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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"

16109 results found.

  1. GRB 260708A: GRANDMA Optical Observations
  2. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  3. GRB 260708A: LCO optical observations
  4. GRB 260709A: SVOM/GRM detection
  5. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  6. GRB 260708A: Glowbug gamma-ray detection
  7. GRB 260706A : GRANDMA Upper limits
  8. GRB 260708A: Kilonova-Catcher optical afterglow detection
  9. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  10. GRB 260705B: SVOM/GRM observation
  11. GRB 260706A: SVOM/VT optical upper limits
  12. EP260707a (by EP-FXT): NOT optical upper limit
  13. EP260707a is not a real source
  14. EP260707a: LCOGT Optical Upper Limit
  15. EP260707a: TRT optical upper limit
  16. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  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 260706A: LCO optical upper limit
  21. GRB 260706A: SVOM detection of a burst
  22. IceCube260704A: OHP/T193 optical observations
  23. GRB 260705A: LCO optical upper limits
  24. GRB 260704A: NOT optical upper limits
  25. GRB 260705A: SVOM detection of a burst
  26. GRB 260629A: SVOM/GRM observation of a short burst
  27. GRB 260610B: VLA detection
  28. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  29. EP260626a: further Liverpool Telescope optical upper limits
  30. EP260626a: EP-FXT follow-up observation
  31. EP260626a: COLIBRÍ optical upper limit
  32. EP260623a: FTW optical and NIR observations
  33. EP260623a: Liverpool Telescope optical observations
  34. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  35. EP260623a: WINTER J-band observations
  36. EP260623a: Optical follow-up observations with Kinder
  37. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  38. EP260623a: SVOM/VT optical observations
  39. EP260623a: TRT optical observations
  40. EP260623a: REM optical/NIR afterglow detection
  41. EP 260623a: COLIBRÍ optical observations
  42. EP260623a: OSIRIS+/GTC redshift z = 0.703
  43. EP260623a: Las Cumbres discovery of the optical counterpart
  44. GRB 260614B: EP-FXT follow-up observation
  45. EP260618a: Liverpool Telescope optical observations
  46. GRB 260619A: NOT optical observations
  47. GRB 260618B: LCO optical observations
  48. EP260618a: JinShan optical observations
  49. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  50. GRB 260619A: TRT optical counterpart confirmation
  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. GRB 260618B: SVOM/VT optical candidate
  55. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  56. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  57. GRB 260616A: SVOM/GRM observation
  58. EP260618a: OHP/T193 optical observations
  59. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  60. GRB 260619A: Kilonova-Catcher optical upper limit
  61. EP260618a: EP-FXT follow-up observation
  62. EP260618a: LCO optical counterpart confirmation
  63. EP260618a: COLIBRÍ optical counterpart candidate
  64. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  65. GRB 260610B: AbAO optical observations
  66. EP260616a/GRB 260616B: EP-FXT follow-up observation
  67. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  68. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  69. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  70. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  71. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  72. GRB 260610B: Terskol optical observations
  73. GRB 260610B: SVOM/GRM observation
  74. GRB 260614B: SVOM/VT optical afterglow confirmation
  75. GRB 260610B: ALMA detection
  76. GRB 260614B: SVOM/VT optical candidate from VHF data
  77. GRB 260611B: SVOM/GRM detection
  78. GRB 260610B: further Liverpool Telescope optical observations
  79. GRB 260610B: Fermi GBM Observation
  80. GRB 260610B / AT2026owq: GRANDMA optical observations
  81. GRB 260610B / AT2026owq: further SAO RAS optical observations
  82. EP260605a: COLIBRÍ optical upper limits
  83. GRB 260610b: Liverpool Telescope optical observations
  84. EP260610b: Liverpool Telescope optical upper limits
  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. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  92. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  93. GRB 260610B / AT2026owq: Early ATLAS observations
  94. GRB 260610B: TRT optical observation
  95. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  96. EP260610b: COLIBRÍ optical observations
  97. GRB 260610B: DDOTI optical observations
  98. EP260610b: MAO/AZT-22 optical observations
  99. GRB 260610B: GOTO optical counterpart candidate
  100. EP260610b: NOT optical observation

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