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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"

26507 results found.

  1. GRB 260204A: Swift-XRT observations
  2. GRB 260204A: SVOM/VT optical candidate
  3. GRB 260204A : MASTER Global robotic net optical observations
  4. GRB 260204A: LCO optical upper limits
  5. EP260110a: Late GTC/EMIR near-infrared observations
  6. GRB 260204A: SVOM detection of a burst
  7. GRB 260131A: KAIT optical observations
  8. GRB 251230A: MeerLICHT afterglow detection
  9. GRB 260130A: GECAM-B observation of a short burst
  10. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  11. GRB 260131A/B: EP/FXT X-ray afterglow detection
  12. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  13. EP260131a: Liverpool Telescope optical upper limits
  14. EP260131a: COLIBRÍ further observations
  15. Konus-Wind detection of GRB 260128A / EP260128a
  16. Konus-Wind detection of GRB 260131A/B
  17. EP260131a: SVOM/VT optical observation
  18. EP260131a: Xinglong optical upper limit
  19. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  20. GRB 260131A/B: Fermi GBM Observation
  21. EP260131a: COLIBRÍ observations of slow optical fading
  22. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  24. EP260131a: COLIBRÍ optical observations of the counterpart
  25. GRB 260130A: Fermi GBM Detection
  26. EP260131a: Einstein Probe detection of an X-ray transient
  27. GRB 260127B: Fermi GBM Detection
  28. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  29. GRB 260128B: LCO optical upper limits
  30. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  31. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  32. GRB 260127B: Swift-XRT observations
  33. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  34. EP260128a: NOT optical counterpart candidate
  35. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260128a: Liverpool Telescope optical observations and possible counterpart
  37. EP260128a: LCO optical upper limits
  38. EP260128a: Einstein Probe detection of an X-ray transient
  39. GRB 260127A: Fermi GBM Observation
  40. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 260127A: COLIBRÍ optical observations
  42. EP260126a: Seimei/TriCCS optical upper limit
  43. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  44. GRB 260127A: Swift-XRT refined Analysis
  45. GRB 260127A: SVOM/C-GFT optical observations
  46. The EP-WXT trigger 01709253145 is likely a flaring star
  47. GRB 260127A: Enhanced Swift-XRT position
  48. GRB 260127A: LCO optical afterglow discovery
  49. GRB 260127A: Swift detection of a burst
  50. GRB 260125A: Swift-XRT observations
  51. EP260126a: EP-FXT follow-up observation
  52. EP260126a: Optical upper limit with Kinder observations
  53. EP260126a: Liverpool Telescope optical upper limits
  54. EP260126a: Further NOT optical upper limits
  55. EP260126a: COLIBRÍ optical upper limits
  56. EP260126a: NOT optical observations
  57. EP260126a: Einstein Probe detection of a fast X-ray transient
  58. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  59. Konus-Wind detection of GRB 260120B
  60. GRB 251222A: SVOM/ECLAIRs refined analysis
  61. GRB 260125A: GOTO candidate optical counterpart
  62. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  63. GRB 260114A: SVOM/VT optical upper limits
  64. GRB 260120B: SVOM/GRM observation
  65. EP260119a: Assy AZT-20 optical observations
  66. EP260119a: Mondy and SAO RAS optical upper limits
  67. EP260119a: Xinglong optical upper limit
  68. The EP-WXT trigger 01709251871 is likely a flaring star
  69. GRB 260120B: Swift-XRT refined Analysis
  70. EP260116a: COLIBRÍ further observations
  71. GRB 260120B: Fermi GBM Observation
  72. EP260105a: GTC/HiPERCAM optical observations
  73. GRB 260120B: Swift/UVOT Detection
  74. GRB 260120B: COLIBRÍ optical upper limits
  75. GRB 260120B: Enhanced Swift-XRT position
  76. GRB 260120B: SVOM/C-GFT optical counterpart detection
  77. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  78. GRB 260120B: Swift detection of a burst
  79. EP260119A: Mondy I-Band Observations
  80. GRB 260114A: Swift/UVOT Upper Limits
  81. EP260119a: Liverpool Telescope optical follow-up observations
  82. GRB 251202A: further radio observations with the VLA
  83. EP260119a: KAIT optical observations
  84. EP260119a: SVOM/VT optical observation
  85. EP260119a: update of EP-FXT follow-up observation
  86. EP260119a: NOT optical observations
  87. EP260119a: SAO RAS optical observations
  88. EP260116a: COLIBRÍ detection of a fading optical source
  89. GRB 251208D: SVOM/ECLAIRs refined analysis
  90. GRB 251208D: SVOM/ECLAIRs refined analysis
  91. GRB 260117A: Swift-XRT afterglow detection
  92. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  93. EP260119a: LCO optical observations
  94. GRB 260117A: ZTSh optical upper limit
  95. EP260119a: COLIBRÍ optical counterpart candidate
  96. EP260119a: preliminary result from the EP-FXT observation
  97. GRB 260110A: SVOM detection of a burst through offline search
  98. EP260119a: EP-WXT detection of a fast X-ray transient
  99. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. Fermi-LAT Gamma-ray Observations of IceCube-260115A

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