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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"

14824 results found.

  1. EP250806a: Einstein Probe detection of an X-ray transient
  2. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. GRB 250806A: SVOM detection of a soft burst
  4. GRB 250804C: AstroSat CZTI detection of a long burst
  5. GRB 250805A: TRT optical upper limits
  6. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  7. GRB 250805A: Swift detection of a burst
  8. GRB 250804A: Fermi GBM Final Localization
  9. EP250802a: additional Liverpool Telescope upper limits
  10. EP250802a: Einstein Probe detection of an X-ray transient
  11. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  12. EP250730a: Einstein Probe detection of an X-ray transient
  13. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  14. GRB 250725A: AstroSat CZTI detection
  15. GRB 250725A: PRIME near-infrared observations
  16. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  17. GRB: Clarification on Gamma-Ray Burst Naming Convention
  18. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  19. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  20. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  21. GRB 250727A: AST3-2 Upper limit
  22. GRB 250727A: EP-FXT counterpart detection
  23. GRB 250727A: SVOM detection of a burst
  24. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  25. Konus-Wind detection of GRB 250725A
  26. GRB 250725A: Fermi-LAT detection
  27. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  28. GRB 250725A: BOOTES-7 early optical detection
  29. GRB 250725A: SVOM/VT optical candidate
  30. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  31. GRB 250725A: Swift detection of a burst
  32. Swift GRB 250725A: Global MASTER-Net OT detection
  33. GRB 250725A: Fermi GBM Final Real-time Localization
  34. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  35. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  36. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  37. GRB 250723B: Fermi GBM Final Real-time Localization
  38. GRB 250723A: Fermi GBM Final Real-time Localization
  39. GRB 250722A: Fermi GBM Final Real-time Localization
  40. GRB 250721A: MAXI/GSC detection
  41. GRB 250721A: Fermi GBM Final Localization
  42. GRB 250720B: Fermi GBM Final Localization Correction
  43. GRB 250720A: Fermi GBM Final Localization
  44. GRB 250718B: Fermi GBM Final Localization Correction
  45. GRB 250718B: Fermi GBM Final Real-time Localization
  46. Konus-Wind detection of GRB 250716A
  47. GRB 250716A: Swift-XRT afterglow detection
  48. GRB 250717B: Fermi GBM Final Real-time Localization
  49. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  50. GRB 250717A: Fermi GBM Final Real-time Localization
  51. GRB 250716A: Fermi GBM Final Real-time Localization
  52. GRB 250715A: Fermi GBM Final Real-time Localization
  53. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  54. GRB 250714A: Fermi GBM Final Real-time Localization
  55. GRB 250706B/C: 7DT Follow-up Observations
  56. GRB 250713A: EP-FXT counterpart detection
  57. GRB 250713A: JinShan optical upper limits
  58. GRB 250713A: SVOM detection of a long burst
  59. EP250711a: NOT optical counterpart candidate
  60. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  61. GRB 250711A: Fermi GBM Final Real-time Localization
  62. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  63. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  64. GRB 250702B,D,E / EP250702a: ALMA detection
  65. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  66. GRB 250709A: Fermi GBM Final Localization
  67. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  68. GRB 250706B/C: Insight-HXMT detection
  69. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  70. EP250704a/GRB 250704B: 10 GHz VLA detection
  71. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  72. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 250704B / EP250704a: VLA radio detection
  74. GRB 250708A: Fermi GBM Final Real-time Localization
  75. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  76. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  77. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  78. GRB 250702F: radio detection with the VLA
  79. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  80. GRB 250706B/C: Fermi-LAT detection
  81. GRB 250706B: Swift/UVOT Detection
  82. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  83. GRB 250702F: GRANDMA observations
  84. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  85. IceCube-250416A: DDOTI Optical Upper Limit
  86. GRB 250706A: JinShan optical upper limits
  87. GRB 250706A: SAO RAS optical observations
  88. EP250704A: NOWT Detection
  89. GRB250706B: Swift-XRT counterpart detection
  90. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  91. GRB 250706B: TRT bright optical counterpart detection
  92. GRB 250706B: SVOM detection of a long burst
  93. GRB 250706A: Swift detection of a burst
  94. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  95. GRB 250703A: EIRSAT-1 GMOD Detection
  96. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  97. GRB 250704A: Swift/UVOT Detection
  98. GRB 250704B: Insight-HXMT detection
  99. Konus-Wind detection of GRB 250703A
  100. IPN triangulation of GRB 250703A

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