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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"

26949 results found.

  1. EP260128a: Liverpool Telescope optical observations and possible counterpart
  2. EP260128a: LCO optical upper limits
  3. EP260128a: Global MASTER-Net observations report
  4. EP260128a: Einstein Probe detection of an X-ray transient
  5. Fermi GRB 260127A: Global MASTER-Net observations report
  6. GRB 260127A: Fermi GBM Observation
  7. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 260127A: COLIBRÍ optical observations
  9. EP260126a: Seimei/TriCCS optical upper limit
  10. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  11. GRB 260127A: Swift-XRT refined Analysis
  12. GRB 260127A: SVOM/C-GFT optical observations
  13. GRB 260127A: Enhanced Swift-XRT position
  14. Fermi GRB 260127B: Global MASTER-Net observations report
  15. Swift GRB 260127A: Global MASTER-Net observations report
  16. GRB 260127A: LCO optical afterglow discovery
  17. GRB 260127A: Swift detection of a burst
  18. GRB 260125A: Swift-XRT observations
  19. EP260126a: Optical upper limit with Kinder observations
  20. EP260126a: Liverpool Telescope optical upper limits
  21. EP260126a: Further NOT optical upper limits
  22. EP260126a: COLIBRÍ optical upper limits
  23. EP260126a: NOT optical observations
  24. EP260126a: Einstein Probe detection of a fast X-ray transient
  25. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  26. GRB 251222A: SVOM/ECLAIRs refined analysis
  27. GRB 260125A: GOTO candidate optical counterpart
  28. Fermi GRB 260125B: Global MASTER-Net observations report
  29. GRB 260114A: SVOM/VT optical upper limits
  30. GRB 260122B: Swift-BAT refined analysis
  31. GRB 260120B: SVOM/GRM observation
  32. Swift GRB260122.97: Global MASTER-Net observations report
  33. EP260119a: Assy AZT-20 optical observations
  34. EP260119a: Mondy and SAO RAS optical upper limits
  35. EP260119a: Xinglong optical upper limit
  36. Fermi GRB 260120C: Global MASTER-Net observations report
  37. GRB 260120B: Swift-BAT refined analysis
  38. GRB 260120B: Swift-XRT refined Analysis
  39. EP260116a: COLIBRÍ further observations
  40. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  41. GRB 260120B: Fermi GBM Observation
  42. EP260105a: GTC/HiPERCAM optical observations
  43. GRB 260120B: Swift/UVOT Detection
  44. GRB 260120B: COLIBRÍ optical upper limits
  45. SVOM GRB260121.06: Global MASTER-Net observations report
  46. GRB 260120B: Enhanced Swift-XRT position
  47. GRB 260120B: SVOM/C-GFT optical counterpart detection
  48. GRB 260101A: 239Alferov CubeSat detection
  49. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  50. GRB 260120B: Swift detection of a burst
  51. Swift GRB260120B: Global MASTER-Net observations report
  52. EP260119A: Mondy I-Band Observations
  53. Fermi trigger No 790601190: Global MASTER-Net observations report
  54. Fermi trigger No 790570272: Global MASTER-Net observations report
  55. GRB 260114A: Swift/UVOT Upper Limits
  56. EP260119a: Liverpool Telescope optical follow-up observations
  57. GRB 251202A: further radio observations with the VLA
  58. EP260119a: KAIT optical observations
  59. EP260119a: SVOM/VT optical observation
  60. EP260119a: NOT optical observations
  61. EP260119a: SAO RAS optical observations
  62. SVOM GRB260119.92: Global MASTER-Net observations report
  63. SVOM GRB260119.92: Global MASTER-Net observations report
  64. SVOM GRB260119.90: Global MASTER-Net observations report
  65. EP260116a: COLIBRÍ detection of a fading optical source
  66. GRB 260117A: Swift-XRT afterglow detection
  67. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  68. EP260119a: Global MASTER-Net observations report
  69. EP260119a: LCO optical observations
  70. GRB 260117A: ZTSh optical upper limit
  71. EP260119a: COLIBRÍ optical counterpart candidate
  72. EP260119a: EP-WXT detection of a fast X-ray transient
  73. Swift GRB260118.48: Global MASTER-Net observations report
  74. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. SVOM GRB260117.82: Global MASTER-Net observations report
  76. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  77. Swift trigger on the HMXB 1A 1118-61
  78. GRB 260117A: SVOM/VT optical candidate
  79. GRB 260117A: SVOM/C-GFT upper limit
  80. GRB 260117A: Swift-XRT observations
  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. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  87. EP260116A: 1.3m DFOT optical upper limit
  88. GRB 260114A: VLT/MUSE spectroscopic observations
  89. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  90. EP260116a: Global MASTER-Net observations report
  91. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  92. EP260116a: Xinglong optical upper limit
  93. EP260116a: Einstein Probe detection of an X-ray transient
  94. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  95. IceCube Alert 260115.73: Global MASTER-Net observations report
  96. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  97. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  98. Fermi GRB 260115A: Global MASTER-Net observations report
  99. GRB 251222A: radio detection with the VLA
  100. GRB 260114A: VLT/HAWK-I near-infrared upper limits

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