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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"

26922 results found.

  1. EP260126a: Einstein Probe detection of a fast X-ray transient
  2. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  3. Konus-Wind detection of GRB 260120B
  4. GRB 251222A: SVOM/ECLAIRs refined analysis
  5. GRB 260125A: GOTO candidate optical counterpart
  6. Fermi GRB 260125B: Global MASTER-Net observations report
  7. GRB 260125B: Fermi GBM Final Real-time Localization
  8. GRB 260125A: Fermi GBM Final Real-time Localization
  9. GRB 260114A: SVOM/VT optical upper limits
  10. GRB 260122B: Swift-BAT refined analysis
  11. GRB 260120B: SVOM/GRM observation
  12. GRB 260120A: GECAM-B observation
  13. GRB 260122B: Swift detection of a burst
  14. Swift GRB260122.97: Global MASTER-Net observations report
  15. GRB 260122A: Fermi GBM Final Real-time Localization
  16. EP260119a: Xinglong optical upper limit
  17. The EP-WXT trigger 01709251871 is likely a flaring star
  18. Fermi GRB 260120C: Global MASTER-Net observations report
  19. GRB 260120B: Swift-BAT refined analysis
  20. GRB 260120B: Swift-XRT refined Analysis
  21. EP260116a: COLIBRÍ further observations
  22. GRB 260120B: Fermi GBM Observation
  23. EP260105a: GTC/HiPERCAM optical observations
  24. GRB 260120B: Swift/UVOT Detection
  25. GRB 260120B: COLIBRÍ optical upper limits
  26. SVOM GRB260121.06: Global MASTER-Net observations report
  27. GRB 260120B: SVOM/C-GFT optical counterpart detection
  28. GRB 260120C: Fermi GBM Final Real-time Localization
  29. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  30. GRB 260120B: Swift detection of a burst
  31. Swift GRB260120B: Global MASTER-Net observations report
  32. GRB 260120B: Fermi GBM Final Real-time Localization
  33. Fermi trigger No 790601190: Global MASTER-Net observations report
  34. Fermi trigger No 790570272: Global MASTER-Net observations report
  35. GRB 260114A: Swift/UVOT Upper Limits
  36. EP260119a: Liverpool Telescope optical follow-up observations
  37. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  38. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  39. GRB 260120A: Fermi GBM Final Real-time Localization
  40. EP260119a: SVOM/VT optical observation
  41. EP260119a: update of EP-FXT follow-up observation
  42. EP260119a: NOT optical observations
  43. SVOM GRB260119.92: Global MASTER-Net observations report
  44. SVOM GRB260119.92: Global MASTER-Net observations report
  45. SVOM GRB260119.90: Global MASTER-Net observations report
  46. EP260116a: COLIBRÍ detection of a fading optical source
  47. GRB 251208D: SVOM/ECLAIRs refined analysis
  48. GRB 251208D: SVOM/ECLAIRs refined analysis
  49. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  50. EP260119a: Global MASTER-Net observations report
  51. EP260119a: LCO optical observations
  52. EP260119a: COLIBRÍ optical counterpart candidate
  53. EP260119a: preliminary result from the EP-FXT observation
  54. GRB 260110A: SVOM detection of a burst through offline search
  55. EP260119a: EP-WXT detection of a fast X-ray transient
  56. Swift GRB260118.48: Global MASTER-Net observations report
  57. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. SVOM GRB260117.82: Global MASTER-Net observations report
  59. Swift trigger on the HMXB 1A 1118-61
  60. GRB 260117A: SVOM/VT optical candidate
  61. GRB 260117A: SVOM/C-GFT upper limit
  62. GRB 260117A: SVOM detection of a long faint burst
  63. EP 260116a: COLIBRÍ optical upper limit
  64. Swift triggered on the HMXB 1A 1118-61
  65. GRB 260115A: GECAM-B observation
  66. EP260116a: Liverpool Telescope upper limits
  67. EP260116A: 1.3m DFOT optical upper limit
  68. GRB 260114A: VLT/MUSE spectroscopic observations
  69. EP260116a: Global MASTER-Net observations report
  70. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  71. EP260116a: Xinglong optical upper limit
  72. EP260116a: Einstein Probe detection of an X-ray transient
  73. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  74. IceCube Alert 260115.73: Global MASTER-Net observations report
  75. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  76. Fermi GRB 260115A: Global MASTER-Net observations report
  77. GRB 260115A: Fermi GBM Final Real-time Localization
  78. GRB260114A: STEP/T80S optical limits
  79. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  80. GRB 260114A: Swift-XRT refined Analysis
  81. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  82. GRB 260114A : MITSuME Akeno optical upper limits
  83. GRB 260114A: COLIBRÍ optical upper limits
  84. GRB 260114A: NOT optical observations
  85. GRB 260114A: SVOM/GRM observation of a short burst
  86. Swift GRB 260114A: Global MASTER-Net observations report
  87. GRB 260114A: GECAM-B observation of a short burst
  88. GRB 260114A: Fermi GBM observation
  89. GRB 260112B: GECAM-B observation
  90. GRB 260114A: GMG Optical Observation
  91. GRB 260114A: Swift detection of a short burst
  92. GRB 260114A: Fermi GBM Final Real-time Localization
  93. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  94. Swift GRB260113.43: Global MASTER-Net observations report
  95. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  96. EP260110a: TRT optical upper limits
  97. Konus-Wind detection of GRB 260101A
  98. Swift Trigger 1439093: is probably not GRB 260113A
  99. GRB 260111A: COLIBRÍ optical afterglow candidate
  100. GRB 260111A: GECAM-B observation of a burst

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