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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"

27557 results found.

  1. GRB 250322A: 10 GHz VLA radio upper limits
  2. GRB 250403A: 1.6m Mephisto multi-band optical detection
  3. GRB 250403A: GOTO detection of the optical afterglow
  4. GRB 250402A: Swift-XRT observations
  5. GRB 250403A : SVOM detection of a burst
  6. GRB 250403A: Fermi GBM Final Real-time Localization
  7. GRB 250225B: VLT host galaxy redshift z = 0.950
  8. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  9. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  10. GRB 250402A: REM optical/NIR upper limits
  11. GRB 250402A: LCO optical counterpart detection
  12. GRB 250402A: refined SVOM/MXT data analysis
  13. EP250402a: Einstein Probe detection of a fast X-ray transient
  14. GRB 250402B: AstroSat CZTI detection of a short burst
  15. GRB 250402A: SVOM detection of a burst
  16. GRB 250314A: ALMA detection
  17. GRB 250329B: Swift/UVOT Upper Limit
  18. GRB 250329A: Swift/UVOT Upper Limit
  19. GRB 250327B: Swift/UVOT Detection
  20. GRB 250327A: Swift/UVOT Upper Limits
  21. GRB 250327B: Kilonova-Catcher Observations
  22. GRB250331D: AbAO optical observations
  23. GRB 250331C: Swift/UVOT Upper Limits
  24. GRB 250331B: Swift/UVOT Upper Limits
  25. GRB 250328A: AbAO AS-32 Optical Observations
  26. GRB 250219A: NOT candidate host galaxy detection
  27. GRB 250322B: GRBAlpha detection
  28. GRB 250331D: Swift-XRT observations
  29. GRB 250331C: Swift-XRT refined Analysis
  30. GRB 250331B: Swift-XRT refined Analysis
  31. GRB 250331B: Swift-XRT refined Analysis
  32. GRB 250322B possible detection by the AstroSat Satellite
  33. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  34. GRB 250330B: EIRSAT-1 GMOD Detection
  35. GRB 250331E: Fermi GBM Final Real-time Localization
  36. GRB 250329B: CAHA 2.2m telescope optical limit
  37. GRB 250331D: Swift ToO observations
  38. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  39. Konus-Wind detection of GRB 250327B
  40. GRB 250331C: Enhanced Swift-XRT position
  41. GRB 250331B: Enhanced Swift-XRT position
  42. GRB 250320C : SVOM detection of a burst through offline search
  43. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  44. GRB 250329B: Swift-XRT confirmation of fading
  45. GRB 250330A: VLT/FORS2 Afterglow Detection
  46. GRB20250327B: 45th Parallel Observatory upper limit
  47. GRB 250328A: Swift/UVOT Detection
  48. GRB 250328A: Swift-XRT refined Analysis
  49. GRB 250330A: Fermi GBM Observation
  50. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  51. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  52. GRB 250331D: Fermi GBM Final Real-time Localization
  53. GRB 250331C: Prompt enhanced Swift-XRT position
  54. GRB 250331C: Swift detection of a burst
  55. GRB 250331B: Swift detection of a burst
  56. GRB 250330A: SVOM/VT optical upper limit
  57. GRB 250331A: MAXI/GSC detection
  58. SVOM/sb25033102: SVOM detection of an X-ray transient
  59. GRB 250314A: VLA detection
  60. GRB 250330B: Fermi GBM Final Real-time Localization
  61. GRB 250330A: BOOTES-7 early optical upper limit
  62. GRB 250330A: Swift/UVOT Upper Limits
  63. GRB 250330A: Swift-XRT afterglow detection
  64. GRB 250328A: 1.6m Mephisto optical observations
  65. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  66. GRB 250330A: Fermi GBM Final Localization
  67. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 250330A: VLT/FORS2 Optical Observations
  69. GRB 250330A: Prompt Swift-XRT position
  70. GRB 250329B: Swift-XRT afterglow detection
  71. GRB 250330A: Swift detection of a burst
  72. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  73. GRB 250329B: SVOM/C-GFT optical upper limit
  74. GRB 250327B: ALMA detection
  75. GRB 250327B: VLA detection
  76. GRB 250329B: SVOM/VT optical upper limit
  77. GRB250329A: REM optical afterglow detection
  78. GRB 250329B: SVOM detection of a faint transient
  79. GRB 250329A: Swift-XRT afterglow detection
  80. GRB 250329A: Fading optical counterpart detection by LCO.
  81. GRB 250328A: SVOM/C-GFT optical upper limit
  82. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  83. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  84. GRB 250329A: VLT/X-shooter redshift z = 2.921
  85. GRB 250329A: SVOM detection of a burst
  86. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  87. GRB 250327B: MASTER detection of OT rebrightening
  88. GRB 250327B: LCO optical counterpart detection
  89. GRB 250328A: SVOM detection of a burst
  90. GRB 250327B: CrAO and SAO RAS Optical Observations
  91. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  92. EP250315a: Pan-STARRS r and i-band imaging and photometry
  93. GRB 250327b: Liverpool Telescope optical observations
  94. GRB 250322A: GRANDMA/TNOT optical upper limits
  95. GRB 250327A: SVOM/VT upper limits on the XRT position
  96. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  97. GRB 250327B: Las Cumbres optical counterpart detection
  98. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  99. GRB 250327B: 1.6m Mephisto optical observations
  100. GRB 250327B: NOT spectroscopic redshift z = 3.035

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