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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"

21793 results found.

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

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