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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

36134 results found.

  1. GRB 260504B: AST3-2 i-band upper limit
  2. GRB 260504B: LCO z-band upper limit
  3. SVOM GRB 260504B: MASTER-OAFA optical observations
  4. GRB 260504B: SVOM detection of a short burst
  5. Fermi GRB 260504A: Global MASTER-Net observations report
  6. GRB 260504A: Fermi GBM Final Real-time Localization
  7. GRB 260503A: Fermi GBM Final Real-time Localization
  8. GRB 260502A: GECAM-B observation of a short burst
  9. GRB 260502A: Fermi GBM Final Localization
  10. GRB 260429B / EP260429a: EP-FXT follow-up observation
  11. GRB 260429B / EP260429a: AstroSat CZTI detection
  12. GRB 260429A: SVOM/GRM observation of a short burst
  13. GRB 260424B: AstroSat CZTI detection
  14. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  15. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  16. GRB 260429A: Fermi GBM Detection
  17. Fermi GRB 260429A: Global MASTER-Net observations report
  18. GRB 260429A: Fermi GBM Final Real-time Localization
  19. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  20. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  21. GRB 260428A: AstroSat CZTI detection
  22. Fermi GRB 260428A: Global MASTER-Net observations report
  23. EP260416a: Mondy and Terskol optical upper limits
  24. GRB 260424B: Glowbug gamma-ray detection of a short burst
  25. GRB 260424B: COLIBRÍ optical upper limit
  26. Konus-Wind detection of GRB 260424B
  27. GRB 260428A: Fermi GBM Final Real-time Localization
  28. GRB 260424C: Fermi GBM Final Localization
  29. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  30. IPN triangulation of GRB 260424B (short)
  31. GRB 260424B: SVOM/GRM detection of a short burst
  32. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  33. GRB 260401A: cubesat Avion detection
  34. GRB 260424A: AstroSat CZTI detection of a long burst
  35. GRB 260421B: Kilonova-Catcher optical afterglow detection
  36. GRB 260421B: Insight-HXMT/HE detection
  37. The EP-WXT trigger 01709258652: Mondy optical observations
  38. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  39. EP260416a: Mondy optical observations
  40. GRB 260421B: SVOM/ECLAIRs refined analysis
  41. GRB 260421B: 3.6m DOT optical observation
  42. EP260416a: ZTSh R band observations
  43. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  44. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  45. GRB 260419A: AstroSat CZTI detection
  46. GRB 260421B: SVOM/GRM observation
  47. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  48. GRB 260421B: EP-FXT follow-up observation
  49. GRB 260421B: J-band upper limit with WINTER
  50. GRB 260421B: LCO optical counterpart detection
  51. GRB 260421B: Fermi GBM Observation
  52. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  53. GRB 260421A: AstroSat CZTI detection
  54. GRB 260412A: SVOM/ECLAIRs refined analysis
  55. GRB 260421B: SVOM/VT optical observations
  56. GRB 260310A: Late-time Chandra X-ray Detection
  57. GRB 260418A: Insight-HXMT/HE detection
  58. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  59. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  60. Fermi GRB 260421C: Global MASTER-Net observations report
  61. GRB 260421C: Fermi GBM Final Real-time Localization
  62. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  63. Fermi GRB 260421B: Global MASTER-Net observations report
  64. GRB 260421B: BOOTES-7 early optical afterglow detection
  65. GRB 260421B: LCO optical afterglow confirmation
  66. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  67. GRB 260421B: TRT optical counterpart detection
  68. GRB 260421B: SVOM detection of a long burst
  69. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  70. GRB 260421B: Fermi GBM Final Real-time Localization
  71. Fermi GRB 260421A: Global MASTER-Net observations report
  72. GRB 260421A: Fermi GBM Final Real-time Localization
  73. GRB 260412A: LCOGT Optical Upper Limits
  74. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  75. EP-WXT trigger 01709260303: KAIT optical observations
  76. GRB 260417A: SVOM/GRM observation
  77. GRB 260419B: Fermi GBM Final Real-time Localization
  78. GRB 260419A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 260417B: Global MASTER-Net observations report
  80. GRB 260418B: Fermi GBM Final Real-time Localization
  81. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  82. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  83. GRB 260418A: Fermi GBM Final Real-time Localization
  84. Fermi GRB 260417A: Global MASTER-Net observations report
  85. Konus-Wind detection of GRB 260411B
  86. GRB 260417B: Fermi GBM Final Real-time Localization
  87. GRB 260417A: AstroSat CZTI detection
  88. IPN triangulation of GRB 260411B
  89. EP-WXT trigger 01709259586: KAIT optical observations
  90. EP260416a: KAIT optical upper limit
  91. GRB 260414A: Insight-HXMT/HE detection
  92. GRB 260417A: Fermi GBM Final Real-time Localization
  93. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  94. GRB 260415B: Glowbug gamma-ray detection
  95. GRB 260411B: Glowbug gamma-ray detection
  96. GRB 260415A: Insight-HXMT/HE detection
  97. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  98. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  99. GRB 260415B: NuSTAR detection of long prompt emission
  100. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow

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