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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"

3104 results found.

  1. GRB 260825A: AstroSat CZTI detection
  2. GRB 260827A: Fermi GBM Final Real-time Localization
  3. IceCube Alert 260825A: Global MASTER-Net observations report
  4. The EP-WXT trigger 01709287395 is likely a flaring star
  5. EP260806a: SVOM/ECLAIRs detection through targeted search
  6. EP260806a: NUTTELA-TAO optical observations
  7. GRB 260810A: AstroSat CZTI detection of a long burst
  8. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  9. GRB 260808A: Fermi GBM Final Real-time Localization
  10. SN 2026stf / GRB 260708A: ATLAS forced photometry
  11. GRB 260803A: Fermi GBM Final Real-time Localization
  12. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  13. GRB 260731A: AstroSat CZTI detection of a long burst
  14. GRB 260730B: AstroSat CZTI detection
  15. GRB 260727A: AstroSat CZTI detection
  16. Fermi GRB 260726A: Global MASTER-Net observations report
  17. GRB 260723A: Fermi GBM Final Localization
  18. GRB 260718A: SVOM/VT optical upper limits
  19. SVOM sb26071506: Global MASTER-Net observations report
  20. GRB 260710A: AstroSat CZTI detection
  21. GRB 260709A: AstroSat CZTI detection
  22. GRB 260714B: AstroSat CZTI detection
  23. GRB 260714B: Fermi GBM Final Real-time Localization
  24. GRB 260708A: GRANDMA Optical Observations
  25. GRB 260705C: AstroSat CZTI detection
  26. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  27. LAT GRB260708.42: Global MASTER-Net observations report
  28. GRB 260706A: SVOM/VT optical upper limits
  29. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  30. GRB 260707A: Fermi GBM Final Real-time Localization
  31. IPN triangulation of GRB 260627A
  32. GRB 260629A: AstroSat CZTI detection
  33. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  34. Fermi trigger No 804552016: Global MASTER-Net observations report
  35. GRB 260616B: AstroSat CZTI detection
  36. GRB 260616A: AstroSat CZTI detection
  37. GRB 260506B: cubesat Avion detection
  38. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  39. GRB260616C: MAXI/GSC detection
  40. GRB 260614A: AstroSat CZTI detection
  41. GRB 260603C: AstroSat CZTI detection
  42. EP260605a: COLIBRÍ optical upper limits
  43. GRB 260604C: AstroSat CZTI detection
  44. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  45. GRB 260607B: AstroSat CZTI detection
  46. The EP-WXT trigger 01709267001 is likely a flaring star
  47. GRB 260601B / EP260601a: AstroSat CZTI detection
  48. EP260603a: Global MASTER-Net observations report
  49. Fermi GRB 260602B: Global MASTER-Net observations report
  50. Fermi GRB 260602B: Global MASTER-Net observations report
  51. GRB 260602A: Fermi GBM Final Real-time Localization
  52. Fermi trigger No 801900520: Global MASTER-Net observations report
  53. GRB 260531A: MAXI/GSC detection
  54. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  55. GRB 260526A: GECAM-B observation
  56. GRB 260525A: AstroSat CZTI detection
  57. Fermi GRB 260526A: Global MASTER-Net observations report
  58. GRB 260525A: Fermi GBM Final Real-time Localization
  59. GRB 260523B: AstroSat CZTI detection
  60. GRB 260511A: iTelescope T-75 optical detection
  61. GRB 260518A: AstroSat CZTI detection of a long burst
  62. GRB 260515A: further Liverpool Telescope observations
  63. Fermi GRB 260516C: Global MASTER-Net observations report
  64. GRB 260515A: Liverpool Telescope optical detection
  65. GRB 260515A: LCO optical observations
  66. SVOM GRB 260515A: Global MASTER-Net observations report
  67. EP260514a: Global MASTER-Net observations report
  68. GRB 260512A: AstroSat CZTI detection
  69. GRB 260514A: Fermi GBM Final Real-time Localization
  70. Fermi GRB 260512A: Global MASTER-Net observations report
  71. Konus-Wind detection of GRB 260511B
  72. GRB 260511B: AstroSat CZTI detection
  73. GRB 260510C: AstroSat CZTI detection
  74. GRB 260511A: SVOM/VT optical observation with VHF data
  75. Fermi GRB 260511A: Global MASTER-Net observations report
  76. GRB 260510C: MAXI/GSC detection
  77. SVOM GRB 260509A: MASTER-OAFA optical observation
  78. GRB 260504B: AstroSat CZTI detection
  79. EP260502a is likely a flaring star
  80. IceCube Alert 260505A: Global MASTER-Net observations report
  81. GRB 260430B: AstroSat CZTI detection of a long burst
  82. SVOM GRB 260504B: MASTER-OAFA optical observations
  83. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  84. GRB 260429B / EP260429a: AstroSat CZTI detection
  85. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  86. GRB 260424B: AstroSat CZTI detection
  87. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  88. GRB 260428A: AstroSat CZTI detection
  89. Fermi GRB 260428A: Global MASTER-Net observations report
  90. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  91. IceCube Alert 260425A: Global MASTER-Net observations report
  92. GRB 260424A: AstroSat CZTI detection of a long burst
  93. EP260416a: ZTSh R band observations
  94. GRB 260419A: AstroSat CZTI detection
  95. GRB 260421A: AstroSat CZTI detection
  96. GRB 260310A: Late-time Chandra X-ray Detection
  97. Fermi GRB 260421C: Global MASTER-Net observations report
  98. Fermi GRB 260421B: Global MASTER-Net observations report
  99. Fermi trigger No 798275385: Global MASTER-Net observations report
  100. EP260417a: Global MASTER-Net observations report

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