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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"

37549 results found.

  1. GRB 260527A/EP260527a: 6 GHz VLA observations
  2. GRB 260604C: GOTO detections of the optical afterglow
  3. GRB 260604C: Correction to GCN 44828
  4. GRB 260604C: Kilonova-Catcher optical afterglow detection
  5. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. GRB 260604C: Jinshan optical observations
  7. GRB 260604C: Fermi GBM Observation
  8. GRB 260604C: LAST detection of optical counterpart candidate
  9. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  10. Fermi GRB 260604C: Global MASTER-Net observations report
  11. Fermi GRB 260604C: Global MASTER-Net observations report
  12. GRB 260604C: SVOM detection of a long burst
  13. GRB 260604C: Fermi GBM Final Real-time Localization
  14. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  15. GRB 260603A: NOT optical observations
  16. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  17. GRB 260604B: Fermi GBM Final Real-time Localization
  18. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  19. GRB 260604A: Fermi GBM Final Real-time Localization
  20. GRB 260603B: Fermi GBM Final Localization
  21. Konus-Wind detection of GRB 260601B/EP260601a
  22. GRB 260603A: EP-FXT follow-up observation
  23. EP260601a/GRB 260601B: EP-FXT follow-up observation
  24. GRB 260601B / EP260601a: Mondy optical upper limit
  25. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  26. GRB 260603A: Kilonova-Catcher optical upper limit
  27. GRB 260603A: SVOM/VT optical observations
  28. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  29. Fermi trigger No 802141998: Global MASTER-Net observations report
  30. GRB 260601A: SVOM/GRM observation of a short burst
  31. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  32. GRB 260603A: SVOM detection of a burst
  33. GRB 260601B/EP260601a: Insight-HXMT detection
  34. Fermi GRB 260602B: Global MASTER-Net observations report
  35. Fermi GRB 260602B: Global MASTER-Net observations report
  36. GRB 260602B: Fermi GBM Final Localization
  37. GRB 260601A: GECAM-B observation of a short burst
  38. GRB 260601B/EP260601a: J-band upper limit with WINTER
  39. EP260530a/AT 2026nwl: KAIT optical observations
  40. GRB 260602A: Fermi GBM Final Real-time Localization
  41. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  42. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  43. GRB 260601B/EP260601a: SVOM/VT optical observations
  44. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  45. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  46. GRB 260601A: Glowbug gamma-ray detection of a short burst
  47. GRB 260531B: Glowbug gamma-ray detection
  48. GRB 260516D: VLA radio detection
  49. GRB 260601A: Fermi GBM Observation
  50. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  51. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  52. Fermi GRB 260601A: Global MASTER-Net observations report
  53. GRB 260601A: Fermi GBM Final Real-time Localization
  54. GRB 260531B: GECAM-B observation
  55. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  56. GRB 260531C: Fermi GBM Final Localization Correction
  57. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  58. Fermi trigger No 801900520: Global MASTER-Net observations report
  59. GRB 260531B: Fermi GBM Final Real-time Localization
  60. GRB 260531A: MAXI/GSC detection
  61. AT 2026nuz: COLIBRÍ optical observations
  62. IPN triangulation of GRB 260527A / EP260527a
  63. EP260527a/GRB 260527A: further FTW optical and NIR observations
  64. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  65. GRB 260530A: Fermi GBM Final Real-time Localization
  66. GRB 260527A / EP260527a: VLA radio detection
  67. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  68. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  69. GRB 260529A: GOTO tentative optical afterglow candidate
  70. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  71. GRB 260527A/EP260527a: Insight-HXMT detection
  72. Fermi GRB 260529A: Global MASTER-Net observations report
  73. GRB 260529A: Fermi GBM Final Real-time Localization
  74. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  75. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  76. EP260527a / GRB 260527A: NOT optical observations
  77. GRB 260527A/EP260527a: FTW optical and NIR observations
  78. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  79. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  80. EP260527a/GRB 260527A: EP-FXT follow-up observation
  81. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  82. GRB 260526A: GECAM-B observation
  83. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  84. Fermi trigger No 801580882: Global MASTER-Net observations report
  85. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  86. GRB 260525A: AstroSat CZTI detection
  87. Fermi GRB 260526A: Global MASTER-Net observations report
  88. GRB 260526A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260525A: Global MASTER-Net observations report
  90. GRB 260525A: Fermi GBM Final Real-time Localization
  91. GRB 260523B: AstroSat CZTI detection
  92. GRB 260523B: GECAM-B observation
  93. Fermi GRB 260523A: Global MASTER-Net observations report
  94. GRB 260523B: Fermi GBM Final Real-time Localization
  95. GRB 260523A: Fermi GBM Final Real-time Localization
  96. GRB 260522A: Fermi GBM Observation
  97. GRB 260522B: NuSTAR detection of prompt emission
  98. GRB 260522B: Fermi GBM Final Real-time Localization
  99. GRB 260522A: GOTO optical upper limit
  100. Fermi trigger No 801135305: Global MASTER-Net observations report

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