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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"

28048 results found.

  1. EP260128a: Global MASTER-Net observations report
  2. EP260128a: Einstein Probe detection of an X-ray transient
  3. Fermi GRB 260127A: Global MASTER-Net observations report
  4. GRB 260127A: Fermi GBM Observation
  5. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  6. GRB 260127A: COLIBRÍ optical observations
  7. EP260126a: Seimei/TriCCS optical upper limit
  8. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  9. GRB 260127A: Swift-XRT refined Analysis
  10. GRB 260127A: SVOM/C-GFT optical observations
  11. GRB 260127A: Enhanced Swift-XRT position
  12. Fermi GRB 260127B: Global MASTER-Net observations report
  13. Swift GRB 260127A: Global MASTER-Net observations report
  14. GRB 260127A: LCO optical afterglow discovery
  15. GRB 260127A: Swift detection of a burst
  16. GRB 260125A: Swift-XRT observations
  17. EP260126a: Optical upper limit with Kinder observations
  18. EP260126a: Liverpool Telescope optical upper limits
  19. EP260126a: Further NOT optical upper limits
  20. EP260126a: COLIBRÍ optical upper limits
  21. EP260126a: NOT optical observations
  22. EP260126a: Einstein Probe detection of a fast X-ray transient
  23. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  24. GRB 251222A: SVOM/ECLAIRs refined analysis
  25. GRB 260125A: GOTO candidate optical counterpart
  26. Fermi GRB 260125B: Global MASTER-Net observations report
  27. GRB 260114A: SVOM/VT optical upper limits
  28. GRB 260122B: Swift-BAT refined analysis
  29. GRB 260120B: SVOM/GRM observation
  30. Swift GRB260122.97: Global MASTER-Net observations report
  31. EP260119a: Assy AZT-20 optical observations
  32. EP260119a: Mondy and SAO RAS optical upper limits
  33. EP260119a: Xinglong optical upper limit
  34. Fermi GRB 260120C: Global MASTER-Net observations report
  35. GRB 260120B: Swift-BAT refined analysis
  36. GRB 260120B: Swift-XRT refined Analysis
  37. EP260116a: COLIBRÍ further observations
  38. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  39. GRB 260120B: Fermi GBM Observation
  40. EP260105a: GTC/HiPERCAM optical observations
  41. GRB 260120B: Swift/UVOT Detection
  42. GRB 260120B: COLIBRÍ optical upper limits
  43. SVOM GRB260121.06: Global MASTER-Net observations report
  44. GRB 260120B: Enhanced Swift-XRT position
  45. GRB 260120B: SVOM/C-GFT optical counterpart detection
  46. GRB 260101A: 239Alferov CubeSat detection
  47. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  48. GRB 260120B: Swift detection of a burst
  49. Swift GRB260120B: Global MASTER-Net observations report
  50. EP260119A: Mondy I-Band Observations
  51. Fermi trigger No 790601190: Global MASTER-Net observations report
  52. Fermi trigger No 790570272: Global MASTER-Net observations report
  53. GRB 260114A: Swift/UVOT Upper Limits
  54. EP260119a: Liverpool Telescope optical follow-up observations
  55. GRB 251202A: further radio observations with the VLA
  56. EP260119a: KAIT optical observations
  57. EP260119a: SVOM/VT optical observation
  58. EP260119a: NOT optical observations
  59. EP260119a: SAO RAS optical observations
  60. SVOM GRB260119.92: Global MASTER-Net observations report
  61. SVOM GRB260119.92: Global MASTER-Net observations report
  62. SVOM GRB260119.90: Global MASTER-Net observations report
  63. EP260116a: COLIBRÍ detection of a fading optical source
  64. GRB 260117A: Swift-XRT afterglow detection
  65. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  66. EP260119a: Global MASTER-Net observations report
  67. EP260119a: LCO optical observations
  68. GRB 260117A: ZTSh optical upper limit
  69. EP260119a: COLIBRÍ optical counterpart candidate
  70. EP260119a: EP-WXT detection of a fast X-ray transient
  71. Swift GRB260118.48: Global MASTER-Net observations report
  72. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. SVOM GRB260117.82: Global MASTER-Net observations report
  74. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  75. Swift trigger on the HMXB 1A 1118-61
  76. GRB 260117A: SVOM/VT optical candidate
  77. GRB 260117A: SVOM/C-GFT upper limit
  78. GRB 260117A: Swift-XRT observations
  79. GRB 260117A: SVOM detection of a long faint burst
  80. EP 260116a: COLIBRÍ optical upper limit
  81. Swift triggered on the HMXB 1A 1118-61
  82. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  83. EP260116a: Liverpool Telescope upper limits
  84. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  85. EP260116A: 1.3m DFOT optical upper limit
  86. GRB 260114A: VLT/MUSE spectroscopic observations
  87. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  88. EP260116a: Global MASTER-Net observations report
  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. IceCube Alert 260115.73: Global MASTER-Net observations report
  94. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  95. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  96. Fermi GRB 260115A: Global MASTER-Net observations report
  97. GRB 251222A: radio detection with the VLA
  98. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  99. GRB 260114A: Swift-XRT refined Analysis
  100. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy

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