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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 250427A: Swift-XRT refined Analysis
  2. GRB 250424A: LCO optical observation
  3. GRB 250424A: Swift-BAT refined analysis
  4. GRB 250424A: SVOM/GRM observation of a long burst
  5. GRB 250424A: PRIME near-infrared detection
  6. GRB 250424A: WINTER J-band detection
  7. GRB 250424A: EIRSAT-1 GMOD Detection
  8. GRB 250424A: Swift/UVOT Detection
  9. Konus-Wind detection of GRB 250424A
  10. GRB 250424A: Skynet Optical Observations
  11. GRB 250424A: Kilonova-Catcher optical afterglow detection
  12. GRB 250424A: Swift-XRT refined Analysis
  13. GRB 250424A: Enhanced Swift-XRT position
  14. GRB 250424A: AstroSat CZTI detection of a bright long burst
  15. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  16. GRB 250424A: BlackGEM optical afterglow detection
  17. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  18. GRB 250424A: likely host galaxy
  19. GRB 250424A: DDOTI Afterglow Detection
  20. GRB 250424A: REM optical/NIR afterglow detection
  21. GRB 250424A: Swift detection of a burst with an optical counterpart
  22. Swift GRB250424A: Global MASTER-Net observations report
  23. Swift GRB250424A: Global MASTER-Net OT detection
  24. SVOM/sb25042207: XRT observations
  25. EP250421a: NOT optical observations
  26. EP250421a: Swift/XRT counterpart detection
  27. GRB 250419A: Swift/UVOT Follow up
  28. GRB 250419A: LCO optical afterglow multi-band observations
  29. GRB 250419A: Mondy and AbAO Optical Observations
  30. GRB 250419A: Swift-XRT localisation
  31. GRB 250419A: Swift-XRT refined Analysis
  32. EP250416a: Swift/XRT counterpart fading
  33. EP20250416a: Swift/XRT counterpart detection
  34. GRB 250407A: Mondy and AbAO Optical Observations
  35. IceCube-250406A: Swift-XRT observations
  36. IPN triangulation of GRB 250407A
  37. GRB 250407A: LCO detection of a fading optical counterpart
  38. EP250407a: Swift-XRT observations
  39. Konus-Wind detection of GRB 250407A
  40. GRB 250407A: SVOM/GRM observation of a bright long burst
  41. GRB 250407A: EP-WXT afterglow detection
  42. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  43. GRB 250407A: Fermi GBM Detection
  44. GRB 250407A: Swift-XRT afterglow detection
  45. GRB 250407A: Swift ToO observations
  46. GRB 250407A: SRG/ART-XC afterglow detection
  47. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  48. IPN triangulation of GRB 250406B (short/hard)
  49. GRB 250331D: Swift-XRT afterglow detection
  50. GRB 250403A: Montarrenti Observatory optical detection
  51. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  52. GRB 250331C Swift-BAT refined analysis
  53. GRB 250331B Swift-BAT refined analysis
  54. GRB 250330A Swift-BAT refined analysis
  55. EP250321A: J band upper limit by SYSU 80cm telescope
  56. GRB 250403A: Swift/UVOT Detection
  57. GRB 250402A: Swift/UVOT Upper Limits
  58. GRB 250403A: LCO optical counterpart detection
  59. GRB 250402A: EP-FXT afterglow detection
  60. GRB 250403A: Swift-XRT observations
  61. GRB 250402A: Swift-XRT observations
  62. GRB 250225B: VLT host galaxy redshift z = 0.950
  63. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  64. GRB 250329B: Swift/UVOT Upper Limit
  65. GRB 250329A: Swift/UVOT Upper Limit
  66. GRB 250327B: Swift/UVOT Detection
  67. GRB 250327A: Swift/UVOT Upper Limits
  68. GRB250331D: AbAO optical observations
  69. GRB 250331D: Fermi GBM observation
  70. GRB 250331C: Swift/UVOT Upper Limits
  71. GRB 250331B: Swift/UVOT Upper Limits
  72. GRB 250331D: Swift-XRT observations
  73. GRB 250331C: Swift-XRT refined Analysis
  74. GRB 250331B: Swift-XRT refined Analysis
  75. GRB 250331B: Swift-XRT refined Analysis
  76. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  77. GRB 250327A Swift-BAT refined analysis
  78. GRB 250329B: CAHA 2.2m telescope optical limit
  79. GRB 250331D: Swift ToO observations
  80. Swift GRB 250331C: Global MASTER-Net observations report
  81. Swift GRB 250331B: Global MASTER-Net observations report
  82. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  83. GRB 250331C: Enhanced Swift-XRT position
  84. GRB 250331B: Enhanced Swift-XRT position
  85. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  86. GRB 250329B: Swift-XRT confirmation of fading
  87. GRB20250327B: 45th Parallel Observatory upper limit
  88. GRB 250328A: Swift/UVOT Detection
  89. GRB 250328A: Swift-XRT refined Analysis
  90. GRB 250330A: Fermi GBM Observation
  91. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  92. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  93. GRB 250331C: Prompt enhanced Swift-XRT position
  94. GRB 250331C: Swift detection of a burst
  95. GRB 250331B: Swift detection of a burst
  96. GRB 250330A: SVOM/VT optical upper limit
  97. GRB 250330A: BOOTES-7 early optical upper limit
  98. GRB 250330A: Swift/UVOT Upper Limits
  99. GRB 250330A: Swift-XRT afterglow detection
  100. GRB 250330A: Fermi GBM Final Localization

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