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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"

20964 results found.

  1. GRB 260125A: Swift ToO observations
  2. GRB 260125A: GOTO candidate optical counterpart
  3. Fermi GRB 260125B: Global MASTER-Net observations report
  4. Swift GRB260122.97: Global MASTER-Net observations report
  5. EP260119a: Assy AZT-20 optical observations
  6. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  7. Fermi GRB 260120C: Global MASTER-Net observations report
  8. EP260116a: COLIBRÍ further observations
  9. EP260105a: GTC/HiPERCAM optical observations
  10. GRB 260120B: Swift/UVOT Detection
  11. SVOM GRB260121.06: Global MASTER-Net observations report
  12. GRB 260101A: 239Alferov CubeSat detection
  13. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  14. Swift GRB260120B: Global MASTER-Net observations report
  15. EP260119A: Mondy I-Band Observations
  16. Fermi trigger No 790601190: Global MASTER-Net observations report
  17. Fermi trigger No 790570272: Global MASTER-Net observations report
  18. GRB 260114A: Swift/UVOT Upper Limits
  19. EP260119a: Liverpool Telescope optical follow-up observations
  20. GRB 251202A: further radio observations with the VLA
  21. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  22. EP260119a: KAIT optical observations
  23. EP260119a: update of EP-FXT follow-up observation
  24. EP260119a: NOT optical observations
  25. EP260119a: SAO RAS optical observations
  26. SVOM GRB260119.92: Global MASTER-Net observations report
  27. SVOM GRB260119.92: Global MASTER-Net observations report
  28. SVOM GRB260119.90: Global MASTER-Net observations report
  29. EP260116a: COLIBRÍ detection of a fading optical source
  30. GRB 251208D: SVOM/ECLAIRs refined analysis
  31. GRB 251208D: SVOM/ECLAIRs refined analysis
  32. GRB 260117A: Swift-XRT afterglow detection
  33. EP260119a: Global MASTER-Net observations report
  34. EP260119a: LCO optical observations
  35. EP260119a: COLIBRÍ optical counterpart candidate
  36. Swift GRB260118.48: Global MASTER-Net observations report
  37. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  38. SVOM GRB260117.82: Global MASTER-Net observations report
  39. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  40. Swift trigger on the HMXB 1A 1118-61
  41. GRB 260117A: SVOM/C-GFT upper limit
  42. GRB 260117A: Swift-XRT observations
  43. GRB 260117A: Swift ToO observations
  44. Swift triggered on the HMXB 1A 1118-61
  45. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  46. EP260116A: 1.3m DFOT optical upper limit
  47. GRB 260114A: VLT/MUSE spectroscopic observations
  48. EP260116a: Global MASTER-Net observations report
  49. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  50. IceCube Alert 260115.73: Global MASTER-Net observations report
  51. Fermi GRB 260115A: Global MASTER-Net observations report
  52. GRB260114A: STEP/T80S optical limits
  53. GRB 251222A: radio detection with the VLA
  54. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  55. GRB 260114A: 6 GHz VLA observations
  56. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  57. GRB 260114A: NOT optical observations
  58. Swift GRB 260114A: Global MASTER-Net observations report
  59. GRB 260114A: Mondy optical observations
  60. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  61. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  62. Swift GRB260113.43: Global MASTER-Net observations report
  63. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  64. EP260110a: TRT optical upper limits
  65. GRB 260111A: Swift-XRT observations
  66. GRB 260111A: GOTO optical upper limits
  67. GRB 260111A: Swift ToO observations
  68. GRB 251230A: Mondy Optical Observations
  69. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  70. IceCube Alert 260111A: Global MASTER-Net observations report
  71. EP260110a: Global MASTER-Net observations report
  72. Fermi GRB 260111A: Global MASTER-Net observations report
  73. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP 260110a: COLIBRÍ optical observations
  75. EP260110a: SVOM/C-GFT upper limit
  76. GRB 260109C: LCO optical upper limits
  77. GRB 260109C: Kilonova-Catcher optical upper limit
  78. GRB 260102A: Swift-XRT afterglow detection
  79. Fermi GRB 260107A: Global MASTER-Net observations report
  80. GRB 260102A: AbAO optical observations
  81. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  82. Fermi GRB 260105A: Global MASTER-Net observations report
  83. EP260105a: FTW optical observations
  84. EP260104a: FTW optical observations
  85. Fermi GRB 260105B: Global MASTER-Net observations report
  86. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  87. EP260105a: LCO Optical Upper limit
  88. EP260104a: Global MASTER-Net observations report
  89. EP260104a: Einstein Probe detection of a fast X-ray transient
  90. EP260105a: Global MASTER-Net observations report
  91. Fermi GRB 260104B: Global MASTER-Net observations report
  92. Swift GRB 260104A: Global MASTER-Net observations report
  93. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  94. GRB 260101A: Swift/UVOT Detection
  95. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  96. GRB 260101A: COLIBRÍ optical observations
  97. SVOM GRB260103.08: Global MASTER-Net observations report
  98. SVOM GRB260102A: Global MASTER-Net observations report
  99. EP260101a: Global MASTER-Net observations report
  100. GRB 260102A: Swift-XRT observations

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