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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"

19549 results found.

  1. IceCube-250406A: Swift-XRT observations
  2. GRB 250407A: LCO detection of a fading optical counterpart
  3. GRB 250407A: SVOM/GRM observation of a bright long burst
  4. GRB 250407A: EP-WXT afterglow detection
  5. EP250407a: EP-WXT detection of a fast X-ray transient
  6. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  7. GRB 250407A: KAIT Optical Afterglow Candidate
  8. IceCube-250406A: No candidates from the Zwicky Transient Facility
  9. GRB 250407A: Swift-XRT afterglow detection
  10. GRB 250407A: Swift ToO observations
  11. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  12. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  13. IPN triangulation of GRB 250406B (short/hard)
  14. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  15. IceCube 250406.951: DDOTI Optical Observations
  16. GRB 250406A: AstroSat CZTI detection
  17. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  18. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  19. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  20. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  21. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  22. Konus-Wind detection of GRB 250404A / EP250404a
  23. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  24. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  25. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  26. EP250402a: Optical upper limit with PD 1.3m observations
  27. GRB 250404A / EP250404a: NOT optical observations
  28. GRB 250331D: Swift-XRT afterglow detection
  29. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  30. EP250404a: REM optical/NIR observations
  31. EP250404a: Seimei/TriCCS optical counterpart detection
  32. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  33. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  34. EP250404a: LCO optical counterpart detection
  35. EP250404a: Xinglong decaying optical counterpart
  36. GRB 250403A: Montarrenti Observatory optical detection
  37. GRB 250403A: KAIT optical observations
  38. EP250404a: AKO Optical Afterglow Detection
  39. EP250404a: LAST detection of optical counterpart
  40. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  41. GRB 250327B: VIRT Optical Upper Limit
  42. EP250404a: Mephisto multi-band optical detection
  43. EP250321A: J band upper limit by SYSU 80cm telescope
  44. EP250404a: Nanshan/HMT optical counterpart detection
  45. EP250404a: Einstein Probe detection of an X-ray transient
  46. GRB 250403A: Swift/UVOT Detection
  47. GRB 250402A: Swift/UVOT Upper Limits
  48. EP250402a: Optical upper limit with Kinder observations
  49. GRB 250403A: REM NIR afterglow detection
  50. GRB 250403A: LCO optical counterpart detection
  51. GRB 250403A: JinShan optical observations
  52. GRB 250403A: Optical counterpart detection by LCO.
  53. GRB 250403A: GMG Optical Observation
  54. GRB 250403A: 1.6m Mephisto multi-band optical detection
  55. GRB 250403A: SVOM/C-GFT optical observations
  56. GRB 250403A : SVOM detection of a burst
  57. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  58. GRB 250402A: REM optical/NIR upper limits
  59. GRB 250402A: LCO optical counterpart detection
  60. EP250402a: Einstein Probe detection of a fast X-ray transient
  61. GRB 250402B: AstroSat CZTI detection of a short burst
  62. GRB 250402A: SVOM/VT optical counterpart
  63. GRB 250402A: SVOM detection of a burst
  64. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  65. GRB 250329B: Swift/UVOT Upper Limit
  66. GRB 250329A: Swift/UVOT Upper Limit
  67. GRB 250327B: Swift/UVOT Detection
  68. GRB 250327A: Swift/UVOT Upper Limits
  69. GRB 250331E: SVOM/GRM observation
  70. GRB 250327B: Kilonova-Catcher Observations
  71. GRB 250331C: Swift/UVOT Upper Limits
  72. GRB 250331B: Swift/UVOT Upper Limits
  73. GRB 250328A: AbAO AS-32 Optical Observations
  74. GRB 250219A: NOT candidate host galaxy detection
  75. GRB 250330B: SVOM/GRM observation of a short burst
  76. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  77. GRB 250331D: Swift ToO observations
  78. GRB 250331C: Enhanced Swift-XRT position
  79. GRB 250331B: Enhanced Swift-XRT position
  80. GRB 250330A: VLT/FORS2 Afterglow Detection
  81. GRB20250327B: 45th Parallel Observatory upper limit
  82. GRB 250328A: Swift/UVOT Detection
  83. GRB 250328A: Swift-XRT refined Analysis
  84. GRB 250330A: Fermi GBM Observation
  85. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  86. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  87. GRB 250331C: Swift detection of a burst
  88. GRB 250331B: Swift detection of a burst
  89. SVOM/sb25033102: SVOM detection of an X-ray transient
  90. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  91. GRB 250330A: Swift/UVOT Upper Limits
  92. GRB 250330A: Swift-XRT afterglow detection
  93. GRB 250328A: 1.6m Mephisto optical observations
  94. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  95. GRB 250330A: VLT/FORS2 Optical Observations
  96. GRB 250329B: Swift-XRT afterglow detection
  97. GRB 250330A: Swift detection of a burst
  98. GRB 250329B: SVOM/C-GFT optical upper limit
  99. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  100. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations

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