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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"

18334 results found.

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

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