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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"

19810 results found.

  1. EP260131a: COLIBRÍ further observations
  2. Konus-Wind detection of GRB 260128A / EP260128a
  3. EP260131a: SVOM/VT optical observation
  4. EP260131a: Xinglong optical upper limit
  5. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  6. EP260131a: COLIBRÍ observations of slow optical fading
  7. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  8. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  9. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  10. EP260131a: COLIBRÍ optical observations of the counterpart
  11. EP260131a: Einstein Probe detection of an X-ray transient
  12. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  13. GRB 260128B: LCO optical upper limits
  14. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  15. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  16. GRB 260128B: SVOM detection of a burst through offline search
  17. GRB 260127B: Swift-XRT observations
  18. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  19. EP260128a: NOT optical counterpart candidate
  20. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  21. EP260128a: Liverpool Telescope optical observations and possible counterpart
  22. EP260128a: LCO optical upper limits
  23. EP260128a: Einstein Probe detection of an X-ray transient
  24. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  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: SVOM/C-GFT optical observations
  29. GRB 260127A: Enhanced Swift-XRT position
  30. GRB 260127A: LCO optical afterglow discovery
  31. GRB 260127A: Swift detection of a burst
  32. GRB 260125A: Swift-XRT observations
  33. EP260126a: Optical upper limit with Kinder observations
  34. EP260126a: Liverpool Telescope optical upper limits
  35. EP260126a: Further NOT optical upper limits
  36. EP260126a: COLIBRÍ optical upper limits
  37. EP260126a: NOT optical observations
  38. EP260126a: Einstein Probe detection of a fast X-ray transient
  39. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  40. GRB 251222A: SVOM/ECLAIRs refined analysis
  41. GRB 260125A: GOTO candidate optical counterpart
  42. GRB 260114A: SVOM/VT optical upper limits
  43. GRB 260120B: SVOM/GRM observation
  44. GRB 260120B: AstroSat CZTI detection
  45. EP260119a: Assy AZT-20 optical observations
  46. EP260119a: Mondy and SAO RAS optical upper limits
  47. EP260119a: Xinglong optical upper limit
  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: Enhanced Swift-XRT position
  55. GRB 260120B: SVOM/C-GFT optical counterpart detection
  56. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  57. GRB 260120B: Swift detection of a burst
  58. EP260119A: Mondy I-Band Observations
  59. GRB 260114A: Swift/UVOT Upper Limits
  60. EP260119a: Liverpool Telescope optical follow-up observations
  61. GRB 251202A: further radio observations with the VLA
  62. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  63. EP260119a: KAIT optical observations
  64. EP260119a: SVOM/VT optical observation
  65. EP260119a: NOT optical observations
  66. EP260119a: SAO RAS optical observations
  67. EP260116a: COLIBRÍ detection of a fading optical source
  68. GRB 251208D: SVOM/ECLAIRs refined analysis
  69. GRB 251208D: SVOM/ECLAIRs refined analysis
  70. GRB 260117A: Swift-XRT afterglow detection
  71. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  72. EP260119a: LCO optical observations
  73. GRB 260117A: ZTSh optical upper limit
  74. EP260119a: COLIBRÍ optical counterpart candidate
  75. GRB 260110A: SVOM detection of a burst through offline search
  76. EP260119a: EP-WXT detection of a fast X-ray transient
  77. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  79. Swift trigger on the HMXB 1A 1118-61
  80. GRB 260117A: SVOM/C-GFT upper limit
  81. GRB 260117A: SVOM detection of a long faint burst
  82. EP 260116a: COLIBRÍ optical upper limit
  83. Swift triggered on the HMXB 1A 1118-61
  84. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  85. EP260116a: Liverpool Telescope upper limits
  86. EP260116A: 1.3m DFOT optical upper limit
  87. GRB 260114A: VLT/MUSE spectroscopic observations
  88. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  90. EP260116a: Xinglong optical upper limit
  91. EP260116a: Einstein Probe detection of an X-ray transient
  92. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  93. GRB 251222A: radio detection with the VLA
  94. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  95. GRB 260114A: Swift-XRT refined Analysis
  96. GRB 260114A: 6 GHz VLA observations
  97. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  98. GRB 260114A : MITSuME Akeno optical upper limits
  99. GRB 260114A: COLIBRÍ optical upper limits
  100. GRB 260114A: TNG NIR upper limit

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