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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"

17341 results found.

  1. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  2. GRB 260131A/B: Mondy and Terskol optical observations
  3. GRB 260204A: SVOM/VT optical candidate
  4. GRB 260204A: LCO optical upper limits
  5. EP260110a: Late GTC/EMIR near-infrared observations
  6. GRB 260131A: KAIT optical observations
  7. GRB 251230A: MeerLICHT afterglow detection
  8. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  9. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  10. EP260131a: Liverpool Telescope optical upper limits
  11. EP260131a: COLIBRÍ further observations
  12. EP260131a: SVOM/VT optical observation
  13. EP260131a: Xinglong optical upper limit
  14. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  15. EP260131a: COLIBRÍ observations of slow optical fading
  16. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  18. EP260131a: COLIBRÍ optical observations of the counterpart
  19. GRB 260127B: AstroSat CZTI detection
  20. EP260131a: Einstein Probe detection of an X-ray transient
  21. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  22. GRB 260128B: LCO optical upper limits
  23. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  24. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  25. GRB 260127B: Swift-XRT observations
  26. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  27. EP260128a: NOT optical counterpart candidate
  28. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  29. EP260128a: Liverpool Telescope optical observations and possible counterpart
  30. EP260128a: LCO optical upper limits
  31. EP260128a: Einstein Probe detection of an X-ray transient
  32. GRB 260127A: COLIBRÍ optical observations
  33. EP260126a: Seimei/TriCCS optical upper limit
  34. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  35. GRB 260127A: Swift-XRT refined Analysis
  36. GRB 260127B: GOTO candidate optical counterpart
  37. GRB 260127A: SVOM/C-GFT optical observations
  38. The EP-WXT trigger 01709253145 is likely a flaring star
  39. GRB 260127A: Enhanced Swift-XRT position
  40. GRB 260127A: LCO optical afterglow discovery
  41. GRB 260127A: Swift detection of a burst
  42. GRB 260125A: Swift-XRT observations
  43. EP260126a: EP-FXT follow-up observation
  44. EP260126a: Optical upper limit with Kinder observations
  45. EP260126a: Liverpool Telescope optical upper limits
  46. EP260126a: Further NOT optical upper limits
  47. EP260126a: COLIBRÍ optical upper limits
  48. EP260126a: NOT optical observations
  49. EP260126a: Einstein Probe detection of a fast X-ray transient
  50. GRB 251222A: SVOM/ECLAIRs refined analysis
  51. GRB 260125A: GOTO candidate optical counterpart
  52. GRB 260114A: SVOM/VT optical upper limits
  53. GRB 260122B: Swift-BAT refined analysis
  54. GRB 260120B: SVOM/GRM observation
  55. GRB 260120B: AstroSat CZTI detection
  56. EP260119a: Assy AZT-20 optical observations
  57. EP260119a: Mondy and SAO RAS optical upper limits
  58. EP260119a: Xinglong optical upper limit
  59. The EP-WXT trigger 01709251871 is likely a flaring star
  60. GRB 260120B: Swift-BAT refined analysis
  61. GRB 260120B: Swift-XRT refined Analysis
  62. EP260116a: COLIBRÍ further observations
  63. EP260105a: GTC/HiPERCAM optical observations
  64. GRB 260120B: Swift/UVOT Detection
  65. GRB 260120B: COLIBRÍ optical upper limits
  66. GRB 260120B: Enhanced Swift-XRT position
  67. GRB 260120B: SVOM/C-GFT optical counterpart detection
  68. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  69. GRB 260120B: Swift detection of a burst
  70. EP260119A: Mondy I-Band Observations
  71. GRB 260114A: Swift/UVOT Upper Limits
  72. EP260119a: Liverpool Telescope optical follow-up observations
  73. GRB 251202A: further radio observations with the VLA
  74. EP260119a: KAIT optical observations
  75. EP260119a: SVOM/VT optical observation
  76. EP260119a: update of EP-FXT follow-up observation
  77. EP260119a: NOT optical observations
  78. EP260119a: SAO RAS optical observations
  79. EP260116a: COLIBRÍ detection of a fading optical source
  80. GRB 260117A: Swift-XRT afterglow detection
  81. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  82. GRB 260115A: AstroSat CZTI detection
  83. EP260119a: LCO optical observations
  84. GRB 260117A: ZTSh optical upper limit
  85. EP260119a: COLIBRÍ optical counterpart candidate
  86. EP260119a: preliminary result from the EP-FXT observation
  87. EP260119a: EP-WXT detection of a fast X-ray transient
  88. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  89. Swift trigger on the HMXB 1A 1118-61
  90. GRB 260117A: SVOM/C-GFT upper limit
  91. EP 260116a: COLIBRÍ optical upper limit
  92. Swift triggered on the HMXB 1A 1118-61
  93. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  94. EP260116a: Liverpool Telescope upper limits
  95. EP260116A: 1.3m DFOT optical upper limit
  96. GRB 260114A: VLT/MUSE spectroscopic observations
  97. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  98. EP260116a: Xinglong optical upper limit
  99. EP260116a: Einstein Probe detection of an X-ray transient
  100. GRB 260114A: VLT/HAWK-I further near-infrared upper limits

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