Erratum: Swift follow-up of gravitational wave triggers: Results from the first aLIGO run and optimisation for the future (Monthly Notices of the Royal Astronomical Society (2016) 462 (1591) DOI: 10.1093/mnras/stw1746)

P. A. Evans, Jamie A. Kennea, D. M. Palmer, M. Bilicki, J. P. Osborne, P. T. O'Brien, N. R. Tanvir, A. Y. Lien, S. D. Barthelmy, David Nelson Burrows, S. Campana, S. B. Cenko, V. D'Elia, N. Gehrels, F. E. Marshall, K. L. Page, M. Perri, Boris Sbarufatti, Michael Hiram Siegel, G. TagliaferriE. Troja

Research output: Contribution to journalComment/debate

Abstract

There was an error in equation (7) of Evans et al. (2016). That equation contains the normalising term N P , which is the total number of pixels in the gravitational wave (GW) localisation probability map. The paper states: “N P is the number of pixels in the map, and L tot is the total catalogued galaxy luminosity within the GW volume, so L L g tot NP gives the ratio of the actual luminosity in pixel p compared to that expected if the galaxies were homogeniously distributed on the sky, i.e. the relative probability of this pixel hosting a merger event compared to any other pixel.”. While this is true, it results in an incorrect overall normalization of the probability that the GW event is in a known galaxy (= P gal = p (P gal,p )) compared to not being in such a galaxy (= P nogal = p (P nogal,p ); P refers to the total probability, P p is the probability in pixel p). The correct formulation should result in P gal = C, ¯ P nogal = 1 − C ¯ , where C ¯ is the mean completeness of the galaxy catalogue employed at the distance of the GW event. Since P gal is simply the sum over all pixels, p, of equation (7) in Evans et al. (2016), one should find: (Farmula Presented) (Figure Presented) The impact of this error is modest. The incorrect formulation resulted in the over-emphasis of catalogued galaxies within the GW error region. The only GWevent to date for which this may have had an impact was GW170817 (e.g. Abbott et al. 2017), for which the GWmerger was in a catalogued galaxy, thus this error if anything aided the search. Fig. 1 demonstrates quantitatively the impact of the error. Here we show the cumulative probability in the galaxy-convolved skymap as a function of area enclosed (summing over pixels in decreasing probability order). The original equation (7) shown in black clearly overestimates the enclosed probability as a function of area; the discrepency being worse as the fractional probability enclosed becomes high.

Original languageEnglish (US)
Pages (from-to)2362-2363
Number of pages2
JournalMonthly Notices of the Royal Astronomical Society
Volume484
Issue number2
DOIs
StatePublished - Jan 1 2019

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gravitational waves
actuators
pixel
pixels
galaxies
optimization
luminosity
notice
formulations
normalizing
completeness
merger
catalogs
sky

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Evans, P. A. ; Kennea, Jamie A. ; Palmer, D. M. ; Bilicki, M. ; Osborne, J. P. ; O'Brien, P. T. ; Tanvir, N. R. ; Lien, A. Y. ; Barthelmy, S. D. ; Burrows, David Nelson ; Campana, S. ; Cenko, S. B. ; D'Elia, V. ; Gehrels, N. ; Marshall, F. E. ; Page, K. L. ; Perri, M. ; Sbarufatti, Boris ; Siegel, Michael Hiram ; Tagliaferri, G. ; Troja, E. / Erratum : Swift follow-up of gravitational wave triggers: Results from the first aLIGO run and optimisation for the future (Monthly Notices of the Royal Astronomical Society (2016) 462 (1591) DOI: 10.1093/mnras/stw1746). In: Monthly Notices of the Royal Astronomical Society. 2019 ; Vol. 484, No. 2. pp. 2362-2363.
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title = "Erratum: Swift follow-up of gravitational wave triggers: Results from the first aLIGO run and optimisation for the future (Monthly Notices of the Royal Astronomical Society (2016) 462 (1591) DOI: 10.1093/mnras/stw1746)",
abstract = "There was an error in equation (7) of Evans et al. (2016). That equation contains the normalising term N P , which is the total number of pixels in the gravitational wave (GW) localisation probability map. The paper states: “N P is the number of pixels in the map, and L tot is the total catalogued galaxy luminosity within the GW volume, so L L g tot NP gives the ratio of the actual luminosity in pixel p compared to that expected if the galaxies were homogeniously distributed on the sky, i.e. the relative probability of this pixel hosting a merger event compared to any other pixel.”. While this is true, it results in an incorrect overall normalization of the probability that the GW event is in a known galaxy (= P gal = p (P gal,p )) compared to not being in such a galaxy (= P nogal = p (P nogal,p ); P refers to the total probability, P p is the probability in pixel p). The correct formulation should result in P gal = C, ¯ P nogal = 1 − C ¯ , where C ¯ is the mean completeness of the galaxy catalogue employed at the distance of the GW event. Since P gal is simply the sum over all pixels, p, of equation (7) in Evans et al. (2016), one should find: (Farmula Presented) (Figure Presented) The impact of this error is modest. The incorrect formulation resulted in the over-emphasis of catalogued galaxies within the GW error region. The only GWevent to date for which this may have had an impact was GW170817 (e.g. Abbott et al. 2017), for which the GWmerger was in a catalogued galaxy, thus this error if anything aided the search. Fig. 1 demonstrates quantitatively the impact of the error. Here we show the cumulative probability in the galaxy-convolved skymap as a function of area enclosed (summing over pixels in decreasing probability order). The original equation (7) shown in black clearly overestimates the enclosed probability as a function of area; the discrepency being worse as the fractional probability enclosed becomes high.",
author = "Evans, {P. A.} and Kennea, {Jamie A.} and Palmer, {D. M.} and M. Bilicki and Osborne, {J. P.} and O'Brien, {P. T.} and Tanvir, {N. R.} and Lien, {A. Y.} and Barthelmy, {S. D.} and Burrows, {David Nelson} and S. Campana and Cenko, {S. B.} and V. D'Elia and N. Gehrels and Marshall, {F. E.} and Page, {K. L.} and M. Perri and Boris Sbarufatti and Siegel, {Michael Hiram} and G. Tagliaferri and E. Troja",
year = "2019",
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doi = "10.1093/mnras/stz113",
language = "English (US)",
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pages = "2362--2363",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
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Evans, PA, Kennea, JA, Palmer, DM, Bilicki, M, Osborne, JP, O'Brien, PT, Tanvir, NR, Lien, AY, Barthelmy, SD, Burrows, DN, Campana, S, Cenko, SB, D'Elia, V, Gehrels, N, Marshall, FE, Page, KL, Perri, M, Sbarufatti, B, Siegel, MH, Tagliaferri, G & Troja, E 2019, 'Erratum: Swift follow-up of gravitational wave triggers: Results from the first aLIGO run and optimisation for the future (Monthly Notices of the Royal Astronomical Society (2016) 462 (1591) DOI: 10.1093/mnras/stw1746)', Monthly Notices of the Royal Astronomical Society, vol. 484, no. 2, pp. 2362-2363. https://doi.org/10.1093/mnras/stz113

Erratum : Swift follow-up of gravitational wave triggers: Results from the first aLIGO run and optimisation for the future (Monthly Notices of the Royal Astronomical Society (2016) 462 (1591) DOI: 10.1093/mnras/stw1746). / Evans, P. A.; Kennea, Jamie A.; Palmer, D. M.; Bilicki, M.; Osborne, J. P.; O'Brien, P. T.; Tanvir, N. R.; Lien, A. Y.; Barthelmy, S. D.; Burrows, David Nelson; Campana, S.; Cenko, S. B.; D'Elia, V.; Gehrels, N.; Marshall, F. E.; Page, K. L.; Perri, M.; Sbarufatti, Boris; Siegel, Michael Hiram; Tagliaferri, G.; Troja, E.

In: Monthly Notices of the Royal Astronomical Society, Vol. 484, No. 2, 01.01.2019, p. 2362-2363.

Research output: Contribution to journalComment/debate

TY - JOUR

T1 - Erratum

T2 - Swift follow-up of gravitational wave triggers: Results from the first aLIGO run and optimisation for the future (Monthly Notices of the Royal Astronomical Society (2016) 462 (1591) DOI: 10.1093/mnras/stw1746)

AU - Evans, P. A.

AU - Kennea, Jamie A.

AU - Palmer, D. M.

AU - Bilicki, M.

AU - Osborne, J. P.

AU - O'Brien, P. T.

AU - Tanvir, N. R.

AU - Lien, A. Y.

AU - Barthelmy, S. D.

AU - Burrows, David Nelson

AU - Campana, S.

AU - Cenko, S. B.

AU - D'Elia, V.

AU - Gehrels, N.

AU - Marshall, F. E.

AU - Page, K. L.

AU - Perri, M.

AU - Sbarufatti, Boris

AU - Siegel, Michael Hiram

AU - Tagliaferri, G.

AU - Troja, E.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - There was an error in equation (7) of Evans et al. (2016). That equation contains the normalising term N P , which is the total number of pixels in the gravitational wave (GW) localisation probability map. The paper states: “N P is the number of pixels in the map, and L tot is the total catalogued galaxy luminosity within the GW volume, so L L g tot NP gives the ratio of the actual luminosity in pixel p compared to that expected if the galaxies were homogeniously distributed on the sky, i.e. the relative probability of this pixel hosting a merger event compared to any other pixel.”. While this is true, it results in an incorrect overall normalization of the probability that the GW event is in a known galaxy (= P gal = p (P gal,p )) compared to not being in such a galaxy (= P nogal = p (P nogal,p ); P refers to the total probability, P p is the probability in pixel p). The correct formulation should result in P gal = C, ¯ P nogal = 1 − C ¯ , where C ¯ is the mean completeness of the galaxy catalogue employed at the distance of the GW event. Since P gal is simply the sum over all pixels, p, of equation (7) in Evans et al. (2016), one should find: (Farmula Presented) (Figure Presented) The impact of this error is modest. The incorrect formulation resulted in the over-emphasis of catalogued galaxies within the GW error region. The only GWevent to date for which this may have had an impact was GW170817 (e.g. Abbott et al. 2017), for which the GWmerger was in a catalogued galaxy, thus this error if anything aided the search. Fig. 1 demonstrates quantitatively the impact of the error. Here we show the cumulative probability in the galaxy-convolved skymap as a function of area enclosed (summing over pixels in decreasing probability order). The original equation (7) shown in black clearly overestimates the enclosed probability as a function of area; the discrepency being worse as the fractional probability enclosed becomes high.

AB - There was an error in equation (7) of Evans et al. (2016). That equation contains the normalising term N P , which is the total number of pixels in the gravitational wave (GW) localisation probability map. The paper states: “N P is the number of pixels in the map, and L tot is the total catalogued galaxy luminosity within the GW volume, so L L g tot NP gives the ratio of the actual luminosity in pixel p compared to that expected if the galaxies were homogeniously distributed on the sky, i.e. the relative probability of this pixel hosting a merger event compared to any other pixel.”. While this is true, it results in an incorrect overall normalization of the probability that the GW event is in a known galaxy (= P gal = p (P gal,p )) compared to not being in such a galaxy (= P nogal = p (P nogal,p ); P refers to the total probability, P p is the probability in pixel p). The correct formulation should result in P gal = C, ¯ P nogal = 1 − C ¯ , where C ¯ is the mean completeness of the galaxy catalogue employed at the distance of the GW event. Since P gal is simply the sum over all pixels, p, of equation (7) in Evans et al. (2016), one should find: (Farmula Presented) (Figure Presented) The impact of this error is modest. The incorrect formulation resulted in the over-emphasis of catalogued galaxies within the GW error region. The only GWevent to date for which this may have had an impact was GW170817 (e.g. Abbott et al. 2017), for which the GWmerger was in a catalogued galaxy, thus this error if anything aided the search. Fig. 1 demonstrates quantitatively the impact of the error. Here we show the cumulative probability in the galaxy-convolved skymap as a function of area enclosed (summing over pixels in decreasing probability order). The original equation (7) shown in black clearly overestimates the enclosed probability as a function of area; the discrepency being worse as the fractional probability enclosed becomes high.

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