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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"

14851 results found.

  1. GRB 250404A / EP250404a: NOT optical observations
  2. GRB 250331D: Swift-XRT afterglow detection
  3. GRB 250404B: AstroSat CZTI detection of a short burst
  4. GRB 250403A: AstroSat CZTI detection
  5. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  6. EP250404a: REM optical/NIR observations
  7. EP250404a: Seimei/TriCCS optical counterpart detection
  8. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  9. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  10. EP250404a: LCO optical counterpart detection
  11. EP250404a: Xinglong decaying optical counterpart
  12. GRB 250403A: Montarrenti Observatory optical detection
  13. GRB 250404A: Fermi GBM Detection
  14. EP250404a: AKO Optical Afterglow Detection
  15. EP250404a: LAST detection of optical counterpart
  16. EP250404a: Xinglong-2.16m spectroscopic redshift
  17. GRB 250327B: VIRT Optical Upper Limit
  18. EP250404a: Mephisto multi-band optical detection
  19. EP250404a: BOOTES-4/JGT optical afterglow detection
  20. EP250404a: Nanshan/HMT optical counterpart detection
  21. EP250404a: Einstein Probe detection of an X-ray transient
  22. GRB 250404A: Fermi GBM Final Real-time Localization
  23. GRB 250403A: Swift/UVOT Detection
  24. GRB 250402A: Swift/UVOT Upper Limits
  25. GRB 250403A: REM NIR afterglow detection
  26. GRB 250403A: LCO optical counterpart detection
  27. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  28. GRB 250402A: EP-FXT afterglow detection
  29. GRB 250403A: Optical counterpart detection by LCO.
  30. GRB 250322A: 10 GHz VLA radio upper limits
  31. GRB 250403A: 1.6m Mephisto multi-band optical detection
  32. GRB 250403A: GOTO detection of the optical afterglow
  33. GRB 250403A : SVOM detection of a burst
  34. GRB 250403A: Fermi GBM Final Real-time Localization
  35. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  36. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  37. GRB 250402A: LCO optical counterpart detection
  38. EP250402a: Einstein Probe detection of a fast X-ray transient
  39. GRB 250402B: AstroSat CZTI detection of a short burst
  40. GRB 250402A: SVOM detection of a burst
  41. GRB 250314A: ALMA detection
  42. GRB 250329A: Swift/UVOT Upper Limit
  43. GRB 250327B: Swift/UVOT Detection
  44. GRB 250219A: NOT candidate host galaxy detection
  45. GRB 250322B: GRBAlpha detection
  46. GRB 250322B possible detection by the AstroSat Satellite
  47. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  48. GRB 250330B: EIRSAT-1 GMOD Detection
  49. GRB 250331E: Fermi GBM Final Real-time Localization
  50. GRB 250329B: CAHA 2.2m telescope optical limit
  51. Konus-Wind detection of GRB 250327B
  52. GRB 250320C : SVOM detection of a burst through offline search
  53. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  54. GRB 250330A: VLT/FORS2 Afterglow Detection
  55. GRB 250328A: Swift/UVOT Detection
  56. GRB 250331D: Fermi GBM Final Real-time Localization
  57. GRB 250331C: Swift detection of a burst
  58. GRB 250331B: Swift detection of a burst
  59. GRB 250331A: MAXI/GSC detection
  60. SVOM/sb25033102: SVOM detection of an X-ray transient
  61. GRB 250314A: VLA detection
  62. GRB 250330B: Fermi GBM Final Real-time Localization
  63. GRB 250330A: BOOTES-7 early optical upper limit
  64. GRB 250330A: Swift-XRT afterglow detection
  65. GRB 250328A: 1.6m Mephisto optical observations
  66. GRB 250330A: Fermi GBM Final Localization
  67. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 250329B: Swift-XRT afterglow detection
  69. GRB 250330A: Swift detection of a burst
  70. GRB 250327B: ALMA detection
  71. GRB 250327B: VLA detection
  72. GRB250329A: REM optical afterglow detection
  73. GRB 250329B: SVOM detection of a faint transient
  74. GRB 250329A: Swift-XRT afterglow detection
  75. GRB 250329A: Fading optical counterpart detection by LCO.
  76. GRB 250329A: VLT/X-shooter redshift z = 2.921
  77. GRB 250329A: SVOM detection of a burst
  78. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  79. GRB 250327B: MASTER detection of OT rebrightening
  80. GRB 250327B: LCO optical counterpart detection
  81. GRB 250328A: SVOM detection of a burst
  82. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  83. EP250315a: Pan-STARRS r and i-band imaging and photometry
  84. GRB 250327b: Liverpool Telescope optical observations
  85. GRB 250327B: Las Cumbres optical counterpart detection
  86. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  87. GRB 250327B: NOT spectroscopic redshift z = 3.035
  88. GRB 250327B: GOTO optical counterpart detection
  89. GRB 250327B: SVOM detection of a burst
  90. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  91. GRB 250327A: DDOTI Optical Observations
  92. GRB 250327A: Swift detection of a burst
  93. GRB 250327A: Fermi GBM Final Real-time Localization
  94. Konus-Wind detection of GRB 250322A (short)
  95. IPN triangulation of GRB 250322B
  96. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  97. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  98. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  99. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  100. EP250321a: TNOT Observation of Optical Counterpart

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