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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"

28243 results found.

  1. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  2. EP260209a: COLIBRÍ optical upper limit
  3. Fermi GRB 260210C: Global MASTER-Net observations report
  4. EP260209a: LCO optical upper limits
  5. EP260210a: Global MASTER-Net observations report
  6. EP260210a: refined analysis of the EP-FXT observation
  7. EP260209a: Global MASTER-Net observations report
  8. GRB 260208A: LCO detection of the optical counterpart
  9. EP260209a: Einstein Probe detection of a fast X-ray transient
  10. EP260210a: Optical upper limits with Kinder observations
  11. GRB 260210A: Glowbug gamma-ray detection
  12. GRB 260208C: AstroSat CZTI detection
  13. EP260210a: COLIBRÍ optical upper limit
  14. EP260210a: SVOM/C-GFT upper limit
  15. EP260210a: Einstein Probe detection of an X-ray transient
  16. GRB 260207B: AstroSat CZTI detection
  17. GRB 260208C: SVOM/GRM observation
  18. GRB 260204A: Swift-XRT afterglow detection
  19. GRB 260208B: AstroSat CZTI detection of a bright long burst
  20. GRB260208A: Liverpool Telescope optical follow-up observations
  21. GRB 260208A: Glowbug gamma-ray detection
  22. GRB 260208A: NuSTAR detection of prompt emission
  23. GRB 260208A: Fermi GBM Observation
  24. Fermi GRB 260209A: Global MASTER-Net observations report
  25. GRB 260208B: Swift-XRT observations
  26. GRB 260131A/B: continued Mondy optical observations
  27. GRB 260204A: Swift/UVOT Upper Limits
  28. GRB 260208B: COLIBRÍ optical observations
  29. GRB 260208A: Mondy optical observations
  30. GRB 260208A: 1.3m DFOT optical detection
  31. GRB 260208A: COLIBRÍ optical observations
  32. GRB 260208B: EP-FXT observation
  33. Fermi GRB 260208C: Global MASTER-Net observations report
  34. GRB 260208B: SVOM/VT optical candidate
  35. GRB 260208A: GECAM-B observation of a bright burst
  36. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  37. GRB 260208A: SVOM/VT optical observation
  38. Fermi GRB 260208D: Global MASTER-Net observations report
  39. GRB 260208A: Swift-XRT observations
  40. GRB 260208B: SVOM/GRM observation of a bright burst
  41. GRB 260208B: Fermi GBM Detection
  42. LAT GRB 260208B: Global MASTER-Net observations report
  43. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  44. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  45. Fermi GRB 260208A: Global MASTER-Net observations report
  46. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  47. GRB 260131A/B: Mondy and Terskol optical observations
  48. Fermi GRB 260207B: Global MASTER-Net observations report
  49. GRB 260206A: Swift-XRT observations
  50. Fermi trigger No 792135758: Global MASTER-Net observations report
  51. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  52. GRB 260204A: Swift-XRT observations
  53. GRB 260204A: SVOM/VT optical candidate
  54. GRB 260204A : MASTER Global robotic net optical observations
  55. Fermi GBM Sub-Threshold Detection of GRB 260204A
  56. GRB 260204A: LCO optical upper limits
  57. EP260110a: Late GTC/EMIR near-infrared observations
  58. GRB 260121A: 239Alferov CubeSat detection
  59. GRB 260131A: KAIT optical observations
  60. GRB 251230A: MeerLICHT afterglow detection
  61. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  62. GRB 260130A: Insight-HXMT/HE detection
  63. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  64. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  65. GRB 260127A: GECAM-B observation
  66. EP260131a: Liverpool Telescope optical upper limits
  67. EP260131a: COLIBRÍ further observations
  68. EP260131a: SVOM/VT optical observation
  69. EP260131a: Xinglong optical upper limit
  70. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  71. GRB 260131A/B: Fermi GBM Observation
  72. EP260131a: COLIBRÍ observations of slow optical fading
  73. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  74. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  75. GRB 260131B: MAXI/GSC detection
  76. EP260131a: COLIBRÍ optical observations of the counterpart
  77. EP260131a: Las Cumbres detection of an optical counterpart
  78. GRB 260127B: AstroSat CZTI detection
  79. GRB 260130A: Fermi GBM Detection
  80. EP260131a: Einstein Probe detection of an X-ray transient
  81. GRB 260127B: Fermi GBM Detection
  82. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  83. Fermi GRB 260130A: Global MASTER-Net observations report
  84. Fermi GRB 260129A: Global MASTER-Net observations report
  85. GRB 260128B: LCO optical upper limits
  86. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  87. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  88. GRB 260127A: Swift-BAT refined analysis
  89. GRB 260127B: Swift-XRT observations
  90. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  91. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  92. EP260128a: NOT optical counterpart candidate
  93. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  94. EP260128a: Liverpool Telescope optical observations and possible counterpart
  95. EP260128a: LCO optical upper limits
  96. EP260128a: Global MASTER-Net observations report
  97. EP260128a: Einstein Probe detection of an X-ray transient
  98. Fermi GRB 260127A: Global MASTER-Net observations report
  99. GRB 260127A: Fermi GBM Observation
  100. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube

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