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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"

3103 results found.

  1. GRB 260827A: Fermi GBM Final Real-time Localization
  2. IceCube Alert 260825A: Global MASTER-Net observations report
  3. The EP-WXT trigger 01709287395 is likely a flaring star
  4. EP260806a: SVOM/ECLAIRs detection through targeted search
  5. EP260806a: NUTTELA-TAO optical observations
  6. GRB 260810A: AstroSat CZTI detection of a long burst
  7. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  8. GRB 260808A: Fermi GBM Final Real-time Localization
  9. SN 2026stf / GRB 260708A: ATLAS forced photometry
  10. GRB 260803A: Fermi GBM Final Real-time Localization
  11. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  12. GRB 260731A: AstroSat CZTI detection of a long burst
  13. GRB 260730B: AstroSat CZTI detection
  14. GRB 260727A: AstroSat CZTI detection
  15. Fermi GRB 260726A: Global MASTER-Net observations report
  16. GRB 260723A: Fermi GBM Final Localization
  17. GRB 260718A: SVOM/VT optical upper limits
  18. SVOM sb26071506: Global MASTER-Net observations report
  19. GRB 260710A: AstroSat CZTI detection
  20. GRB 260709A: AstroSat CZTI detection
  21. GRB 260714B: AstroSat CZTI detection
  22. GRB 260714B: Fermi GBM Final Real-time Localization
  23. GRB 260708A: GRANDMA Optical Observations
  24. GRB 260705C: AstroSat CZTI detection
  25. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  26. LAT GRB260708.42: Global MASTER-Net observations report
  27. GRB 260706A: SVOM/VT optical upper limits
  28. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  29. GRB 260707A: Fermi GBM Final Real-time Localization
  30. IPN triangulation of GRB 260627A
  31. GRB 260629A: AstroSat CZTI detection
  32. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  33. Fermi trigger No 804552016: Global MASTER-Net observations report
  34. GRB 260616B: AstroSat CZTI detection
  35. GRB 260616A: AstroSat CZTI detection
  36. GRB 260506B: cubesat Avion detection
  37. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  38. GRB260616C: MAXI/GSC detection
  39. GRB 260614A: AstroSat CZTI detection
  40. GRB 260603C: AstroSat CZTI detection
  41. EP260605a: COLIBRÍ optical upper limits
  42. GRB 260604C: AstroSat CZTI detection
  43. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  44. GRB 260607B: AstroSat CZTI detection
  45. The EP-WXT trigger 01709267001 is likely a flaring star
  46. GRB 260601B / EP260601a: AstroSat CZTI detection
  47. EP260603a: Global MASTER-Net observations report
  48. Fermi GRB 260602B: Global MASTER-Net observations report
  49. Fermi GRB 260602B: Global MASTER-Net observations report
  50. GRB 260602A: Fermi GBM Final Real-time Localization
  51. Fermi trigger No 801900520: Global MASTER-Net observations report
  52. GRB 260531A: MAXI/GSC detection
  53. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  54. GRB 260526A: GECAM-B observation
  55. GRB 260525A: AstroSat CZTI detection
  56. Fermi GRB 260526A: Global MASTER-Net observations report
  57. GRB 260525A: Fermi GBM Final Real-time Localization
  58. GRB 260523B: AstroSat CZTI detection
  59. GRB 260511A: iTelescope T-75 optical detection
  60. GRB 260518A: AstroSat CZTI detection of a long burst
  61. GRB 260515A: further Liverpool Telescope observations
  62. Fermi GRB 260516C: Global MASTER-Net observations report
  63. GRB 260515A: Liverpool Telescope optical detection
  64. GRB 260515A: LCO optical observations
  65. SVOM GRB 260515A: Global MASTER-Net observations report
  66. EP260514a: Global MASTER-Net observations report
  67. GRB 260512A: AstroSat CZTI detection
  68. GRB 260514A: Fermi GBM Final Real-time Localization
  69. Fermi GRB 260512A: Global MASTER-Net observations report
  70. Konus-Wind detection of GRB 260511B
  71. GRB 260511B: AstroSat CZTI detection
  72. GRB 260510C: AstroSat CZTI detection
  73. GRB 260511A: SVOM/VT optical observation with VHF data
  74. Fermi GRB 260511A: Global MASTER-Net observations report
  75. GRB 260510C: MAXI/GSC detection
  76. SVOM GRB 260509A: MASTER-OAFA optical observation
  77. GRB 260504B: AstroSat CZTI detection
  78. EP260502a is likely a flaring star
  79. IceCube Alert 260505A: Global MASTER-Net observations report
  80. GRB 260430B: AstroSat CZTI detection of a long burst
  81. SVOM GRB 260504B: MASTER-OAFA optical observations
  82. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  83. GRB 260429B / EP260429a: AstroSat CZTI detection
  84. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  85. GRB 260424B: AstroSat CZTI detection
  86. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  87. GRB 260428A: AstroSat CZTI detection
  88. Fermi GRB 260428A: Global MASTER-Net observations report
  89. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  90. IceCube Alert 260425A: Global MASTER-Net observations report
  91. GRB 260424A: AstroSat CZTI detection of a long burst
  92. EP260416a: ZTSh R band observations
  93. GRB 260419A: AstroSat CZTI detection
  94. GRB 260421A: AstroSat CZTI detection
  95. GRB 260310A: Late-time Chandra X-ray Detection
  96. Fermi GRB 260421C: Global MASTER-Net observations report
  97. Fermi GRB 260421B: Global MASTER-Net observations report
  98. Fermi trigger No 798275385: Global MASTER-Net observations report
  99. EP260417a: Global MASTER-Net observations report
  100. Fermi GRB 260417A: Global MASTER-Net observations report

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