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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"

37955 results found.

  1. Fermi GRB 260604C: Global MASTER-Net observations report
  2. Fermi GRB 260604C: Global MASTER-Net observations report
  3. SVOM GRB260604.85: Global MASTER-Net observations report
  4. GRB 260604C: SVOM detection of a long burst
  5. GRB 260604C: Fermi GBM Final Real-time Localization
  6. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  7. GRB 260603A: NOT optical observations
  8. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  9. GRB 260604B: Fermi GBM Final Real-time Localization
  10. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  11. EP260603a: Global MASTER-Net observations report
  12. GRB 260604A: Fermi GBM Final Real-time Localization
  13. GRB 260603B: Fermi GBM Final Localization
  14. Konus-Wind detection of GRB 260601B/EP260601a
  15. GRB 260603A: EP-FXT follow-up observation
  16. EP260601a/GRB 260601B: EP-FXT follow-up observation
  17. GRB 260601B / EP260601a: Mondy optical upper limit
  18. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  19. GRB 260603A: Kilonova-Catcher optical upper limit
  20. GRB 260603A: SVOM/VT optical observations
  21. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  22. Fermi trigger No 802141998: Global MASTER-Net observations report
  23. GRB 260601A: SVOM/GRM observation of a short burst
  24. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  25. SVOM GRB260603.23: Global MASTER-Net observations report
  26. GRB 260603A: SVOM detection of a burst
  27. GRB 260601B/EP260601a: Insight-HXMT detection
  28. Fermi GRB 260602B: Global MASTER-Net observations report
  29. Fermi GRB 260602B: Global MASTER-Net observations report
  30. GRB 260602B: Fermi GBM Final Localization
  31. GRB 260601A: GECAM-B observation of a short burst
  32. GRB 260601B/EP260601a: J-band upper limit with WINTER
  33. EP260530a/AT 2026nwl: KAIT optical observations
  34. GRB 260602A: Fermi GBM Final Real-time Localization
  35. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  36. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  37. GRB 260601B/EP260601a: SVOM/VT optical observations
  38. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  39. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  40. GRB 260601A: Glowbug gamma-ray detection of a short burst
  41. GRB 260531B: Glowbug gamma-ray detection
  42. GRB 260516D: VLA radio detection
  43. GRB 260601A: Fermi GBM Observation
  44. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  45. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  46. Fermi GRB 260601A: Global MASTER-Net observations report
  47. GRB 260601A: Fermi GBM Final Real-time Localization
  48. GRB 260531B: GECAM-B observation
  49. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  50. GRB 260531C: Fermi GBM Final Localization Correction
  51. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  52. Fermi trigger No 801900520: Global MASTER-Net observations report
  53. GRB 260531B: Fermi GBM Final Real-time Localization
  54. GRB 260531A: MAXI/GSC detection
  55. AT 2026nuz: COLIBRÍ optical observations
  56. IPN triangulation of GRB 260527A / EP260527a
  57. EP260527a/GRB 260527A: further FTW optical and NIR observations
  58. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  59. GRB 260530A: Fermi GBM Final Real-time Localization
  60. GRB 260527A / EP260527a: VLA radio detection
  61. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  62. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  63. GRB 260529A: GOTO tentative optical afterglow candidate
  64. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  65. GRB 260527A/EP260527a: Insight-HXMT detection
  66. Fermi GRB 260529A: Global MASTER-Net observations report
  67. GRB 260529A: Fermi GBM Final Real-time Localization
  68. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  69. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  70. EP260527a / GRB 260527A: NOT optical observations
  71. GRB 260527A/EP260527a: FTW optical and NIR observations
  72. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  73. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  74. EP260527a/GRB 260527A: EP-FXT follow-up observation
  75. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  76. GRB 260526A: GECAM-B observation
  77. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  78. Fermi trigger No 801580882: Global MASTER-Net observations report
  79. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  80. GRB 260525A: AstroSat CZTI detection
  81. Fermi GRB 260526A: Global MASTER-Net observations report
  82. GRB 260526A: Fermi GBM Final Real-time Localization
  83. Fermi GRB 260525A: Global MASTER-Net observations report
  84. GRB 260525A: Fermi GBM Final Real-time Localization
  85. GRB 260523B: AstroSat CZTI detection
  86. GRB 260523B: GECAM-B observation
  87. Fermi GRB 260523A: Global MASTER-Net observations report
  88. GRB 260523B: Fermi GBM Final Real-time Localization
  89. GRB 260523A: Fermi GBM Final Real-time Localization
  90. GRB 260522A: Fermi GBM Observation
  91. GRB 260522B: NuSTAR detection of prompt emission
  92. GRB 260522B: Fermi GBM Final Real-time Localization
  93. GRB 260522A: GOTO optical upper limit
  94. Fermi trigger No 801135305: Global MASTER-Net observations report
  95. Fermi GRB 260522A: Global MASTER-Net observations report
  96. GRB 260522A: Fermi-LAT detection
  97. GRB 260519C: SVOM/GRM observation
  98. GRB 260522A: Fermi GBM Final Real-time Localization
  99. GRB 260511A: iTelescope T-75 optical detection
  100. GRB 260520B: SVOM/GRM observation

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