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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"

21792 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  2. GRB 260708A: LCO optical observations
  3. EP260711a: Einstein Probe detection of an X-ray transient
  4. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  5. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  6. GRB 260704A: SVOM/ECLAIRs refined analysis
  7. GRB 260706A : GRANDMA Upper limits
  8. GRB 260708A: Kilonova-Catcher optical afterglow detection
  9. IceCube-260708A: One candidate from the Zwicky Transient Facility
  10. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  11. IceCube Alert 260709A: Global MASTER-Net observations report
  12. LAT GRB260708.42: Global MASTER-Net observations report
  13. GRB 260706A: SVOM/VT optical upper limits
  14. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  15. GRB 260706A: SVOM/ECLAIRs refined analysis
  16. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  17. GRB 260706A: REM optical/NIR observations
  18. IceCube-260704A: No candidates from the Zwicky Transient Facility
  19. GRB 260705A: SVOM/ECLAIRs refined analysis
  20. IceCube260704A: OHP/T193 optical observations
  21. GRB 260704A: NOT optical upper limits
  22. Fermi GBM Sub-Threshold Detection of GRB 260705A
  23. EP260703a: EP-WXT detection of a fast X-ray transient
  24. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  25. Fermi trigger No 804738310: Global MASTER-Net observations report
  26. Fermi GRB 260703A: Global MASTER-Net observations report
  27. GRB 260610B: VLA detection
  28. GRB 260614B: ATCA Radio Upper Limits
  29. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  30. Fermi trigger No 804552016: Global MASTER-Net observations report
  31. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  32. Fermi GRB 260628A: Global MASTER-Net observations report
  33. EP260628a: EP-WXT detection of a fast X-ray transient
  34. EP260626a: EP-WXT detection of a fast X-ray transient
  35. EP260623a: FTW optical and NIR observations
  36. GRB 260619A: SVOM/ECLAIRs refined analysis
  37. EP260623a: Liverpool Telescope optical observations
  38. EP260623a: WINTER J-band observations
  39. EP260623a: Optical follow-up observations with Kinder
  40. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  41. EP260623a: SVOM/VT optical observations
  42. EP260623a: TRT optical observations
  43. EP260623a: REM optical/NIR afterglow detection
  44. EP 260623a: COLIBRÍ optical observations
  45. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  46. EP260618a: Liverpool Telescope optical observations
  47. GRB 260619A: NOT optical observations
  48. GRB 260618B: LCO optical observations
  49. EP260618a: JinShan optical observations
  50. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  51. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  52. GRB 260619A: SVOM/VT optical counterpart confirmation
  53. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  54. GRB 260618B: SVOM/VT optical candidate
  55. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  56. EP260618a: OHP/T193 optical observations
  57. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  58. GRB 260619A: Kilonova-Catcher optical upper limit
  59. EP260618a: EP-FXT follow-up observation
  60. EP260618a: COLIBRÍ optical counterpart candidate
  61. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  62. EP260618a: EP-WXT detection of an X-ray transient
  63. GRB 260610B: AbAO optical observations
  64. EP260616a/GRB 260616B: EP-FXT follow-up observation
  65. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  66. GRB260616C: MAXI/GSC detection
  67. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  68. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  69. EP260616a: EP-WXT detection of a fast X-ray transient
  70. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  71. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  72. GRB 260614B: SVOM/ECLAIRs refined analysis
  73. GRB 260610B: Terskol optical observations
  74. GRB 260614B: SVOM/VT optical afterglow confirmation
  75. GRB 260610B: ALMA detection
  76. GRB 260610B: further Liverpool Telescope optical observations
  77. GRB 260610B / AT2026owq: GRANDMA optical observations
  78. GRB 260610B / AT2026owq: further SAO RAS optical observations
  79. EP260605a: COLIBRÍ optical upper limits
  80. GRB 260610b: Liverpool Telescope optical observations
  81. IceCube-260610A: No candidates from the Zwicky Transient Facility
  82. IceCube-260610A: EP-FXT follow-up observation
  83. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  84. GRB 260610B / AT2026owq: SVOM/VT optical observations
  85. GRB 260610B / AT2026owq: OASDG optical observations
  86. GRB 260610B: IAC-80 Optical observations
  87. GRB 260610B / AT2026owq: SAO RAS optical observations
  88. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  89. EP260610b: GTC likely spectroscopic redshift z = 1.10
  90. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  91. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  92. GRB 260610B / AT2026owq: Early ATLAS observations
  93. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  94. EP260610b: COLIBRÍ optical observations
  95. GRB 260610B: DDOTI optical observations
  96. EP260610b: MAO/AZT-22 optical observations
  97. GRB 260610B: GOTO optical counterpart candidate
  98. EP260610b: SVOM/VT optical confirmation with blue color
  99. GRB 260515A: SOAR optical observations
  100. EP260610b: Gemini North optical counterpart candidate

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