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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"

23838 results found.

  1. EP250402a: Einstein Probe detection of a fast X-ray transient
  2. GRB 250402A: SVOM detection of a burst
  3. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  4. GRB 250329B: Swift/UVOT Upper Limit
  5. GRB 250329A: Swift/UVOT Upper Limit
  6. GRB 250327B: Swift/UVOT Detection
  7. GRB 250327A: Swift/UVOT Upper Limits
  8. GRB 250331E: SVOM/GRM observation
  9. GRB250331D: AbAO optical observations
  10. GRB 250331D: Fermi GBM observation
  11. GRB 250331C: Swift/UVOT Upper Limits
  12. GRB 250331B: Swift/UVOT Upper Limits
  13. GRB 250328A: AbAO AS-32 Optical Observations
  14. GRB 250331D: Swift-XRT observations
  15. GRB 250331C: Swift-XRT refined Analysis
  16. GRB 250331B: Swift-XRT refined Analysis
  17. GRB 250331B: Swift-XRT refined Analysis
  18. GRB 250330B: SVOM/GRM observation of a short burst
  19. Fermi GRB 250331E: Global MASTER-Net observations report
  20. Fermi GRB 250331D: Global MASTER-Net observations report
  21. GRB 250331E: Fermi GBM Final Real-time Localization
  22. GRB 250327A Swift-BAT refined analysis
  23. Fermi trigger No 765078057: Global MASTER-Net observations report
  24. GRB 250329B: CAHA 2.2m telescope optical limit
  25. GRB 250331D: Swift ToO observations
  26. Swift GRB 250331C: Global MASTER-Net observations report
  27. Swift GRB 250331B: Global MASTER-Net observations report
  28. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  29. GRB 250320C : SVOM detection of a burst through offline search
  30. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  31. GRB 250330A: VLT/FORS2 Afterglow Detection
  32. GRB20250327B: 45th Parallel Observatory upper limit
  33. GRB 250328A: Swift/UVOT Detection
  34. GRB 250328A: Swift-XRT refined Analysis
  35. SVOM/sb25033102 is a false trigger
  36. GRB 250330A: Fermi GBM Observation
  37. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  38. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  39. GRB 250331D: Fermi GBM Final Real-time Localization
  40. GRB 250331C: Swift detection of a burst
  41. GRB 250331B: Swift detection of a burst
  42. GRB 250330A: SVOM/VT optical upper limit
  43. SVOM/sb25033102: SVOM detection of an X-ray transient
  44. Fermi GRB 250330B: Global MASTER-Net observations report
  45. GRB 250330B: Fermi GBM Final Real-time Localization
  46. Fermi GRB 250330A: Global MASTER-Net observations report
  47. GRB 250330A: BOOTES-7 early optical upper limit
  48. GRB 250330A: Swift/UVOT Upper Limits
  49. GRB 250330A: Swift-XRT afterglow detection
  50. GRB 250328A: 1.6m Mephisto optical observations
  51. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  52. GRB 250330A: Fermi GBM Final Localization
  53. IceCube Alert 250330.35: Global MASTER-Net observations report
  54. GRB 250330A: VLT/FORS2 Optical Observations
  55. GRB 250330A: Prompt Swift-XRT position
  56. GRB 250329B: Swift-XRT afterglow detection
  57. GRB 250330A: Swift detection of a burst
  58. Swift GRB250330.26: Global MASTER-Net observations report
  59. GRB 250329B: SVOM/C-GFT optical upper limit
  60. GRB 250329B: SVOM/VT optical upper limit
  61. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  62. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  63. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  64. GRB250329A: REM optical afterglow detection
  65. GRB 250329B: SVOM detection of a faint transient
  66. GRB 250329A: Swift-XRT afterglow detection
  67. GRB 250329A: Fading optical counterpart detection by LCO.
  68. GRB 250328A: SVOM/C-GFT optical upper limit
  69. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  70. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  71. GRB 250329A: VLT/X-shooter redshift z = 2.921
  72. GRB 250329A: SVOM detection of a burst
  73. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  74. GRB 250327B: MASTER detection of OT rebrightening
  75. GRB 250327B: LCO optical counterpart detection
  76. GRB 250328A: SVOM detection of a burst
  77. GRB 250327B: CrAO and SAO RAS Optical Observations
  78. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  79. GRB 250327b: Liverpool Telescope optical observations
  80. GRB 250322A: GRANDMA/TNOT optical upper limits
  81. GRB 250327A: SVOM/VT upper limits on the XRT position
  82. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  83. GRB 250327B: Las Cumbres optical counterpart detection
  84. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  85. GRB 250327B: 1.6m Mephisto optical observations
  86. GRB 250327B: NOT spectroscopic redshift z = 3.035
  87. GRB 250327A: Swift-XRT refined Analysis
  88. GRB 250327B: GOTO optical counterpart detection
  89. GRB 250327B: SAO RAS optical candidate
  90. GRB 250327B: SVOM detection of a burst
  91. GRB 250327A: J-band observations with WINTER
  92. GRB 250327A: SVOM/VT optical candidate
  93. GRB 250327A: Fermi GBM observation
  94. Fermi GRB 250327A: Global MASTER-Net observations report
  95. Swift GRB 250327A: Global MASTER-Net observations report
  96. GRB 250327A: DDOTI Optical Observations
  97. GRB 250327A: COLIBRÍ optical upper limit
  98. GRB 250327A: Swift detection of a burst
  99. GRB 250327A: Fermi GBM Final Real-time Localization
  100. Fermi trigger No 764700395: Global MASTER-Net observations report

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