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

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