. Diego, George F. Smoot III

(Submitted on 10 Jan 2019)

We identify a binary black hole (BBH) merger that appears to be
multiply lensed by an intervening galaxy. The LIGO/Virgo events
GW170809 and GW170814 have indistinguishable waveforms separated by 5
days, and overlap on the sky within the 90% credible region. Their
strain amplitudes are also similar, implying a modest relative
magnification ratio, as expected for a pair of lensed gravitational
waves. The phase of the two events is also consistent with being the
same, adding more evidence in support of both events originating from
the same BBH merger. The difference in the published inferred
distances of each event can then be interpreted as following from
their different magnifications. The observed chirp masses of both
events are also similar, as expected for a pair of lensed events, with
a common detected value of 29.1+1.3−1.0M⊙, lying at the peak of the
observed distribution of chirp masses. We infer this case is a
prototypical example of a lensed event that supports our lensing
prediction \cite{Broadhurst2018} according to which, cosmologically
distant, magnified BBH comprise most of the LIGO/Virgo events with
chirp masses enhanced above ≃15M⊙ by the cosmological expansion. From
our predictions we estimate an intrinsic, unlensed, chirp mass of
≃10−12M⊙, with a source redshift in the range 0.9 < z < 2.5. We also
outline a joint analysis over all baseline permutations that can
stringently test our lensing interpretation of these two events. More
generally, lensed events effectively multiply the number of baseline
permutations and motivates the use of more interferometers for round
the clock coverage of all repeat events of a given source, in order to
maximise the orbital details and sky localization of lensed BBH
sources.

Posted