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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

20347 results found.

  1. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  2. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  3. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  4. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  5. GRB 260809A: NOT optical observations
  6. GRB260809A: MAO/AZT-22 optical observations
  7. GRB260809A: OHP/T193 optical observations
  8. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  9. EP260809a: J-band upper limit with WINTER
  10. GRB 260808B: J-band upper limit with WINTER
  11. GRB 260808B: SVOM/ECLAIRs refined analysis
  12. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  13. GRB 260809A: SVOM detection of a faint burst
  14. GRB 260808B: Liverpool Telescope optical observations
  15. GRB 260808B: NOT optical observations
  16. GRB 260808B: LCO optical observations
  17. EP260809a: COLIBRÍ optical observations
  18. EP260809a: LCO optical observation
  19. EP260809a: OHP/T193 optical observations
  20. GRB260808B: OHP/T193 optical observations
  21. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  22. EP260809a: Einstein Probe detection of an X-ray transient
  23. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  24. GRB 260808B: SVOM/VT optical candidate from VHF data
  25. GRB 260808B: SVOM detection of a faint burst
  26. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  27. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  28. EP260806a: COLIBRÍ optical observations
  29. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. EP260806a: SVOM/VT optical observation
  31. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  32. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260806a: LCO likely optical counterpart
  34. EP260806a: Einstein Probe detection of an X-ray transient
  35. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  36. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  37. GRB 260804A: Fermi GBM Final Real-time Localization
  38. GRB 260802A: SVOM/VT optical upper limits from VHF data
  39. GRB 260802A: LCO optical upper limits
  40. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  41. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  42. GRB 260731A: AstroSat CZTI detection of a long burst
  43. EP260731a: COLIBRÍ optical upper limit
  44. EP260731a: NOT optical upper limit
  45. EP260731a: Einstein Probe detection of an X-ray transient
  46. GRB 260727A: SVOM/ECLAIRs refined analysis
  47. GRB 260726A: SVOM/ECLAIRs refined analysis
  48. EP260728a: COLIBRÍ optical upper limit
  49. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  50. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  51. EP260729a: Einstein Probe detection of an X-ray transient
  52. EP260727a: SAO RAS optical observations
  53. GRB 260727A: AbAO and SAO RAS optical observations
  54. EP260728a: EP-FXT follow-up observation
  55. EP260728a: Einstein Probe detection of a fast X-ray transient
  56. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  57. EP260727a: OHP/T193 optical observations
  58. GRB 260726A: Liverpool Telescope optical observations
  59. GRB 260727A: Liverpool Telescope optical upper limits
  60. EP260727a: Liverpool Telescope confirmation of optical counterpart
  61. EP260727a: Einstein Probe detection of an X-ray transient
  62. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  63. GRB 260726A: J-band upper limit with WINTER
  64. GRB 260727A: J-band upper limit with WINTER
  65. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  66. EP260723a: SVOM/ECLAIRs Upper Limit
  67. GRB 260727A: AstroSat CZTI detection
  68. GRB 260727A: Kilonova-Catcher optical upper limit
  69. GRB 260727A: LCO optical upper limits
  70. GRB 260726A: SVOM detection of a burst
  71. EP260725a: EP-WXT detection of an X-ray transient
  72. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  73. GRB 260601A: cubesat Avion detection
  74. GRB 260718A: SVOM/ECLAIRs refined analysis
  75. EP260723a: SVOM/VT optical observation
  76. EP260723a: COLIBRÍ optical observations
  77. EP260723a: NOT optical conterpart confirmation
  78. EP260723a: Liverpool Telescope likely optical counterpart
  79. EP260723a: EP-WXT detection of a fast X-ray transient
  80. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  81. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  82. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  83. GRB 260705A: Retraction of optical counterpart
  84. GRB 260718A: LCO optical upper limits
  85. GRB 260710A: SVOM/GRM observation
  86. GRB 260718A : GRANDMA and KNC upper limits
  87. GRB 260718A: SVOM/VT optical upper limits
  88. GRB 260718A: SVOM/VT optical upper limits from VHF data
  89. GRB 260714B: SVOM/GRM observation
  90. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  91. GRB 260714B: GECAM-B observation of a burst
  92. GRB 260714B: COLIBRÍ optical counterpart candidate
  93. sb26071506: SVOM detection of a X-ray transient
  94. EP260703a: SVOM/ECLAIRs Upper Limit
  95. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  96. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  97. GRB 260706A: ATCA detection of possible radio counterpart
  98. GRB 260705A: ATCA radio observations
  99. EP260713a: Einstein Probe detection of an X-ray transient
  100. EP260623a: KAIT optical observations

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