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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"

14328 results found.

  1. GRB 250402A: Swift/UVOT Upper Limits
  2. GRB 250403A: REM NIR afterglow detection
  3. GRB 250403A: LCO optical counterpart detection
  4. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  5. GRB 250402A: EP-FXT afterglow detection
  6. GRB 250403A: Optical counterpart detection by LCO.
  7. GRB 250322A: 10 GHz VLA radio upper limits
  8. GRB 250403A: 1.6m Mephisto multi-band optical detection
  9. GRB 250403A: GOTO detection of the optical afterglow
  10. GRB 250403A : SVOM detection of a burst
  11. GRB 250403A: Fermi GBM Final Real-time Localization
  12. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  13. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  14. GRB 250402A: LCO optical counterpart detection
  15. EP250402a: Einstein Probe detection of a fast X-ray transient
  16. GRB 250402B: AstroSat CZTI detection of a short burst
  17. GRB 250402A: SVOM detection of a burst
  18. GRB 250314A: ALMA detection
  19. GRB 250329A: Swift/UVOT Upper Limit
  20. GRB 250327B: Swift/UVOT Detection
  21. GRB 250219A: NOT candidate host galaxy detection
  22. GRB 250322B: GRBAlpha detection
  23. GRB 250322B possible detection by the AstroSat Satellite
  24. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  25. GRB 250330B: EIRSAT-1 GMOD Detection
  26. GRB 250331E: Fermi GBM Final Real-time Localization
  27. GRB 250329B: CAHA 2.2m telescope optical limit
  28. Konus-Wind detection of GRB 250327B
  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. GRB 250328A: Swift/UVOT Detection
  33. GRB 250331D: Fermi GBM Final Real-time Localization
  34. GRB 250331C: Swift detection of a burst
  35. GRB 250331B: Swift detection of a burst
  36. GRB 250331A: MAXI/GSC detection
  37. SVOM/sb25033102: SVOM detection of an X-ray transient
  38. GRB 250314A: VLA detection
  39. GRB 250330B: Fermi GBM Final Real-time Localization
  40. GRB 250330A: BOOTES-7 early optical upper limit
  41. GRB 250330A: Swift-XRT afterglow detection
  42. GRB 250328A: 1.6m Mephisto optical observations
  43. GRB 250330A: Fermi GBM Final Localization
  44. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  45. GRB 250329B: Swift-XRT afterglow detection
  46. GRB 250330A: Swift detection of a burst
  47. GRB 250327B: ALMA detection
  48. GRB 250327B: VLA detection
  49. GRB250329A: REM optical afterglow detection
  50. GRB 250329B: SVOM detection of a faint transient
  51. GRB 250329A: Swift-XRT afterglow detection
  52. GRB 250329A: Fading optical counterpart detection by LCO.
  53. GRB 250329A: VLT/X-shooter redshift z = 2.921
  54. GRB 250329A: SVOM detection of a burst
  55. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  56. GRB 250327B: MASTER detection of OT rebrightening
  57. GRB 250327B: LCO optical counterpart detection
  58. GRB 250328A: SVOM detection of a burst
  59. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  60. EP250315a: Pan-STARRS r and i-band imaging and photometry
  61. GRB 250327b: Liverpool Telescope optical observations
  62. GRB 250327B: Las Cumbres optical counterpart detection
  63. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  64. GRB 250327B: NOT spectroscopic redshift z = 3.035
  65. GRB 250327B: GOTO optical counterpart detection
  66. GRB 250327B: SVOM detection of a burst
  67. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  68. GRB 250327A: DDOTI Optical Observations
  69. GRB 250327A: Swift detection of a burst
  70. GRB 250327A: Fermi GBM Final Real-time Localization
  71. Konus-Wind detection of GRB 250322A (short)
  72. IPN triangulation of GRB 250322B
  73. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  74. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  75. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  76. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  77. EP250321a: TNOT Observation of Optical Counterpart
  78. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  79. SVOM/sb25032302: SVOM detection of a long X-ray transient
  80. GRB 250322A: AstroSat CZTI detection of a short burst
  81. GRB 250322B: AstroSat CZTI detection of a bright long burst
  82. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  83. EP250321a: Liverpool Telescope optical follow-up
  84. GRB 250322A: Swift detection of a short burst
  85. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  86. GRB 250225B: GECAM-A detection
  87. GRB 250312A: GECAM-A detection
  88. EP250321a: WFST optical observations
  89. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  90. GRB 250321C: Fermi GBM Final Real-time Localization
  91. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  92. GRB 250320B: Fermi-LAT detection
  93. GRB 250321B: SVOM detection of a sub-threshold transient event
  94. EP 250321A: Optical counterpart detection by LCO.
  95. EP250321a: LCO optical counterpart detection
  96. EP250321a: Swift-XRT detection of an X-ray source
  97. EP250321a: VLT/X-shooter redshift z = 4.368
  98. GRB 250320B: AstroSat CZTI detection
  99. EP250321a: REM optical/NIR afterglow detection
  100. EP250321a: BOOTES-5/JGT optical afterglow detection

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