J/A+A/691/A181ivo://CDS.VizieR/J/A+A/691/A181doi:10.26093/cds/vizier.36910181CDSPessi P.J.Durgesh R.Nakazono L.Hayes E.E.Oliveira R.A.P.,Ishida E.E.O.Moitinho A.Krone-Martins A.Moews B.de Souza R.S.,Beck R.Kuhn M.A.Nowak K.Vaughan S. (for the COIN collaboration)2025-02-18T20:01:53Z2024-11-12T07:59:04ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frtransient-sourcesphotometryclassificationTransient astronomical events that exhibit no discernible association with a host galaxy are commonly referred to as hostless. These rare phenomena can offer unique insights into the properties and evolution of stars and galaxies. However, the sheer number of transients captured by contemporary high-cadence astronomical surveys renders the manual identification of all potential hostless transients impractical. Therefore, creating a systematic identification tool is crucial for studying these elusive events. We present the ExtragaLactic alErt Pipeline for Hostless AstroNomical Transients (ELEPHANT), a framework for filtering hostless transients in astronomical data streams. It was designed to process alerts from the Zwicky Transient Facility (ZTF) presented in the Fink broker; however, its underlying concept can be applied to other data sources. We used Fink to access all the ZTF alerts produced between January 2022 and December 2023, selecting alerts associated with extragalactic transients reported in SIMBAD or TNS, as well as those classified as supernovae (SNe) or kilonovae (KNe) by the machine learning (ML) classifiers within the broker. We then processed the associated stamps using a sequence of image analysis techniques to retrieve hostless candidates. We find that less than 2% of all analyzed transients are potentially hostless. Among them, only around 10 percent have a spectroscopic class reported on TNS, with type Ia SNe being the most common class, followed by superluminous SNe. In particular, among the hostless candidates retrieved by our pipeline, there is SN 2018ibb, which has been proposed to be a pair instability SN candidate, and SN 2022ann, one of only five known SNe Icn. When no class is reported on TNS, the dominant classes are quasi-stellar object (QSO) and SN candidates, with the former obtained from SIMBAD and the latter inferred using the Fink ML classifier. ELEPHANT represents an effective strategy to filter extragalactic events within large and complex astronomical alert streams. There are many applications for which this pipeline will be useful, ranging from transient selection for follow-up to studies of transient environments. The results presented here demonstrate the feasibility of developing specially crafted pipelines that enable a variety of scientific studies based on large-scale surveys.2024A&A...691A.181Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/691/A181CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/691/A181https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/691/A181http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/691/A181https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/691/A181https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/691/A181http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/691/A181GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/691/A181/table2 (Hostless candidates with spectral class in TNS)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/691/A181/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/691/A181/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/691/A181/table2?GETtext/xml+votable180.050000true320.6049167-11.94856110.005555555555555556Cone search capability for table J/A+A/691/A181/tabled1 (Hostless candidates without spectral class in TNS)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/691/A181/tabled1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/691/A181/tabled1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/691/A181/tabled1?GETtext/xml+votable180.050000true46.6946.15359170.0055555555555555566/107 134 154 178 219 243 247 250 392 526 580 640 661 675 684 744 749 751 787 839 929 974 995 1154 1210 1262 1374 1479 1490 1493 1526 1564 1639 1885 1902 1917 1994 2047 2056 2061 2064-2065 2072 2082 2092 2108 2113-2114 2121 2135 2168 2182 2191 2198 2213 2229 2237 2240 2243 2245 2264 2286 2336 2340 2356 2398 2545 2554 2564 2576 2593 2622 2629-2630 2646 2666 2668 2704-2705 2709 2712 2745 2758 2821 2889 2900 2930 2958 2985 3024 3079 3125 3136 3161 3198 3240 3444 3561 3569 3599 3801 3819 3887 3928 3993 4022 4067 4135 4137 4153 4169 4200 4232 4256 4270 4272 4295 4307 4375 4412 4463 4482 4503 4561 4565 4573 4587 4590 4608 4611 4616 4623 4628 4651 4660 4666 4691 4711 4742 4763 4781 4785-4786 4794 4796 4811-4812 4817 4829-4830 4832 4851 4854 4859 4864 4874 4904 4907-4908 4915 4929 4942 4950 4967 4976 4986 5005 5013 5044 5046 5052 5055 5058 5066 5075 5081 5095 5105-5106 5109 5126-5127 5131 5146 5149 5154 5191 5222 5224 5241 5255 5261 5265-5266 5270 5281 5296 5305 5325 5328-5329 5334 5337 5340 5347 5358 5361 5378 5386 5392 5398 5403 5413 5424 5443 5458 5469 5472 5498-5499 5512 5515 5521 5523-5524 5536 5540-5541 5545-5547 5553 5556 5565 5582 5584 5587 5590 5595 5601 5604 5612-5614 5623 5641 5645 5654 5676-5677 5688 5704 5712 5724 5747 5754 5756 5772 5777 5779 5790 5796 5801 5805 5808 5812-5813 5817 5821 5832 5837 5885 5891 5896 5911 5913 5920 5925 5942 5947 5969 5982-5983 5998 6007 6046 6058 6062 6105 6113 6115-6116 6127 6143 6170 6182 6193-6194 6205 6222 6226 6229 6231 6240 6243 6249 6254 6256 6263 6271-6272 6300 6365 6379 6393 6410 6418 6420-6421 6437 6445 6458 6463 6475 6496 6530 6533-6534 6536 6540 6550 6553 6556 6559 6574 6580 6584 6597 6599 6611 6617 6623 6625 6627 6634 6637 6648 6652 6654 6659-6660 6695 6730 6737 6753 6758 6776 6863 6868 6875 6933 6947 6988 7088 7170 7173 7178-7181 7183 7185 7190 7193 7199-7200 7205 7212 7215 7218 7222 7238-7239 7245 7252 7261-7262 7286 7293 7298-7299 7303 7305 7310-7312 7321 7325 7331 7339 7342 7344 7350 7361 7364 7371-7372 7375 7382 7387-7388 7394 7404 7425 7435 7441 7443 7448 7465 7468 7479 7498 7504 7518 7546 7552 7567 7577 7617 7644 7649 7678 7681 7710 7835 7837 7854 7862 7864 7877 7883 7888 7938 7965 8043 8057 8103 8109 8140 8219 8226 8228 8233 8237 8257 8271 8295 8298-8299 8331 8340 8346 8365 8375-8376 8385 8420 8431 8433 8438 8445 8464 8504 8512 8519 8573 8588 8621 8634 8646 8655 8662 8679 8683 8701 8717 8728 8737 8756 8775 8794 8805 8807 8842 8856 8879 8982 8988 8999 9015 9026 9034 9037 9048 9054 9061 9099 9105 9150 9176 9186 9198 9200 9205-9206 9214-9215 9217 9230 9239 9242 9251 9270 9284 9318 9321 9323 9330 9335 9342 9360 9367 9373 9382 9392 9399 9407 9416 9418 9439 9457 9468 9475 9508 9517 9525 9530 9535 9552 9558 9562 9603 9606 9620 9622 9641 9670 9707 9711 9716 9719 9726 9733 9735 9737 9745 9766 9769 9771 9774 9791 9824 9831 9843 9862 9869 9872 9874 9882 9891 9898 9908 9912 9931 9934 9947 9955 9966 9977 9985 9989 10003 10006 10025 10039 10041 10063 10112 10116 10161 10168-10169 10173 10190 10203 10220 10232 10236 10241 10312 10331 10339 10352 10368 10384 10397 10443 10465 10467 10470 10514 10531 10548 10554 10564 10566 10571 10576 10585 10588 10590-10591 10598 10618 10621 10632 10638 10643 10647 10656 10661 10681 10683 10690-10691 10694 10697-10698 10716 10720 10724 10727 10735-10736 10738 10741 10754 10770 10797 10813 10819 10836 10839 10849 10853 10868 10884 10898 10913 10926 10932 10953 10959 10983 10994-10995 11003 11021 11032 11036 11039 11050 11052 11054 11058 11060 11072 11078 11086 11090 11100 11102 11122 11129 11132-11133 11148 11152 11165 11169 11186 11190 11213 11231 11233 11251 11254 11266 11272-11274 11281 11289 11291 11296-11297 11328-11330 11337 11339 11347-11348 11350 11358 11365 11377 11382 11387 11410 11413 11416 11429 11438 11442 11451 11466 11476 11478 11492 11496 11506 11519 11587 11591 11629 11632 11669 11697 11699 11724 11762 11779 11800 11807 11830 11832 11841 11869 11914 11946 11948 11950 11976 11995 12002 12033 12045 12092 12100 12122 12136 12152 12176 12181 12245 12292 12352 12395 12400 12408 12462 12473 12489 12545 12568 12600 12618 12621 12635 12652 12751 12765 12820 12877 13264 13267 13282 13308 13317 13325 13328 13344 13357 13362 13365 13368 13370 13373 13375 13384 13391 13400 13435 13445 13448 13451 13462 13469 13480 13506 13508 13513 13569 13575 13584 13595 13644 13661 13679 13690 13748 13766 13820 13876 13915 13919 13953 14094 14124 14150 14283 14526 14558 14570 14581-14582 14766 14911 14964 14970 14998 15013 15030 15045 15062 15064 15073 15107 15119 15156 15172 15274 15304 15314 15339 15342 15609 15616 15862 15864 15868 15970 16022 16038 16112 16115 16118 16131 16211 16281 16323 16510 16571 16618 16667 16680 16702 16717 16734 16777 16809 16813 16934 16964 16991 17026 17203 17206 17257 17263 17265 17300 17325-17326 17366 17455 17525 17552 17597 17604 17606 17618 17627 17636-17637 17645 17652 17661-17662 17695 17698 17718 17725 17737 17767 17779 17782 17795 17800 17809-17810 17813 17820-17822 17852 17854 17866 17887 17900 17920 17922 17961 17968-17969 17977 17985 17987 17990 18005 18016 18032 18038 18045-18046 18064 18081 18094-18095 18106 18112 18118-18119 18123 18127 18140 18161 18163 18181 18184 18203 18210 18215 18218 18221 18226 18248 18257 18272 18289 18296 18321 18335 18380 18397 18403 18430-18431 18614 18640 18643-18644 18666 18717 18753 18758 18769 18783 18797-18798 18806 18808-18810 18823 18825 18838 18845 18854 18880 18882-18883 18885 18888 18915 18944 18973 18998 19026 19034 19046 19066 19068 19080 19100 19220 19231 19239 19254 19263 19271 19275 19325 19333 19347 19357 19385 19390 19395 19406 19420 19427 19444 19447 19449 19493 19506 19562 19640-19641 19646 19656 19680 19699 19709 19725 19753 19770 19793 19798 19810 19825 19834 19884-19885 19907 19909 19913 19932 19942 19958 20005 20015 20033 20047 20064 20069 20091 20093 20117-20118 20122 20127 20136 20182 20196 20223 20228 20231 20244 20246 20264 20273 20298 20300 20302 20309 20312 20329 20346 20350 20360 20373 20375 20384 20395 20405 20408 20423 20430 20442-20443 20464 20659 20735 20858 21002 21047 21089 21154 21355 21379 21413 21415 21553 21713 21866 21971 21974 21977 21991 22122 22241 22328 22373 22398 22530 22563 22719 22955 23097 23101 23104 23189 23210 23324 23669 23753 23773 23853 24020 24103 24235 24525 24766 24811 24914 25010 25036 25117 25244 25333 25421 25474 25484 25522 25582 25591 25663 25721 25812 25819 25828-25829 25834 25837 25849 25852 25869 25948 26005 26023 26032 26045 26070 26120 26125 26197 26203 26249 26267 26291 26304 26368 26394 26428 26439 26527 26530 26542 26558 26562 26596-26597 26605 26611 26616 26770 26826 26836 26885 26950 26993 27010 27030 27110 27154 27160 27186 27205 27211 27214 27218 27226 27228 27244 27262 27278 27308 27336 27348 27355 27367 27392 27425 27443 27446 27462 27584 27609 27647 27654 27670 27675 27718 27733 27746 27768 27796 27837 27889 27941 27998 28026 28069 28107 28127 28199 28215 28226 28278 28294 28320 28326 28328 28332 28385 28388 28405 28483 28513 28517 28520 28526 28540 28543 28551 28553 28572-28573 28580 28594 28612 28622 28628 28631-28632 28637-28638 28643 28664 28872 28918 29046 29350 29461 29668 29828 29887 29948 29973 29987 30004 30027 30043 30065 30317 30476 30716 30723 30874 30906 31092 31116 31230 31327 31339 31357 31396 31398-31399 31410 31430 31445 31449 31468 31474 31486 31494 31531 31533 31571 31591 31597 31647 31651 31667 31669 31690 31704 31708 31715 31743 31840 31857 31917 31923 32094 32145 32166 32206 32242 32278 32301 32322 32327 32336 32342 32347 32350 32356 32380 32416 32474 32495 32548 32555 32563 32571 32625 32629 32708 32753 34761 34788 34795 35804 35828 36035 36069 36240 36253-36254 36276 36357 36460 36466 36472 36476 36487 36509 36587 36590-36592 36683 36690 36702 36719 36726 36741 36750 36753 36765 36790 36798 38891 40283 40301 40360 40405 40503 40527 40535 40549 40565 40869 40908 40946 43960 44005 44120 44122-44123 44135 44140-44141 44144-44146 44152 44224 44229 44232 44263 44373 44440 44586 44607 44669 44783 44798 44966 45001 45030 48062 48378 48431 48450 48466 48473 48480 48485 48495 48524 48561 48651 48673 48703 48718 48844 48894 48911 48931 48935 48972 49001 49041 49096 49101 49110 49114https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/691/A181?format=asciidefaultJ/A+A/691/A181/table2Hostless candidates with spectral class in TNSrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIAUnameOfficial IAU namemeta.idcharZTFnameZTF internal namemeta.id;meta.maincharRAJ2000Right Ascencion (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainClassSpectroscopic classificationmeta.code.classcharConfirmed[xv] Confirmation of lack of obvious host (1)meta.codecharCommentsCommentsmeta.notecharJ/A+A/691/A181/tabled1Hostless candidates without spectral class in TNSIAUnameOfficial IAU namemeta.idcharZTFnameZTF internal namemeta.id;meta.maincharRAJ2000Right Ascencion (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainClassMachine learning assigned classificationmeta.code.classcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint