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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"

22062 results found.

  1. GRB 260705A: ATCA radio observations
  2. GRB 260619A: SVOM/VT continuous optical observations
  3. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  4. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  5. EP260623a: KAIT optical observations
  6. GRB 260708A: GRANDMA Optical Observations
  7. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  8. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  9. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  10. GRB 260708A: LCO optical observations
  11. EP260711a: Einstein Probe detection of an X-ray transient
  12. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  13. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  14. GRB 260704A: SVOM/ECLAIRs refined analysis
  15. GRB 260706A : GRANDMA Upper limits
  16. GRB 260708A: Kilonova-Catcher optical afterglow detection
  17. IceCube-260708A: One candidate from the Zwicky Transient Facility
  18. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  19. IceCube Alert 260709A: Global MASTER-Net observations report
  20. LAT GRB260708.42: Global MASTER-Net observations report
  21. GRB 260706A: SVOM/VT optical upper limits
  22. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  23. GRB 260706A: SVOM/ECLAIRs refined analysis
  24. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  25. GRB 260706A: REM optical/NIR observations
  26. IceCube-260704A: No candidates from the Zwicky Transient Facility
  27. GRB 260705A: SVOM/ECLAIRs refined analysis
  28. IceCube260704A: OHP/T193 optical observations
  29. GRB 260704A: NOT optical upper limits
  30. EP260703a: EP-WXT detection of a fast X-ray transient
  31. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  32. Fermi trigger No 804738310: Global MASTER-Net observations report
  33. Fermi GRB 260703A: Global MASTER-Net observations report
  34. GRB 260610B: VLA detection
  35. GRB 260614B: ATCA Radio Upper Limits
  36. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  37. Fermi trigger No 804552016: Global MASTER-Net observations report
  38. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  39. Fermi GRB 260628A: Global MASTER-Net observations report
  40. EP260628a: EP-WXT detection of a fast X-ray transient
  41. EP260626a: EP-WXT detection of a fast X-ray transient
  42. Konus-Wind detection of GRB 260623B / EP260623a
  43. EP260623a: TNG NIR afterglow detection
  44. EP260623a: FTW optical and NIR observations
  45. GRB 260619A: SVOM/ECLAIRs refined analysis
  46. EP260623a: Liverpool Telescope optical observations
  47. Konus-Wind detection of GRB 260618B
  48. EP260623a: WINTER J-band observations
  49. EP260623a: Optical follow-up observations with Kinder
  50. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  51. EP260623a: SVOM/VT optical observations
  52. EP260623a: TRT optical observations
  53. EP260623a: REM optical/NIR afterglow detection
  54. EP 260623a: COLIBRÍ optical observations
  55. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  56. EP260618a: Liverpool Telescope optical observations
  57. GRB 260619A: NOT optical observations
  58. GRB 260618B: LCO optical observations
  59. EP260618a: JinShan optical observations
  60. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  61. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  62. GRB 260619A: SVOM/VT optical counterpart confirmation
  63. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  64. GRB 260618B: SVOM/VT optical candidate
  65. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  66. EP260618a: OHP/T193 optical observations
  67. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  68. GRB 260619A: Kilonova-Catcher optical upper limit
  69. EP260618a: EP-FXT follow-up observation
  70. EP260618a: COLIBRÍ optical counterpart candidate
  71. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  72. EP260618a: EP-WXT detection of an X-ray transient
  73. GRB 260610B: AbAO optical observations
  74. EP260616a/GRB 260616B: EP-FXT follow-up observation
  75. Konus-Wind detection of GRB 260616B/EP260616a
  76. Konus-Wind detection of GRB 260616A
  77. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  79. GRB260616C: MAXI/GSC detection
  80. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  81. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  82. EP260616a: EP-WXT detection of a fast X-ray transient
  83. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  84. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  85. GRB 260614B: SVOM/ECLAIRs refined analysis
  86. GRB 260610B: Terskol optical observations
  87. GRB 260614B: SVOM/VT optical afterglow confirmation
  88. GRB 260610B: ALMA detection
  89. GRB 260610B: further Liverpool Telescope optical observations
  90. GRB 260610B / AT2026owq: GRANDMA optical observations
  91. GRB 260610B / AT2026owq: further SAO RAS optical observations
  92. EP260605a: COLIBRÍ optical upper limits
  93. GRB 260610b: Liverpool Telescope optical observations
  94. IceCube-260610A: No candidates from the Zwicky Transient Facility
  95. IceCube-260610A: EP-FXT follow-up observation
  96. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  97. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  98. GRB 260610B / AT2026owq: SVOM/VT optical observations
  99. GRB 260610B / AT2026owq: OASDG optical observations
  100. GRB 260610B: IAC-80 Optical observations

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