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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').

18344 results found.

  1. GRB 250424A: SVOM/GRM observation of a long burst
  2. GRB 250424A: PRIME near-infrared detection
  3. GRB 250424A: WINTER J-band detection
  4. GRB 250424A: EIRSAT-1 GMOD Detection
  5. GRB 250424A: Swift/UVOT Detection
  6. Konus-Wind detection of GRB 250424A
  7. GRB 250424A: Skynet Optical Observations
  8. GRB 250424A: Kilonova-Catcher optical afterglow detection
  9. GRB 250424A: Swift-XRT refined Analysis
  10. GRB 250424A: Enhanced Swift-XRT position
  11. GRB 250424A: AstroSat CZTI detection of a bright long burst
  12. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  13. GRB 250424A: BlackGEM optical afterglow detection
  14. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  15. GRB 250424A: likely host galaxy
  16. GRB 250424A: DDOTI Afterglow Detection
  17. GRB 250424A: REM optical/NIR afterglow detection
  18. GRB 250424A: Swift detection of a burst with an optical counterpart
  19. Swift GRB250424A: Global MASTER-Net observations report
  20. Swift GRB250424A: Global MASTER-Net OT detection
  21. SVOM/sb25042207: XRT observations
  22. EP250421a: NOT optical observations
  23. EP250421a: Swift/XRT counterpart detection
  24. GRB 250419A: Swift/UVOT Follow up
  25. GRB 250419A: LCO optical afterglow multi-band observations
  26. GRB 250419A: Mondy and AbAO Optical Observations
  27. GRB 250419A: Swift-XRT localisation
  28. GRB 250419A: Swift-XRT refined Analysis
  29. EP250416a: Swift/XRT counterpart fading
  30. EP20250416a: Swift/XRT counterpart detection
  31. GRB 250407A: Mondy and AbAO Optical Observations
  32. IceCube-250406A: Swift-XRT observations
  33. IPN triangulation of GRB 250407A
  34. GRB 250407A: LCO detection of a fading optical counterpart
  35. EP250407a: Swift-XRT observations
  36. Konus-Wind detection of GRB 250407A
  37. GRB 250407A: SVOM/GRM observation of a bright long burst
  38. GRB 250407A: EP-WXT afterglow detection
  39. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  40. GRB 250407A: Fermi GBM Detection
  41. GRB 250407A: Swift-XRT afterglow detection
  42. GRB 250407A: Swift ToO observations
  43. GRB 250407A: SRG/ART-XC afterglow detection
  44. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  45. IPN triangulation of GRB 250406B (short/hard)
  46. GRB 250331D: Swift-XRT afterglow detection
  47. GRB 250403A: Montarrenti Observatory optical detection
  48. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  49. GRB 250331C Swift-BAT refined analysis
  50. GRB 250331B Swift-BAT refined analysis
  51. GRB 250330A Swift-BAT refined analysis
  52. EP250321A: J band upper limit by SYSU 80cm telescope
  53. GRB 250403A: Swift/UVOT Detection
  54. GRB 250402A: Swift/UVOT Upper Limits
  55. GRB 250403A: LCO optical counterpart detection
  56. GRB 250402A: EP-FXT afterglow detection
  57. GRB 250403A: Swift-XRT observations
  58. GRB 250402A: Swift-XRT observations
  59. GRB 250225B: VLT host galaxy redshift z = 0.950
  60. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  61. GRB 250329B: Swift/UVOT Upper Limit
  62. GRB 250329A: Swift/UVOT Upper Limit
  63. GRB 250327B: Swift/UVOT Detection
  64. GRB 250327A: Swift/UVOT Upper Limits
  65. GRB250331D: AbAO optical observations
  66. GRB 250331D: Fermi GBM observation
  67. GRB 250331C: Swift/UVOT Upper Limits
  68. GRB 250331B: Swift/UVOT Upper Limits
  69. GRB 250331D: Swift-XRT observations
  70. GRB 250331C: Swift-XRT refined Analysis
  71. GRB 250331B: Swift-XRT refined Analysis
  72. GRB 250331B: Swift-XRT refined Analysis
  73. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  74. GRB 250327A Swift-BAT refined analysis
  75. GRB 250329B: CAHA 2.2m telescope optical limit
  76. GRB 250331D: Swift ToO observations
  77. Swift GRB 250331C: Global MASTER-Net observations report
  78. Swift GRB 250331B: Global MASTER-Net observations report
  79. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  80. GRB 250331C: Enhanced Swift-XRT position
  81. GRB 250331B: Enhanced Swift-XRT position
  82. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  83. GRB 250329B: Swift-XRT confirmation of fading
  84. GRB20250327B: 45th Parallel Observatory upper limit
  85. GRB 250328A: Swift/UVOT Detection
  86. GRB 250328A: Swift-XRT refined Analysis
  87. GRB 250330A: Fermi GBM Observation
  88. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  89. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  90. GRB 250331C: Prompt enhanced Swift-XRT position
  91. GRB 250331C: Swift detection of a burst
  92. GRB 250331B: Swift detection of a burst
  93. GRB 250330A: SVOM/VT optical upper limit
  94. GRB 250330A: BOOTES-7 early optical upper limit
  95. GRB 250330A: Swift/UVOT Upper Limits
  96. GRB 250330A: Swift-XRT afterglow detection
  97. GRB 250330A: Fermi GBM Final Localization
  98. GRB 250330A: Prompt Swift-XRT position
  99. GRB 250329B: Swift-XRT afterglow detection
  100. GRB 250330A: Swift detection of a burst

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