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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"

8473 results found.

  1. GRB 260730B: AstroSat CZTI detection
  2. EP260727a: SAO RAS optical observations
  3. GRB 260727A: AbAO and SAO RAS optical observations
  4. EP260727a: 1.5m OSN optical counterpart detection
  5. EP260727a: OHP/T193 optical observations
  6. GRB 260726A: Liverpool Telescope optical observations
  7. GRB 260726A: J-band upper limit with WINTER
  8. GRB 260726A: SVOM/VT optical candidate
  9. GRB 260727A: AstroSat CZTI detection
  10. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  11. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  12. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 260618B: EP-FXT follow-up observation upper limit
  14. GRB 260714B: COLIBRÍ optical counterpart candidate
  15. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  16. GRB 260710A: AstroSat CZTI detection
  17. GRB 260709A: AstroSat CZTI detection
  18. GRB 260714B: AstroSat CZTI detection
  19. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  20. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  21. GRB 260705A: ATCA radio observations
  22. GRB 260619A: SVOM/VT continuous optical observations
  23. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  24. GRB 260708A: GRANDMA Optical Observations
  25. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  26. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  27. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  28. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  29. GRB 260705C: AstroSat CZTI detection
  30. GRB 260708A: Kilonova-Catcher optical afterglow detection
  31. IceCube-260708A: One candidate from the Zwicky Transient Facility
  32. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  33. EP260707a is not a real source
  34. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  35. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  36. IceCube-260704A: No candidates from the Zwicky Transient Facility
  37. The EP-WXT trigger 01709274151 is likely a flaring star
  38. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  39. Fermi GBM Sub-Threshold Detection of GRB 260705A
  40. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  41. GRB 260629A: AstroSat CZTI detection
  42. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  43. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  44. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 260619A: SVOM/VT optical counterpart confirmation
  46. GRB 260618B: SVOM/VT optical candidate
  47. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  48. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  49. GRB 260616B: AstroSat CZTI detection
  50. GRB 260616A: AstroSat CZTI detection
  51. EP260618a: COLIBRÍ optical counterpart candidate
  52. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 260614A: AstroSat CZTI detection
  54. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  55. GRB 260614B: SVOM/VT optical candidate from VHF data
  56. GRB 260603C: AstroSat CZTI detection
  57. GRB 260610B / AT2026owq: GRANDMA optical observations
  58. IceCube-260610A: No candidates from the Zwicky Transient Facility
  59. IceCube-260610A: EP-FXT follow-up observation
  60. GRB 260610B: DDOTI optical observations
  61. GRB 260610B: GOTO optical counterpart candidate
  62. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  63. EP260610b: Gemini North optical counterpart candidate
  64. GRB 260604C: AstroSat CZTI detection
  65. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  66. GRB 260607B: AstroSat CZTI detection
  67. GRB 260607A: TRT optical observations
  68. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  69. GRB 260601B / EP260601a: AstroSat CZTI detection
  70. GRB 260604C: Correction to GCN 44828
  71. GRB 260604C: LAST detection of optical counterpart candidate
  72. EP260602a: NOT NIR J-band observations
  73. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  74. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  75. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  76. EP260602a: SVOM/VT optical candidate
  77. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  78. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  79. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  80. The EP-WXT trigger 01709266272 is likely a flaring star
  81. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  82. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  83. GRB 260529A: GOTO tentative optical afterglow candidate
  84. GRB 260527A/EP260527a: FTW optical and NIR observations
  85. The EP-WXT trigger 01709266147 is likely a flaring star
  86. GRB 260525A: AstroSat CZTI detection
  87. GRB 260523B: AstroSat CZTI detection
  88. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  89. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  90. GRB 260518A: AstroSat CZTI detection of a long burst
  91. GRB 260516D: SVOM/ECLAIRs refined analysis
  92. GRB 260515A: SVOM/ECLAIRs refined analysis
  93. GRB 260421B: radio detection with the VLA
  94. GRB 260516D: GOTO optical counterpart detection
  95. GRB 260516D: SVOM/VT optical bright candidate
  96. EP260514a: NOT optical counterpart confirmation
  97. EP260514a: TRT optical counterpart candidate
  98. EP260514a: SVOM/VT optical candidate
  99. GRB 260515A: SVOM/VT optical candidate from VHF data
  100. GRB 260515A: JinShan optical counterpart candidate

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