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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"

3757 results found.

  1. GRB 260506A: Fermi GBM Final Real-time Localization
  2. Fermi GRB 260504A: Global MASTER-Net observations report
  3. Fermi GRB 260429A: Global MASTER-Net observations report
  4. GRB 260428A: AstroSat CZTI detection
  5. Fermi GRB 260428A: Global MASTER-Net observations report
  6. GRB 260424B: COLIBRÍ optical upper limit
  7. GRB 260428A: Fermi GBM Final Real-time Localization
  8. GRB 260401A: cubesat Avion detection
  9. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  10. EP260416a: Mondy optical observations
  11. GRB 260419A: AstroSat CZTI detection
  12. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  13. Fermi GRB 260421C: Global MASTER-Net observations report
  14. Fermi GRB 260421B: Global MASTER-Net observations report
  15. GRB 260421B: BOOTES-7 early optical afterglow detection
  16. EP260417a: Global MASTER-Net observations report
  17. Fermi GRB 260417A: Global MASTER-Net observations report
  18. EP260416a: Global MASTER-Net observations report
  19. GRB 260415B: NuSTAR detection of long prompt emission
  20. EP260321a: SVOM/VT optical observations and color changes around peak
  21. GRB 260411A: Fermi GBM Final Real-time Localization
  22. EP260405a: GMOS-N optical upper limits
  23. EP260405a: SVOM/VT optical upper limits
  24. Fermi trigger No 797039833: Global MASTER-Net observations report
  25. EP260403a: LCO optical counterpart detection
  26. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  27. EP260329b: GOTO detection of optical counterpart
  28. Fermi trigger No 796485221: Global MASTER-Net observations report
  29. GRB 260327A: Insight-HXMT/HE detection
  30. GRID detection of GRB 260326A
  31. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  32. GRB 260327A: AstroSat CZTI detection of a long burst
  33. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  34. GRB 260326A: Fermi GBM Final Real-time Localization
  35. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  36. IceCube-260315A: COLIBRÍ optical observations
  37. EP260314a: Global MASTER-Net observations report
  38. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  39. Fermi GRB 260314A: Global MASTER-Net observations report
  40. Fermi GRB 260313A: Global MASTER-Net observations report
  41. GRB 260313A: Fermi GBM Final Real-time Localization
  42. Fermi GRB 260311B: Global MASTER-Net observations report
  43. Fermi GRB 260310B: Global MASTER-Net observations report
  44. GRB 260307B: Mephisto optical upper limits
  45. Fermi GRB 260307A: Global MASTER-Net observations report
  46. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  47. GRB 260304A: AstroSat CZTI detection of a long burst
  48. GRB 260208A: TERI Gamma-ray detection
  49. EP260227a: Mondy optical observations
  50. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. EP260227A: 3.6m DOT optical afterglow detection
  52. EP260227a: Liverpool Telescope optical observations
  53. EP260227a: LCOGT Optical Observations
  54. EP260227a: Thai National Telescope observations
  55. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  56. EP260227a: Liverpool Telescope observations
  57. EP260227a: COLIBRÍ optical observations
  58. EP260227a: NOT optical observations
  59. EP260227a: Global MASTER-Net observations report
  60. LAT GRB260226.44: Global MASTER-Net observations report
  61. GRB 260225A: EP-FXT follow-up observation
  62. GRB 260223A: SVOM/VT optical observation
  63. Fermi GRB 260223A: Global MASTER-Net observations report
  64. EP260221a: Global MASTER-Net observations report
  65. EP-WXT01709258519: Xinglong optical upper limit
  66. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  67. IceCube Alert 260217A: Global MASTER-Net observations report
  68. sb26021801: SVOM detection of a long faint X-ray transient
  69. EP260214b: GROWTH-India Telescope optical upper limit
  70. GRB 260212A: AstroSat CZTI detection
  71. GRB 260211A: SVOM detection of a burst
  72. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  73. EP260210a: Global MASTER-Net observations report
  74. Fermi GRB 260209A: Global MASTER-Net observations report
  75. GRB 260208A: 1.3m DFOT optical detection
  76. Fermi GRB 260208A: Global MASTER-Net observations report
  77. GRB 260208A: Fermi GBM Final Real-time Localization
  78. Fermi GBM Sub-Threshold Detection of GRB 260204A
  79. GRB 260204A: SVOM detection of a burst
  80. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  81. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. Fermi GRB 260129A: Global MASTER-Net observations report
  83. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  84. EP260128a: Liverpool Telescope optical observations and possible counterpart
  85. EP260128a: Global MASTER-Net observations report
  86. Fermi GRB 260127A: Global MASTER-Net observations report
  87. GRB 260127A: COLIBRÍ optical observations
  88. GRB 260127B: GOTO candidate optical counterpart
  89. Fermi GRB 260125B: Global MASTER-Net observations report
  90. SVOM GRB260121.06: Global MASTER-Net observations report
  91. GRB 260101A: 239Alferov CubeSat detection
  92. Fermi trigger No 790601190: Global MASTER-Net observations report
  93. EP260119a: Global MASTER-Net observations report
  94. GRB 260110A: SVOM detection of a burst through offline search
  95. SVOM GRB260117.82: Global MASTER-Net observations report
  96. Swift triggered on the HMXB 1A 1118-61
  97. GRB 251222A: radio detection with the VLA
  98. Swift GRB 260114A: Global MASTER-Net observations report
  99. Fermi GRB 260105A: Global MASTER-Net observations report
  100. Fermi GRB 260105B: Global MASTER-Net observations report

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