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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"

43583 results found.

  1. Fermi GRB 260207B: Global MASTER-Net observations report
  2. GRB 260206A: Swift-XRT observations
  3. GRB 260207B: Fermi GBM Final Real-time Localization
  4. GRB 260207A: Fermi GBM Final Localization
  5. Fermi trigger No 792135758: Global MASTER-Net observations report
  6. EP260131a: VLA detection
  7. GRB 260206A: Tiled Swift observations
  8. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  9. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  10. GRB 260204A: Swift-XRT observations
  11. GRB 260204A: LCO optical afterglow detection
  12. GRB 260204A: SVOM/VT optical candidate
  13. GRB 260204A : MASTER Global robotic net optical observations
  14. Fermi GBM Sub-Threshold Detection of GRB 260204A
  15. GRB 260204A: GOTO optical upper limit
  16. GRB 260204A: LCO optical upper limits
  17. EP260110a: Late GTC/EMIR near-infrared observations
  18. GRB 260204B: Fermi GBM Final Real-time Localization
  19. GRB 260204A: SVOM detection of a burst
  20. GRB 260121A: 239Alferov CubeSat detection
  21. Konus-Wind detection of GRB 260121A
  22. GRB 260131A/B: OHP/T193 optical observations
  23. GRB 260131A: KAIT optical observations
  24. GRB 251230A: MeerLICHT afterglow detection
  25. GRB 260131A: FTW optical and NIR observations
  26. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  27. GRID detection of GRB 260131A/B
  28. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  29. GRB 260130A: Insight-HXMT/HE detection
  30. GRB 260130A: GECAM-B observation of a short burst
  31. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  32. GRB 260131A/B: EP/FXT X-ray afterglow detection
  33. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  34. GRB 260127B: Insight-HXMT/HE detection
  35. GRB 260127B: GECAM-B observation of a short burst
  36. GRB 260127A: GECAM-B observation
  37. GRB 260131A: NOT spectroscopic redshift z = 1.434
  38. EP260131a: Liverpool Telescope optical upper limits
  39. EP260131a: COLIBRÍ further observations
  40. Konus-Wind detection of GRB 260128A / EP260128a
  41. GRB 260131A: Insight-HXMT/HE detection
  42. Konus-Wind detection of GRB 260131A/B
  43. EP260131a: SVOM/VT optical observation
  44. EP260131a: Xinglong optical upper limit
  45. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  46. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  47. GRB 260131A/B: Fermi GBM Observation
  48. EP260131a: COLIBRÍ observations of slow optical fading
  49. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  50. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  51. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  52. GRB 260131B: MAXI/GSC detection
  53. GRB 260131A: Fermi GBM Final Real-time Localization
  54. EP260131a: COLIBRÍ optical observations of the counterpart
  55. EP260131a: Las Cumbres detection of an optical counterpart
  56. GRB 260127B: AstroSat CZTI detection
  57. GRB 260130A: Fermi GBM Detection
  58. EP260131a: Einstein Probe detection of an X-ray transient
  59. GRB 260127B: Fermi GBM Detection
  60. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  61. Fermi GRB 260130A: Global MASTER-Net observations report
  62. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  63. GRB 260130A: Fermi GBM Final Real-time Localization
  64. Fermi GRB 260129A: Global MASTER-Net observations report
  65. GRB 260128B: LCO optical upper limits
  66. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  67. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  68. IPN triangulation of GRB 260121A
  69. GRB 260127A: Swift-BAT refined analysis
  70. GRB 260129B: Fermi GBM Final Localization
  71. GRB 260128B: SVOM detection of a burst through offline search
  72. GRB 260129A: Fermi GBM Final Localization
  73. IPN triangulation of GRB 260127B (short)
  74. GRB 260127B: Swift-XRT observations
  75. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  76. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  77. EP260128a: NOT optical counterpart candidate
  78. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  79. EP260128a: Liverpool Telescope optical observations and possible counterpart
  80. EP260128a: LCO optical upper limits
  81. EP260126a: SVOM/VT optical upperlimit
  82. EP260128a: Global MASTER-Net observations report
  83. EP260128a: Einstein Probe detection of an X-ray transient
  84. Fermi GRB 260127A: Global MASTER-Net observations report
  85. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  86. GRB 260127A: Fermi GBM Observation
  87. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 260127A: COLIBRÍ optical observations
  89. GRB 260127A: NOT optical observations
  90. GRB 260127B: Swift ToO observations
  91. EP260126a: Seimei/TriCCS optical upper limit
  92. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  93. GRB 260127A: Swift-XRT refined Analysis
  94. GRB 260127B: GOTO candidate optical counterpart
  95. GRB 260127A: SVOM/C-GFT optical observations
  96. The EP-WXT trigger 01709253145 is likely a flaring star
  97. GRB 260127A: Enhanced Swift-XRT position
  98. Fermi GRB 260127B: Global MASTER-Net observations report
  99. GRB 260127B: Fermi GBM Final Real-time Localization
  100. GRB 260127A: Prompt enhanced Swift-XRT position

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