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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"

42471 results found.

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

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