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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"

32501 results found.

  1. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  2. EP260128a: Liverpool Telescope optical observations and possible counterpart
  3. EP260128a: LCO optical upper limits
  4. EP260126a: SVOM/VT optical upperlimit
  5. EP260128a: Global MASTER-Net observations report
  6. Fermi GRB 260127A: Global MASTER-Net observations report
  7. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  8. GRB 260127A: Fermi GBM Observation
  9. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 260127A: COLIBRÍ optical observations
  11. GRB 260127A: NOT optical observations
  12. GRB 260127B: Swift ToO observations
  13. EP260126a: Seimei/TriCCS optical upper limit
  14. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  15. GRB 260127B: GOTO candidate optical counterpart
  16. GRB 260127A: SVOM/C-GFT optical observations
  17. Fermi GRB 260127B: Global MASTER-Net observations report
  18. Swift GRB 260127A: Global MASTER-Net observations report
  19. GRB 260127A: LCO optical afterglow discovery
  20. GRB 260125A: Swift-XRT observations
  21. EP260126a: EP-FXT follow-up observation
  22. EP260126a: Optical upper limit with Kinder observations
  23. EP260126a: Liverpool Telescope optical upper limits
  24. EP260126a: Further NOT optical upper limits
  25. EP260126a: COLIBRÍ optical upper limits
  26. EP260126a: NOT optical observations
  27. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  28. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  29. Konus-Wind detection of GRB 260120B
  30. GRB 251222A: SVOM/ECLAIRs refined analysis
  31. GRB 260125A: Swift ToO observations
  32. GRB 260125A: GOTO candidate optical counterpart
  33. Fermi GRB 260125B: Global MASTER-Net observations report
  34. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  35. GRB 260114A: SVOM/VT optical upper limits
  36. GRB 260120A: AstroSat CZTI detection
  37. GRB 260122B: Swift-BAT refined analysis
  38. GRB 260120B: SVOM/GRM observation
  39. GRB 260120A: GECAM-B observation
  40. GRB 260120B: AstroSat CZTI detection
  41. GRB 260114A: Insight-HXMT/HE detection
  42. EP260119a: Assy AZT-20 optical observations
  43. EP260119a: Mondy and SAO RAS optical upper limits
  44. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  45. EP260119a: Xinglong optical upper limit
  46. Fermi GRB 260120C: Global MASTER-Net observations report
  47. GRB 260120B: Swift-BAT refined analysis
  48. EP260116a: COLIBRÍ further observations
  49. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  50. GRB 260120B: Fermi GBM Observation
  51. EP260105a: GTC/HiPERCAM optical observations
  52. GRB 260120B: Swift/UVOT Detection
  53. GRB 260120B: COLIBRÍ optical upper limits
  54. GRB 260120B: SVOM/C-GFT optical counterpart detection
  55. GRB 260101A: 239Alferov CubeSat detection
  56. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  57. EP260119A: Mondy I-Band Observations
  58. GRB 260114A: Swift/UVOT Upper Limits
  59. EP260119a: Liverpool Telescope optical follow-up observations
  60. GRB 251202A: further radio observations with the VLA
  61. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  62. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  63. EP260119a: KAIT optical observations
  64. EP260119a: SVOM/VT optical observation
  65. EP260119a: update of EP-FXT follow-up observation
  66. EP260119a: NOT optical observations
  67. EP260119a: SAO RAS optical observations
  68. EP260116a: COLIBRÍ detection of a fading optical source
  69. GRB 251208D: SVOM/ECLAIRs refined analysis
  70. GRB 251208D: SVOM/ECLAIRs refined analysis
  71. GRB 260117A: Swift-XRT afterglow detection
  72. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  73. EP260119a: Global MASTER-Net observations report
  74. GRB 260115A: AstroSat CZTI detection
  75. EP260119a: LCO optical observations
  76. GRB 260117A: ZTSh optical upper limit
  77. EP260119a: COLIBRÍ optical counterpart candidate
  78. EP260119a: preliminary result from the EP-FXT observation
  79. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  81. Swift trigger on the HMXB 1A 1118-61
  82. GRB 260117A: SVOM/VT optical candidate
  83. GRB 260117A: SVOM/C-GFT upper limit
  84. GRB 260117A: Swift ToO observations
  85. EP 260116a: COLIBRÍ optical upper limit
  86. GRB 260115A: GECAM-B observation
  87. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  88. EP260116a: Liverpool Telescope upper limits
  89. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  90. EP260116A: 1.3m DFOT optical upper limit
  91. GRB 260114A: VLT/MUSE spectroscopic observations
  92. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  93. EP260116a: Global MASTER-Net observations report
  94. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  95. EP260116a: Xinglong optical upper limit
  96. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  97. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  98. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  99. Fermi GRB 260115A: Global MASTER-Net observations report
  100. GRB260114A: STEP/T80S optical limits

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