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dc.rights.licenseCopyright © 2021, The Author(s)-
dc.contributor.authorVillarroel, B.-
dc.contributor.authorMarcy, G. W.-
dc.contributor.authorGeier, S.-
dc.contributor.authorStreblyanska, A.-
dc.contributor.authorSolano, E.-
dc.contributor.authorAndruk, V. N.-
dc.contributor.authorShultz, M. E.-
dc.contributor.authorGupta, A. C.-
dc.contributor.authorMattsson, L.-
dc.identifier.citationScientific Reports 11: 12794(2021)es
dc.description.abstractNine point sources appeared within half an hour on a region within ∼ 10 arcmin of a red-sensitive photographic plate taken in April 1950 as part of the historic Palomar Sky Survey. All nine sources are absent on both previous and later photographic images, and absent in modern surveys with CCD detectors which go several magnitudes deeper. We present deep CCD images with the 10.4-m Gran Telescopio Canarias, reaching brightness r∼26 mag, that reveal possible optical counterparts, although these counterparts could equally well be just chance projections. The incidence of transients in the investigated photographic plate is far higher than expected from known detection rates of optical counterparts to e.g. flaring dwarf stars, Fast Radio Bursts, Gamma Ray Bursts or microlensing events. One possible explanation is that the plates have been subjected to an unknown type of contamination producing mainly point sources with of varying intensities along with some mechanism of concentration within a radius of ∼ 10 arcmin on the plate. If contamination as an explanation can be fully excluded, another possibility is fast (t <0.5 s) solar reflections from objects near geosynchronous orbits. An alternative route to confirm the latter scenario is by looking for images from the First Palomar Sky Survey where multiple transients follow a
dc.description.sponsorshipBased on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. The authors wish to thank the two anonymous referees that had excellent and constructive suggestions that significantly improved the paper, among them the possibility of a human source of contamination and meteorites. The authors wish to thank Martín López Corredoira for help with the statistical considerations and Brian McLean for help with retrieving the complete POSS plates in Supp. Info. Table 1. B.V. thanks Martin Ward, Guy Nir, Beatrice Eriksson and Ignacio Trujillo for helpful discussions. This research has made use of the Spanish Virtual Observatory ( supported from the Spanish MINECO/FEDER through grant AyA2017-84089. B.V. is funded by the Swedish Research Council (Vetenskapsrådet, grant no. 2017-06372) and is also supported by the The L’Oréal - UNESCO For Women in Science Sweden Prize with support of the Young Academy of Sweden. She is also supported by Märta och Erik Holmbergs donation. M.E.S. acknowledges financial support from the Annie Jump Cannon Fellowship, supported by the University of Delaware and endowed by the Mount Cuba Astronomical
dc.publisherNature Research Journalses
dc.relationinfo:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/AYA2017-84089-P/ES/EL OBSERVATORIO VIRTUAL ESPAÑOL. EXPLOTACION CIENTIFICO-TECNICA DE ARCHIVOS ASTRONOMICOS/-
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 Internationales
dc.subjectAstronomical instrumentationes
dc.subjectParticle astrophysicses
dc.subjectTime domain astronomyes
dc.subjectTransient astrophysical phenomenaes
dc.titleExploring nine simultaneously occurring transients on April 12th 1950es
dc.contributor.funderAgencia Estatal de Investigación (AEI)-
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