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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"

20364 results found.

  1. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  2. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  3. GRB 250419A: SVOM detection of a soft burst
  4. EP250416a: refined EP-WXT and EP-FXT analysis
  5. EP20250416a: Swift/XRT counterpart detection
  6. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  7. IceCube-250416A: DDOTI Optical Observations
  8. EP250416a: Gemini South-GMOS optical counterpart
  9. SVOM/sb25041603 is not a GRB
  10. EP250416a: Einstein Probe detection of an X-ray transient
  11. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  12. IceCube 250414.324: DDOTI Optical Observations
  13. GRB 250413A: AstroSat CZTI detection
  14. GRB 250412A: AstroSat CZTI detection
  15. EP250404a: Nanshan 0.43m Telescope optical observatios
  16. GRB 250411A: DDOTI Optical Observations
  17. GRB 250314A: e-MERLIN observations
  18. GRB 250407A: Mondy and AbAO Optical Observations
  19. EP250227a: Further NOT optical observations
  20. IceCube-250406A: Swift-XRT observations
  21. GRB 250407A: LCO detection of a fading optical counterpart
  22. Fermi-LAT gamma-ray observations of IceCube-250406A
  23. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  24. Konus-Wind detection of GRB 250407A
  25. GRB 250407A: SVOM/GRM observation of a bright long burst
  26. GRB 250407A: EP-WXT afterglow detection
  27. EP250407a: EP-WXT detection of a fast X-ray transient
  28. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  29. GRB 250407A: KAIT Optical Afterglow Candidate
  30. IceCube-250406A: No candidates from the Zwicky Transient Facility
  31. GRB 250407A: Swift-XRT afterglow detection
  32. GRB 250407A: SRG/ART-XC afterglow detection
  33. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  34. IPN triangulation of GRB 250406B (short/hard)
  35. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  36. IceCube 250406.951: DDOTI Optical Observations
  37. GRB 250406A: AstroSat CZTI detection
  38. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  39. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  40. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  41. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  42. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  43. Konus-Wind detection of GRB 250404A / EP250404a
  44. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  46. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  47. EP250402a: Optical upper limit with PD 1.3m observations
  48. GRB 250404A / EP250404a: NOT optical observations
  49. GRB 250331D: Swift-XRT afterglow detection
  50. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  51. EP250404a: REM optical/NIR observations
  52. EP250404a: Seimei/TriCCS optical counterpart detection
  53. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  54. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  55. EP250404a: LCO optical counterpart detection
  56. EP250404a: Xinglong decaying optical counterpart
  57. GRB 250403A: Montarrenti Observatory optical detection
  58. GRB 250403A: KAIT optical observations
  59. EP250404a: AKO Optical Afterglow Detection
  60. EP250404a: LAST detection of optical counterpart
  61. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  62. GRB 250327B: VIRT Optical Upper Limit
  63. EP250404a: Mephisto multi-band optical detection
  64. EP250321A: J band upper limit by SYSU 80cm telescope
  65. EP250404a: BOOTES-4/JGT optical afterglow detection
  66. EP250404a: Nanshan/HMT optical counterpart detection
  67. EP250404a: Einstein Probe detection of an X-ray transient
  68. GRB 250404A: Fermi GBM Final Real-time Localization
  69. GRB 250403A: Swift/UVOT Detection
  70. GRB 250402A: Swift/UVOT Upper Limits
  71. EP250402a: Optical upper limit with Kinder observations
  72. GRB 250403A: REM NIR afterglow detection
  73. GRB 250403A: LCO optical counterpart detection
  74. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  75. GRB 250403A: JinShan optical observations
  76. GRB 250403A: Optical counterpart detection by LCO.
  77. GRB 250322A: 10 GHz VLA radio upper limits
  78. GRB 250402A: NUTTelA-TAO Early Optical Limits
  79. GRB 250403A: GMG Optical Observation
  80. GRB 250403A: 1.6m Mephisto multi-band optical detection
  81. GRB 250403A: SVOM/C-GFT optical observations
  82. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  83. GRB 250402A: REM optical/NIR upper limits
  84. GRB 250402A: LCO optical counterpart detection
  85. EP250402a: Einstein Probe detection of a fast X-ray transient
  86. GRB 250402A: SVOM/VT optical counterpart
  87. GRB 250402A: SVOM detection of a burst
  88. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  89. GRB 250329B: Swift/UVOT Upper Limit
  90. GRB 250329A: Swift/UVOT Upper Limit
  91. GRB 250327B: Swift/UVOT Detection
  92. GRB 250327A: Swift/UVOT Upper Limits
  93. GRB 250331E: SVOM/GRM observation
  94. GRB 250327B: Kilonova-Catcher Observations
  95. GRB250331D: AbAO optical observations
  96. GRB 250331C: Swift/UVOT Upper Limits
  97. GRB 250331B: Swift/UVOT Upper Limits
  98. GRB 250328A: AbAO AS-32 Optical Observations
  99. GRB 250219A: NOT candidate host galaxy detection
  100. GRB 250331D: Swift-XRT observations

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