@article{52b5aaffcdda4a0caa3c905606caf2d1,
title = "Swift-XRT follow-up of gravitational wave triggers during the third aLIGO/Virgo observing run",
abstract = "The Neil Gehrels Swift Observatory followed up 18 gravitational wave (GW) triggers from the LIGO/Virgo collaboration during the O3 observing run in 2019/2020, performing approximately 6500 pointings in total. Of these events, four were finally classified (if real) as binary black hole (BH) triggers, six as binary neutron star (NS) events, two each of NSBH and Mass Gap triggers, one an unmodelled (Burst) trigger, and the remaining three were subsequently retracted. Thus far, four of these O3 triggers have been formally confirmed as real gravitational wave events. While no likely electromagnetic counterparts to any of these GW events have been identified in the X-ray data (to an average upper limit of 3.60 × 10−12 erg cm−2 s−1 over 0.3-10 keV), or at other wavelengths, we present a summary of all the Swift-XRT observations performed during O3, together with typical upper limits for each trigger observed. The majority of X-ray sources detected during O3 were previously uncatalogued; while some of these will be new (transient) sources, others are simply too faint to have been detected by earlier survey missions such as ROSAT. The all-sky survey currently being performed by eROSITA will be a very useful comparison for future observing runs, reducing the number of apparent candidate X-ray counterparts by up to 95 per cent.",
author = "Page, {K. L.} and Evans, {P. A.} and A. Tohuvavohu and Kennea, {J. A.} and Klingler, {N. J.} and Cenko, {S. B.} and Oates, {S. R.} and E. Ambrosi and Barthelmy, {S. D.} and Beardmore, {A. P.} and Bernardini, {M. G.} and Breeveld, {A. A.} and Brown, {P. J.} and Burrows, {D. N.} and S. Campana and R. Caputo and G. Cusumano and A. D'A{\`i} and P. D'Avanzo and V. D'Elia and {de Pasquale}, M. and Emery, {S. W.K.} and P. Giommi and C. Gronwall and Hartmann, {D. H.} and Krimm, {H. A.} and Kuin, {N. P.M.} and Malesani, {D. B.} and Marshall, {F. E.} and A. Melandri and Nousek, {J. A.} and O'Brien, {P. T.} and Osborne, {J. P.} and C. Pagani and Page, {M. J.} and Palmer, {D. M.} and M. Perri and Racusin, {J. L.} and T. Sakamoto and B. Sbarufatti and Schlieder, {J. E.} and Siegel, {M. H.} and G. Tagliaferri and E. Troja",
note = "Funding Information: KLP, PAE, APB, AAB, NPMK, JPO, CP, and MJP acknowledge funding from the UK Space Agency. NJK acknowledges support from NASA Grant 80NSSC19K0408. AD acknowledges financial contribution from the agreement ASI-INAF n.2017-14-H.0, while EA, MGB, SC, GC, AD, AM, and GT acknowledge funding from the Italian Space Agency, contract ASI/INAF n. I/004/11/4. This work is also partially supported by a grant from the Italian Ministry of Foreign Affairs and International Cooperation Nr. MAE0065741 (AD), and by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) KAKENHI Grant Numbers 17H06357 and 17H06362 (TS). DBM acknowledges research grant 19054 from VILLUM FONDEN. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. We thank Dr Gavin Lamb for useful discussions. Publisher Copyright: {\textcopyright} 2020 The Author(s)",
year = "2020",
month = dec,
day = "1",
doi = "10.1093/mnras/staa3032",
language = "English (US)",
volume = "499",
pages = "3459--3480",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "3",
}