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

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