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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"

21782 results found.

  1. IceCube Alert 260709A: Global MASTER-Net observations report
  2. LAT GRB260708.42: Global MASTER-Net observations report
  3. GRB 260706A: SVOM/VT optical upper limits
  4. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  5. GRB 260706A: SVOM/ECLAIRs refined analysis
  6. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  7. GRB 260706A: REM optical/NIR observations
  8. IceCube-260704A: No candidates from the Zwicky Transient Facility
  9. GRB 260705A: SVOM/ECLAIRs refined analysis
  10. IceCube260704A: OHP/T193 optical observations
  11. GRB 260704A: NOT optical upper limits
  12. Fermi GBM Sub-Threshold Detection of GRB 260705A
  13. EP260703a: EP-WXT detection of a fast X-ray transient
  14. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  15. Fermi trigger No 804738310: Global MASTER-Net observations report
  16. Fermi GRB 260703A: Global MASTER-Net observations report
  17. GRB 260610B: VLA detection
  18. GRB 260614B: ATCA Radio Upper Limits
  19. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  20. Fermi trigger No 804552016: Global MASTER-Net observations report
  21. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  22. Fermi GRB 260628A: Global MASTER-Net observations report
  23. EP260628a: EP-WXT detection of a fast X-ray transient
  24. EP260626a: EP-WXT detection of a fast X-ray transient
  25. EP260623a: FTW optical and NIR observations
  26. GRB 260619A: SVOM/ECLAIRs refined analysis
  27. EP260623a: Liverpool Telescope optical observations
  28. EP260623a: WINTER J-band observations
  29. EP260623a: Optical follow-up observations with Kinder
  30. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  31. EP260623a: SVOM/VT optical observations
  32. EP260623a: TRT optical observations
  33. EP260623a: REM optical/NIR afterglow detection
  34. EP 260623a: COLIBRÍ optical observations
  35. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  36. EP260618a: Liverpool Telescope optical observations
  37. GRB 260619A: NOT optical observations
  38. GRB 260618B: LCO optical observations
  39. EP260618a: JinShan optical observations
  40. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  41. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  42. GRB 260619A: SVOM/VT optical counterpart confirmation
  43. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  44. GRB 260618B: SVOM/VT optical candidate
  45. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  46. EP260618a: OHP/T193 optical observations
  47. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  48. GRB 260619A: Kilonova-Catcher optical upper limit
  49. EP260618a: EP-FXT follow-up observation
  50. EP260618a: COLIBRÍ optical counterpart candidate
  51. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  52. EP260618a: EP-WXT detection of an X-ray transient
  53. GRB 260610B: AbAO optical observations
  54. EP260616a/GRB 260616B: EP-FXT follow-up observation
  55. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  56. GRB260616C: MAXI/GSC detection
  57. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  58. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  59. EP260616a: EP-WXT detection of a fast X-ray transient
  60. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  61. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  62. GRB 260614B: SVOM/ECLAIRs refined analysis
  63. GRB 260610B: Terskol optical observations
  64. GRB 260614B: SVOM/VT optical afterglow confirmation
  65. GRB 260610B: ALMA detection
  66. GRB 260610B: further Liverpool Telescope optical observations
  67. GRB 260610B / AT2026owq: GRANDMA optical observations
  68. GRB 260610B / AT2026owq: further SAO RAS optical observations
  69. EP260605a: COLIBRÍ optical upper limits
  70. GRB 260610b: Liverpool Telescope optical observations
  71. IceCube-260610A: No candidates from the Zwicky Transient Facility
  72. IceCube-260610A: EP-FXT follow-up observation
  73. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  74. GRB 260610B / AT2026owq: SVOM/VT optical observations
  75. GRB 260610B / AT2026owq: OASDG optical observations
  76. GRB 260610B: IAC-80 Optical observations
  77. GRB 260610B / AT2026owq: SAO RAS optical observations
  78. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  79. EP260610b: GTC likely spectroscopic redshift z = 1.10
  80. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  81. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  82. GRB 260610B / AT2026owq: Early ATLAS observations
  83. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  84. EP260610b: COLIBRÍ optical observations
  85. GRB 260610B: DDOTI optical observations
  86. EP260610b: MAO/AZT-22 optical observations
  87. GRB 260610B: GOTO optical counterpart candidate
  88. EP260610b: SVOM/VT optical confirmation with blue color
  89. GRB 260515A: SOAR optical observations
  90. EP260610b: Gemini North optical counterpart candidate
  91. GRB 260604C: SVOM/ECLAIRs refined analysis
  92. GRB 260608A: SVOM/ECLAIRs refined analysis
  93. GRB 260604C: further SAO RAS optical observations
  94. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  95. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  96. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  97. GRB 260604C: SVOM/C-GFT upper limit
  98. GRB 260607A: TRT optical observations
  99. GRB 260604C: GRANDMA further observations
  100. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong

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