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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"

3658 results found.

  1. GRB 260507A: Fermi GBM Final Real-time Localization
  2. GRB 260506A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 260504A: Global MASTER-Net observations report
  4. Fermi GRB 260429A: Global MASTER-Net observations report
  5. GRB 260428A: AstroSat CZTI detection
  6. Fermi GRB 260428A: Global MASTER-Net observations report
  7. GRB 260424B: COLIBRÍ optical upper limit
  8. GRB 260428A: Fermi GBM Final Real-time Localization
  9. GRB 260401A: cubesat Avion detection
  10. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  11. EP260416a: Mondy optical observations
  12. GRB 260419A: AstroSat CZTI detection
  13. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  14. Fermi GRB 260421C: Global MASTER-Net observations report
  15. Fermi GRB 260421B: Global MASTER-Net observations report
  16. GRB 260421B: BOOTES-7 early optical afterglow detection
  17. EP260417a: Global MASTER-Net observations report
  18. Fermi GRB 260417A: Global MASTER-Net observations report
  19. EP260416a: Global MASTER-Net observations report
  20. GRB 260415B: NuSTAR detection of long prompt emission
  21. EP260321a: SVOM/VT optical observations and color changes around peak
  22. GRB 260411A: Fermi GBM Final Real-time Localization
  23. EP260405a: GMOS-N optical upper limits
  24. EP260405a: SVOM/VT optical upper limits
  25. Fermi trigger No 797039833: Global MASTER-Net observations report
  26. EP260403a: LCO optical counterpart detection
  27. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  28. EP260329b: GOTO detection of optical counterpart
  29. Fermi trigger No 796485221: Global MASTER-Net observations report
  30. GRB 260327A: Insight-HXMT/HE detection
  31. GRID detection of GRB 260326A
  32. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  33. GRB 260327A: AstroSat CZTI detection of a long burst
  34. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  35. GRB 260326A: Fermi GBM Final Real-time Localization
  36. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  37. IceCube-260315A: COLIBRÍ optical observations
  38. EP260314a: Global MASTER-Net observations report
  39. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  40. Fermi GRB 260314A: Global MASTER-Net observations report
  41. Fermi GRB 260313A: Global MASTER-Net observations report
  42. GRB 260313A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 260311B: Global MASTER-Net observations report
  44. Fermi GRB 260310B: Global MASTER-Net observations report
  45. GRB 260307B: Mephisto optical upper limits
  46. Fermi GRB 260307A: Global MASTER-Net observations report
  47. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  48. GRB 260304A: AstroSat CZTI detection of a long burst
  49. GRB 260208A: TERI Gamma-ray detection
  50. EP260227a: Mondy optical observations
  51. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  52. EP260227A: 3.6m DOT optical afterglow detection
  53. EP260227a: Liverpool Telescope optical observations
  54. EP260227a: LCOGT Optical Observations
  55. EP260227a: Thai National Telescope observations
  56. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  57. EP260227a: Liverpool Telescope observations
  58. EP260227a: COLIBRÍ optical observations
  59. EP260227a: NOT optical observations
  60. EP260227a: Global MASTER-Net observations report
  61. LAT GRB260226.44: Global MASTER-Net observations report
  62. GRB 260225A: EP-FXT follow-up observation
  63. GRB 260223A: SVOM/VT optical observation
  64. Fermi GRB 260223A: Global MASTER-Net observations report
  65. EP260221a: Global MASTER-Net observations report
  66. EP-WXT01709258519: Xinglong optical upper limit
  67. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  68. IceCube Alert 260217A: Global MASTER-Net observations report
  69. sb26021801: SVOM detection of a long faint X-ray transient
  70. EP260214b: GROWTH-India Telescope optical upper limit
  71. GRB 260212A: AstroSat CZTI detection
  72. GRB 260211A: SVOM detection of a burst
  73. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  74. EP260210a: Global MASTER-Net observations report
  75. Fermi GRB 260209A: Global MASTER-Net observations report
  76. GRB 260208A: 1.3m DFOT optical detection
  77. Fermi GRB 260208A: Global MASTER-Net observations report
  78. GRB 260208A: Fermi GBM Final Real-time Localization
  79. Fermi GBM Sub-Threshold Detection of GRB 260204A
  80. GRB 260204A: SVOM detection of a burst
  81. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  82. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  83. Fermi GRB 260129A: Global MASTER-Net observations report
  84. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  85. EP260128a: Liverpool Telescope optical observations and possible counterpart
  86. EP260128a: Global MASTER-Net observations report
  87. Fermi GRB 260127A: Global MASTER-Net observations report
  88. GRB 260127A: COLIBRÍ optical observations
  89. GRB 260127B: GOTO candidate optical counterpart
  90. Fermi GRB 260125B: Global MASTER-Net observations report
  91. SVOM GRB260121.06: Global MASTER-Net observations report
  92. GRB 260101A: 239Alferov CubeSat detection
  93. Fermi trigger No 790601190: Global MASTER-Net observations report
  94. EP260119a: Global MASTER-Net observations report
  95. GRB 260110A: SVOM detection of a burst through offline search
  96. SVOM GRB260117.82: Global MASTER-Net observations report
  97. Swift triggered on the HMXB 1A 1118-61
  98. GRB 251222A: radio detection with the VLA
  99. Swift GRB 260114A: Global MASTER-Net observations report
  100. Fermi GRB 260105A: Global MASTER-Net observations report

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