PoS(ICRC2019)698 http://pos.sissa.it/ † ∗ [email protected] Speaker. for collaboration list see PoS(ICRC2019)1177 Fast radio bursts (FRBs) areoriginating bright, from unresolved, outside millisecond-duration flashes ofknown, of the radio but Milky emission their Way. hightreme, luminosity, The high-energy, high astrophysical origin process. dispersion of The measure these majorityevents and of mysterious which short FRBs would outbursts have duration require been is requires a discovered as un- chancevations. an single coincidence ex- for However, contemporaneous two multiwavelength have obser- FRB 180814.J0422+73. been These observed repeating to FRBs have repeat: allowedber for of targeted FRB different 121102 observations instruments, by including and a VERITAS. the We num- gram present and recently the the VERITAS detected results FRB of observing these pro- observations. † ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 36th International Cosmic Ray Conference -ICRC2019- July 24th - August 1st, 2019 Madison, WI, U.S.A. Department of Physics and Astronomy andDelaware, the Newark, Bartol DE Research 19713. Institute, University of E-mail: for the VERITAS Collaboration Jamie Holder Ryan S. Lynch PO Box 2, Green Bank, WV 24944 VERITAS Observations of Fast Radio Bursts PoS(ICRC2019)698 ]. Digiti- 16 Jamie Holder , ]. The discov- 15 11 ]. In this contribution, we ]. In this case, a rapidly 6 12 10 billion times larger than ∼ ; five orders of magnitude greater 2 m ]. Imaging atmospheric Cherenkov 8 5 , 7 10 ]. The telescopes are located on the cor- ∼ , and with multi-telescope arrays equipped 14 2 100 m. Each steerable telescope is equipped ] has been extensively reviewed recently in , 1 ∼ 13 1 ]. For FRB 121102, radio polarization measure- 100 m telescopes in the world. Their spatial resolution is 5 > optical ]). 10 ] and FRB 180814.J0422+73 [ , 4 9 ]. These millisecond-duration events occur at the rate of thousands per day and are now 3 The discovery of prompt counterparts at any wavelength would strongly discriminate between VERITAS is an array of four, 12 m diameter atmospheric Cherenkov telescopes located at the In searching for optical or gamma-ray counterparts to FRBs with IACTs, the difficulty is know- The phenomenon of fast radio bursts (FRBs) [ . For observations in the gamma-ray band, images of the Cherenkov light from cosmic ray and ◦ ] and [ 5 . 2 zation of the AC-coupled photomultiplier tube signals occurs at 500 megasamples-per-second, for with fast photosensors, theysources are (e.g. ideal [ instruments for optical photometry of very rapid transient Galactic pulsars. Theent nature properties of in the the sources radio(as observations, is discussed and unclear; in many the the different aforementioned emission burstsFRB reviews). models 121102 show have Two [ a FRB been sources proposed wide have range now of been shown differ- to repeat: than space-based detectors. For millisecond-timescale phenomena, theyfree. are essentially In background addition, IACTs arevery the poor, largest by the standardsfew of arc optical minutes; astronomy, however, with with typical mirror areas optical point spread functions of a ners of an approximate square, with side lengths of the various possible origin scenarios andSpace-based allow searches an for estimate high of the energyments bolometric FRB on luminosity counterparts board of have the FRBs. been Fermi performed Gamma-ray using Space both Telescope [ instru- Fred Lawrence Whipple Observatory in Arizona [ rotating young magnetar, or a neutronprovide a star plausible in explanation, the but immediate alternative environment models of still a exist. massive black hole, telescopes (IACTs) are uniquely suited to conductergies, such IACTs provide searches an from instantaneous the effective ground. area of At GeV-TeV en- ing when and where to look.the telescopes The to field the of correct view location oflocations takes seconds with IACTs or is IACTs were minutes. a therefore Until few limited recently, degreesery to observations in of of the diameter repeating FRB search FRBs and for allows slewing afterglow contemporaneous emission monitoringtelescopes, [ of a FRB technique locations which with has IACTs and alreadyemission radio been from exploited five to bursts place of limits FRB 121102 onreport with gamma-ray on the and the MAGIC optical status telescopes of [ searches forIACT optical array. and high energy emission from FRBs with the VERITAS 2. VERITAS with a 499-pixel photomultiplier tube camera,3 covering a circular field-of-view withgamma-ray a initiated diameter air of showers are recorded and processed using standard tools [ known to be extragalactic in origin, implying radio flux densities ments indicate an extreme magneto-ionic environment at the source [ VERITAS Observations of FRBs 1. Introduction [ PoS(ICRC2019)698 tool ] but, 17 Jamie Holder ]. While some of 18 5625 MHz and coherently . gamma-ray selection cuts us- single_pulse_search.py moderate . The data were searched for bright pulses and 3 − using the soft 3 2 − is the number of channels read out, and has a sensitivity n s with a frequency resolution of 1 µ 24 . Hz, where n / ]. No radio bursts have been reported during the VERITAS observations. 25 800 , software suite. Spectrograms were created and inspected for all candidates 1 PRESTO https://www.cv.nrao.edu/~sransom/presto/ No evidence for steady gamma-ray emission has been seen from either of the repeating burst Results of a search for steady gamma-ray emission from the location of FRB 121102 with 10.8 The requirements for millisecond-timescale optical photometry are significantly different to VERITAS observations of the more recently identified repeating FRB, FRB 180814.J0422+73, 1 ing boosted decision trees trained on gamma-ray simulations and real cosmic ray background locations. Two analyses were performed, with 4. Results 4.1 Gamma-ray search hours of VERITAS observations taken over 2016-2017 have been reported in [ roughly equivalent to a limiting magnitude of 11 for an astronomical B-filter. 3. Observations those of gamma-ray observations, and soparallel a to specialized normal data Cherenkov acquisition operations. chain Details is are used given which elsewhere in is these fully proceedings [ VERITAS Observations of FRBs Cherenkov images which exceed thewindow array around trigger the thresholds. time of The the readout trigger. is restricted to a 32 ns briefly, the DC-coupled photomultiplier tube voltageslogger are recorded (DATAQ instruments using DI-710-ELS) a on commercial 14-bitsamples up data at to a 16 rate channels of 4 for each telescope. The system these exposures were coincident withthe Arecibo overlapping observations, observations. no radio Additional burstsber VERITAS were 2017 observations reported (MJD of during 58082) FRB were 121102 made(GBT). on in Data 25 were coincidence recorded Novem- with using the the Robertwith Green C. Bank a Byrd Ultimate Green bandwidth Pulsar Bank Processing of Telescope Instrumentspectra (GUPPI) 800 were MHz recorded every centered 10 ondedispersed a at a radio dispersion frequencyfrom measure of dispersion of 2000 measures 560 MHz. of pc 527 cm from to Full-polarization the 587 pc cm with signal-to-noise ratio >trial 7 sources in of order radio frequency to interference.MJD differentiate During 58082.413 between 115 minutes to astrophysical of 58082.495), sources VERITAS observations 17tween and (from radio VERITAS terres- observing bursts were runs detected whenremaining 15 by the bursts GBT, telescopes have 2 contemporaneous were optical ofare and not which presented gamma-ray acquiring occurred here. exposures with gamma-ray be- Exact VERITAS, burst data. and times will The be reported in a futurewere publication. conducted between 29 December 2018and and were 12 timed February to 2019. provide TheExperiment exposures coincident (CHIME) total [ observing 8.2 with hours the Canadian Hydrogen Intensity Mapping PoS(ICRC2019)698 1 − s cuts ]. It 2 − ]. The 12 gamma- soft 18 Jamie Holder soft ] and [ 18 photons cm 13 " indicates the location − × ms window centered on 10 − × above 200 GeV for 26 1 . − cuts. s 2 − cuts and 6 differential power law spectrum. The rel- moderate 2 − soft E photons cm 13 3 − shows the significance skymap for observations of 10 1 × events, where the background is estimated using the stan- cuts. 25 5 . − above 300 GeV for 10 ]. At the location of FRB 121102, no gamma-ray like events 1 − × ). Figure above 300 GeV for s 21 ◦ 2 1 cuts, for an assumed moderate − − 46 s 2 ∼ − method [ moderate photons cm 12 − photons cm 10 13 − Significance skymap of the region around FRB 180814.J0422+73. The " × 10 86 . ring-background × The methodology for a comprehensive burst search has been discussed in [ Upper limits for the archival observations of FRB 121102 have been reported in [ ]. These cuts correspond to the lowest energy threshold and to more strict background re- 24 . 19 of the repeater, while thespread black function. circle No in evidence the for lower steady left gamma-ray emission shows is the seen. approximate size of the gamma-ray point ray selection cuts, the meanthe reported number radio of burst background time is eventsdard 9 within a 10 passed the cuts forwith any expectation of in the the 15 absence bursts of with a contemporaneous signal observations. (the This probability is of consistent observing zero events is 0.99991 Figure 1: FRB 180814.J0422+73 using 95% confidence limits for steadyduring emission which 15 during FRBs the occurred, observationsand are of 1 5 25 November 2017 alone, typically includes searching multiple time windows, withas multiple searching levels for of delayed event or selection, as precursorpublication. well emission. Here This complete we analysis present will thegamma-ray be simplest and reported analysis radio in a only emission future — from a FRB 121102. search for After strictly the contemporaneous application of standard VERITAS Observations of FRBs [ jection, respectively. The 95% confidence integral9 flux upper limits for FRB 180814.J0422+73above are 500 GeV for atively high energy thresholds areobservations a were result made of ( the moderately low elevation angle at which these PoS(ICRC2019)698 Jamie Holder 15 s) exposures > ]. 24 10 is consistent with , ]. The VERITAS limits > 23 20 are the expected magnitudes for optical 2 4 ]. While fewer than 100 bursts detections have been 22 above 200 GeV. The combined upper limit over all 15 bursts is 1 . This allows contemporaneous radio and IACT searches for non- ], since the background rate is negligible, the 95% confidence upper − ◦ . s 7 1 . 12 2 − s − 2 − 1% of the radio energy flux for an assumed 0.4 Jy radio burst with a 10 ms optical photons cm overhead strip of the sky. VERITAS and CHIME both view the northern sky and are 7 ∼ 2 photons cm − 8 10 − × 10 6 During the observations of 25 November 2017, the VERITAS optical photometry hardware A preliminary search for optical signals of <0.1 s at signal/noise of The search for fast radio burst counterparts using imaging atmospheric Cherenkov telescopes The commissioning of CHIME provides an even more promising avenue to explore, and one 200deg . × 7 ≥ . published so far, the extrapolatedtherefore, event already rate contain across many the observationsproximately sky of is one FRBs, thousands unobserved for per by every day. anythe few radio true IACT days telescope rate archives, — of of ap- observations, FRBs.lisecond depending timescales A is on search therefore of the worthwhile. these IACT Previousnotably extensive "blind" field those archives burst motivated for of searches by gamma-ray have view predicted been event emission and have performed, clusters typically from on used evaporating mil- primordial a lower black limit holes, of but seconds, these as opposed to milliseconds [ was only partially commissioned.scope The 1), system and was 12 installed photomultiplier tubes onwas channels only observing were one connected, the of including location the theaccurately of central telescopes timestamped pixel FRB (Tele- which — 121102. although accurate The timingphotometry sampling may to rate be bright recoverable transient was by optical 300 comparing eventspath, Hz. (meteors) the which recorded optical includes in The GPS the data timing. gamma-ray data were acquisition not is still in its earliest stages.continue, Coordinated but observing the campaigns prospects on to the observeprobe repeating non-repeating an burst bursts locations entirely are will different also class extremely of promising object and [ may for which VERITAS is uniquely suited.a CHIME is now operating and is continuously monitoring 4.2 Optical search only background events (likely meteors). Plotted incounterpart figure bursts of duration from 0.1 to 10 ms following the scheme of [ compared to the shortjudging burst the optical duration, counterpart fluence demonstrating for that FRBs. VERITAS is an5. excellent facility Discussion for repeating FRBs with a high probability of successfully performing a coincident observation. In separated in longitude by 8 3 burst duration, up toplotted a is matching a radio comparison of fluxoptical the transient for VERITAS facilities: optical an the photometry Large optical Synoptic sensitivity Sky counterpart(ZFT), compared Telescope (LSST), and to of the the Zwicky a 0.1 Transient EVRYSCOPE. ms number Factory The of duration.by VERITAS limits the are Also LSST within and a superior factor to of 10 many of other those transient achievable facilities due to their long ( VERITAS Observations of FRBs for each burst). Following [ limit to the number of eventsof per 5 burst is 3.56 events, corresponding to an integral flux upper limit range from PoS(ICRC2019)698 3 0 Jamie Holder 1 2 0 1 100 m leads to a noticeable par- ∼ ) for meteors at a typical altitude of ◦ EVRYSCOPE 07 . 1 0 ZTF R 1 F / o F 5 VERITAS ECM 0 0 1 ] for an FRB of 0.4 Jy and optical burst durations of 0.1 (blue), 1 (green), 20 1 0 1 0.1ms 1ms 5ms 10ms LSST 2 The equivalent magnitude for an optical counterpart to an FRB as a function of the radio lumi- 0

0 5 1

10 20 15 30 25 Optical photometry of FRBs with IACTs also has a promising future. All four VERITAS Equivalent Magnitude Equivalent 80 km. Astrophysical optical transients will not be subject to this effect, and so comparing the Figure 2: nosity, following the scheme of [ order to overlap VERITAS observationstrack with a the position CHIME on field the ofularly celestial view, met sphere it during 35 is standard minutes gamma-ray simply afterobserving observations necessary culmination, and program. to can a Coincident easily requirement CHIME/VERITAS be observations which2019 factored have is into been and reg- the performed will VERITAS throughout be examinedpublic. for overlapping burst observations once the CHIME results are made telescopes are now equippedmultiplier with tube the channels necessary sampled electronics atwell-suited and 2400 for typically Hz. such operate searches, The since with four-telescope the 2 VERITAS telescope array photo- separation is of particularly 5 (yellow) and 10 msTAS (burgundy) ECM), respectively. 15 s Solid (LSST), lines 30 arelimiting s for magnitudes (Zwicky for an Transient the observation Factory) respective exposure and instruments. of 120 s 1 (EVRYSCOPE). ms The (VERI- red lines are the allax of half of the∼ photomultiplier tube pixel diameter (0 optical intensity and pulse profile between multiplelocal telescopes background should allow to the be otherwise suppressed. dominant VERITAS Observations of FRBs PoS(ICRC2019)698 Jamie Holder , arXiv e-prints, , 34th , Nature, 566, 235, , Science, 318, 777, , Ann. Rev. A & A, in , Astronomy and Astrophysics , Nature, 531, 202, 2016. arXiv:1603.00581 , The Astrophysical Journal, 875, L19, 2019. Second Repeating FRB 180814.J0422+73: , A&A, 597, A115, 2017. arXiv:1611.09209 Fast radio bursts 6 , Astropart. Phys., 25, 391, 2006. Performance of the VERITAS experiment A second source of repeating fast radio bursts Fast Radio Bursts: An Extragalactic Enigma A repeating fast radio burst First limits on the very-high energy gamma-ray afterglow emission of a fast A Search for Brief Optical Flashes Associated with the SETI Target KIC Constraining very-high-energy and optical emission from FRB 121102 with A Search for High-Energy Counterparts to Fast Radio Bursts , MNRAS, 481, 2479, 2018. arXiv:1809.00663 A Bright Millisecond Radio Burst of Extragalactic Origin Direct measurement of stellar angular diameters by the VERITAS Cherenkov An extreme magneto-ionic environment associated with the fast radio burst source The first VERITAS telescope , Nature, 553, 182, 2018. arXiv:1801.03965 , Nature Astronomy, 249, 2019. , ApJ, 818, L33, 2016. arXiv:1602.00987 radio burst. H.E.S.S. observations of FRB 150418 FRB 121102 telescopes 2019. arXiv:1901.04525 arXiv:1905.06818, 2019. Ten-year Fermi-LAT Upper Limits and Implications arXiv:1903.07329 8462852 International Cosmic Ray Conference (ICRC2015), 34, 771, 2015. arXiv:1508.07070 the MAGIC telescopes arXiv:astro-ph/0604119 press, 2019. arXiv:1906.05878 2007. arXiv:0709.4301 Review, 27, 4, 2019. arXiv:1904.07947 This research is supported by grants from the U.S. Department of Energy Office of Science, the [6] Michilli, D., et al., [7] Cunningham, V., et al., [8] Yang, Yu-Han, Zhang, Bin-Bin, and Zhang, Bing, [9] Abeysekara, A. U., et al., [1] Lorimer, D. R., et al., [2] Petroff, E., Hessels, J. W. T., and Lorimer, D. R., [3] J. M. Cordes and S. Chatterjee, [4] Spitler, L. G., Scholz, P., et al, [5] CHIME/FRB Collaboration, et al., [11] H. E. S. S. Collaboration, [10] Benbow, W., et al., [12] MAGIC Collaboration, [13] Holder, J., et al., [14] Park, N. and the VERITAS Collaboration, U.S. National Science Foundation and the Smithsonianresearch Institution, used and by resources NSERC provided in Canada. byScience This the Foundation Open and Science the U.S. Grid,National Department which Energy of is Research Energy’s supported Office Scientific by of ComputingOffice the Science, of Center National and Science (NERSC), User resources a Facility of operated U.S. the edge under Department the Contract of No. excellent Energy work DE-AC02-05CH11231. We of acknowl- and the at technical the support collaborating staff institutions at in the the construction Fred and Lawrence operation Whipple of Observatory theReferences instrument. VERITAS Observations of FRBs 6. Acknowledgements PoS(ICRC2019)698 , Jamie Holder . 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