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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"

35948 results found.

  1. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  2. GRB 260130A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 260129A: Global MASTER-Net observations report
  4. GRB 260128B: LCO optical upper limits
  5. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  6. IPN triangulation of GRB 260121A
  7. GRB 260127A: Swift-BAT refined analysis
  8. GRB 260129B: Fermi GBM Final Localization
  9. GRB 260128B: SVOM detection of a burst through offline search
  10. GRB 260129A: Fermi GBM Final Localization
  11. IPN triangulation of GRB 260127B (short)
  12. GRB 260127B: Swift-XRT observations
  13. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  14. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  15. Fermi GRB 260127A: Global MASTER-Net observations report
  16. GRB 260127A: Fermi GBM Observation
  17. GRB 260127A: COLIBRÍ optical observations
  18. GRB 260127A: NOT optical observations
  19. GRB 260127B: Swift ToO observations
  20. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  21. GRB 260127A: Swift-XRT refined Analysis
  22. GRB 260127B: GOTO candidate optical counterpart
  23. GRB 260127A: SVOM/C-GFT optical observations
  24. GRB 260127A: Enhanced Swift-XRT position
  25. Fermi GRB 260127B: Global MASTER-Net observations report
  26. GRB 260127B: Fermi GBM Final Real-time Localization
  27. GRB 260127A: Prompt enhanced Swift-XRT position
  28. Swift GRB 260127A: Global MASTER-Net observations report
  29. GRB 260127A: LCO optical afterglow discovery
  30. GRB 260127A: Swift detection of a burst
  31. GRB 260127A: Fermi GBM Final Real-time Localization
  32. GRB 260125A: Swift-XRT observations
  33. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  34. Konus-Wind detection of GRB 260120B
  35. GRB 251222A: SVOM/ECLAIRs refined analysis
  36. GRB 260125A: Swift ToO observations
  37. GRB 260125A: GOTO candidate optical counterpart
  38. Fermi GRB 260125B: Global MASTER-Net observations report
  39. GRB 260125B: Fermi GBM Final Real-time Localization
  40. GRB 260125A: Fermi GBM Final Real-time Localization
  41. GRB 260114A: SVOM/VT optical upper limits
  42. GRB 260120A: AstroSat CZTI detection
  43. GRB 260122B: Swift-BAT refined analysis
  44. GRB 260120B: SVOM/GRM observation
  45. GRB 260120A: GECAM-B observation
  46. GRB 260120B: AstroSat CZTI detection
  47. GRB 260114A: Insight-HXMT/HE detection
  48. GRB 260122B: Swift detection of a burst
  49. EP260119a: Assy AZT-20 optical observations
  50. EP260119a: Mondy and SAO RAS optical upper limits
  51. GRB 260122A: Fermi GBM Final Real-time Localization
  52. Fermi GRB 260120C: Global MASTER-Net observations report
  53. GRB 260120B: Swift-BAT refined analysis
  54. GRB 260120B: Swift-XRT refined Analysis
  55. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  56. GRB 260120B: Fermi GBM Observation
  57. GRB 260120B: Swift/UVOT Detection
  58. GRB 260120B: COLIBRÍ optical upper limits
  59. GRB 260120B: Enhanced Swift-XRT position
  60. GRB 260120B: SVOM/C-GFT optical counterpart detection
  61. GRB 260120C: Fermi GBM Final Real-time Localization
  62. GRB 260101A: 239Alferov CubeSat detection
  63. GRB 260120B: Swift detection of a burst
  64. GRB 260120B: Fermi GBM Final Real-time Localization
  65. EP260119A: Mondy I-Band Observations
  66. GRB 260114A: Swift/UVOT Upper Limits
  67. GRB 251202A: further radio observations with the VLA
  68. EP260119a: KAIT optical observations
  69. GRB 260120A: Fermi GBM Final Real-time Localization
  70. EP260119a: SAO RAS optical observations
  71. GRB 251208D: SVOM/ECLAIRs refined analysis
  72. GRB 251208D: SVOM/ECLAIRs refined analysis
  73. GRB 260117A: Swift-XRT afterglow detection
  74. GRB 260115A: AstroSat CZTI detection
  75. GRB 260117A: ZTSh optical upper limit
  76. GRB 260110A: SVOM detection of a burst through offline search
  77. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. GRB 260117A: SVOM/VT optical candidate
  79. GRB 260117A: SVOM/C-GFT upper limit
  80. GRB 260117A: Swift-XRT observations
  81. GRB 260117A: Swift ToO observations
  82. GRB 260117A: SVOM detection of a long faint burst
  83. GRB 260115A: GECAM-B observation
  84. GRB 260114A: VLT/MUSE spectroscopic observations
  85. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  86. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  87. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  88. Fermi GRB 260115A: Global MASTER-Net observations report
  89. GRB 260115A: Fermi GBM Final Real-time Localization
  90. GRB 251222A: radio detection with the VLA
  91. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  92. Konus-Wind detection of GRB 260114A
  93. GRB 260114A: Swift-XRT refined Analysis
  94. GRB 260114A: 6 GHz VLA observations
  95. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  96. GRB 260114A : MITSuME Akeno optical upper limits
  97. GRB 260114A: COLIBRÍ optical upper limits
  98. GRB 260114A: TNG NIR upper limit
  99. GRB 260114A: NOT optical observations
  100. Konus-Wind detection of GRB 251230A / EP251230a

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