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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"
  1. GRB 250204A: SVOM/VT optical candidate
  2. GRB 260204A : MASTER Global robotic net optical observations
  3. Fermi GBM Sub-Threshold Detection of GRB 260204A
  4. GRB 260204A: GOTO optical upper limit
  5. GRB 260204A: LCO optical upper limits
  6. EP260110a: Late GTC/EMIR near-infrared observations
  7. GRB 260204B: Fermi GBM Final Real-time Localization
  8. GRB 260204A: SVOM detection of a burst
  9. GRB 260121A: 239Alferov CubeSat detection
  10. Konus-Wind detection of GRB 260121A
  11. GRB 260131A/B: OHP/T193 optical observations
  12. GRB 260131A: KAIT optical observations
  13. GRB 251230A: MeerLICHT afterglow detection
  14. GRB 260131A: FTW optical and NIR observations
  15. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  16. GRID detection of GRB 260131A/B
  17. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  18. GRB 260130A: Insight-HXMT/HE detection
  19. GRB 260130A: GECAM-B observation of a short burst
  20. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  21. GRB 260131A/B: EP/FXT X-ray afterglow detection
  22. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  23. GRB 260127B: Insight-HXMT/HE detection
  24. GRB 260127B: GECAM-B observation of a short burst
  25. GRB 260127A: GECAM-B observation
  26. GRB 260131A: NOT spectroscopic redshift z = 1.434
  27. EP260131a: Liverpool Telescope optical upper limits
  28. EP260131a: COLIBRÍ further observations
  29. Konus-Wind detection of GRB 260128A / EP260128a
  30. GRB 260131A: Insight-HXMT/HE detection
  31. Konus-Wind detection of GRB 260131A/B
  32. EP260131a: SVOM/VT optical observation
  33. EP260131a: Xinglong optical upper limit
  34. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  35. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  36. GRB 260131A/B: Fermi GBM Observation
  37. EP260131a: COLIBRÍ observations of slow optical fading
  38. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  40. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  41. GRB 260131B: MAXI/GSC detection
  42. GRB 260131A: Fermi GBM Final Real-time Localization
  43. EP260131a: COLIBRÍ optical observations of the counterpart
  44. EP260131a: Las Cumbres detection of an optical counterpart
  45. GRB 260127B: AstroSat CZTI detection
  46. GRB 260130A: Fermi GBM Detection
  47. EP260131a: Einstein Probe detection of an X-ray transient
  48. GRB 260127B: Fermi GBM Detection
  49. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  50. Fermi GRB 260130A: Global MASTER-Net observations report
  51. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  52. GRB 260130A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260129A: Global MASTER-Net observations report
  54. GRB 260128B: LCO optical upper limits
  55. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  56. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  57. IPN triangulation of GRB 260121A
  58. GRB 260127A: Swift-BAT refined analysis
  59. GRB 260129B: Fermi GBM Final Localization
  60. GRB 260128B: SVOM detection of a burst through offline search
  61. GRB 260129A: Fermi GBM Final Localization
  62. IPN triangulation of GRB 260127B (short)
  63. GRB 260127B: Swift-XRT observations
  64. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  65. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  66. EP260128a: NOT optical counterpart candidate
  67. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  68. EP260128a: Liverpool Telescope optical observations and possible counterpart
  69. EP260128a: LCO optical upper limits
  70. EP260126a: SVOM/VT optical upperlimit
  71. EP260128a: Global MASTER-Net observations report
  72. EP260128a: Einstein Probe detection of an X-ray transient
  73. Fermi GRB 260127A: Global MASTER-Net observations report
  74. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  75. GRB 260127A: Fermi GBM Observation
  76. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 260127A: COLIBRÍ optical observations
  78. GRB 260127A: NOT optical observations
  79. GRB 260127B: Swift ToO observations
  80. EP260126a: Seimei/TriCCS optical upper limit
  81. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  82. GRB 260127A: Swift-XRT refined Analysis
  83. GRB 260127B: GOTO candidate optical counterpart
  84. GRB 260127A: SVOM/C-GFT optical observations
  85. The EP-WXT trigger 01709253145 is likely a flaring star
  86. GRB 260127A: Enhanced Swift-XRT position
  87. Fermi GRB 260127B: Global MASTER-Net observations report
  88. GRB 260127B: Fermi GBM Final Real-time Localization
  89. GRB 260127A: Prompt enhanced Swift-XRT position
  90. Swift GRB 260127A: Global MASTER-Net observations report
  91. GRB 260127A: LCO optical afterglow discovery
  92. GRB 260127A: Swift detection of a burst
  93. GRB 260127A: Fermi GBM Final Real-time Localization
  94. GRB 260125A: Swift-XRT observations
  95. EP260126a: EP-FXT follow-up observation
  96. EP260126a: Optical upper limit with Kinder observations
  97. EP260126a: Liverpool Telescope optical upper limits
  98. EP260126a: Further NOT optical upper limits
  99. EP260126a: COLIBRÍ optical upper limits
  100. EP260126a: NOT optical observations

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