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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').

18308 results found.

  1. EP20250416a: Swift/XRT counterpart detection
  2. GRB 250407A: Mondy and AbAO Optical Observations
  3. IceCube-250406A: Swift-XRT observations
  4. IPN triangulation of GRB 250407A
  5. GRB 250407A: LCO detection of a fading optical counterpart
  6. EP250407a: Swift-XRT observations
  7. Konus-Wind detection of GRB 250407A
  8. GRB 250407A: SVOM/GRM observation of a bright long burst
  9. GRB 250407A: EP-WXT afterglow detection
  10. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  11. GRB 250407A: Fermi GBM Detection
  12. GRB 250407A: Swift-XRT afterglow detection
  13. GRB 250407A: Swift ToO observations
  14. GRB 250407A: SRG/ART-XC afterglow detection
  15. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  16. IPN triangulation of GRB 250406B (short/hard)
  17. GRB 250331D: Swift-XRT afterglow detection
  18. GRB 250403A: Montarrenti Observatory optical detection
  19. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  20. GRB 250331C Swift-BAT refined analysis
  21. GRB 250331B Swift-BAT refined analysis
  22. GRB 250330A Swift-BAT refined analysis
  23. EP250321A: J band upper limit by SYSU 80cm telescope
  24. GRB 250403A: Swift/UVOT Detection
  25. GRB 250402A: Swift/UVOT Upper Limits
  26. GRB 250403A: LCO optical counterpart detection
  27. GRB 250402A: EP-FXT afterglow detection
  28. GRB 250403A: Swift-XRT observations
  29. GRB 250402A: Swift-XRT observations
  30. GRB 250225B: VLT host galaxy redshift z = 0.950
  31. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  32. GRB 250329B: Swift/UVOT Upper Limit
  33. GRB 250329A: Swift/UVOT Upper Limit
  34. GRB 250327B: Swift/UVOT Detection
  35. GRB 250327A: Swift/UVOT Upper Limits
  36. GRB250331D: AbAO optical observations
  37. GRB 250331D: Fermi GBM observation
  38. GRB 250331C: Swift/UVOT Upper Limits
  39. GRB 250331B: Swift/UVOT Upper Limits
  40. GRB 250331D: Swift-XRT observations
  41. GRB 250331C: Swift-XRT refined Analysis
  42. GRB 250331B: Swift-XRT refined Analysis
  43. GRB 250331B: Swift-XRT refined Analysis
  44. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  45. GRB 250327A Swift-BAT refined analysis
  46. GRB 250329B: CAHA 2.2m telescope optical limit
  47. GRB 250331D: Swift ToO observations
  48. Swift GRB 250331C: Global MASTER-Net observations report
  49. Swift GRB 250331B: Global MASTER-Net observations report
  50. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  51. GRB 250331C: Enhanced Swift-XRT position
  52. GRB 250331B: Enhanced Swift-XRT position
  53. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  54. GRB 250329B: Swift-XRT confirmation of fading
  55. GRB20250327B: 45th Parallel Observatory upper limit
  56. GRB 250328A: Swift/UVOT Detection
  57. GRB 250328A: Swift-XRT refined Analysis
  58. GRB 250330A: Fermi GBM Observation
  59. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  60. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  61. GRB 250331C: Prompt enhanced Swift-XRT position
  62. GRB 250331C: Swift detection of a burst
  63. GRB 250331B: Swift detection of a burst
  64. GRB 250330A: SVOM/VT optical upper limit
  65. GRB 250330A: BOOTES-7 early optical upper limit
  66. GRB 250330A: Swift/UVOT Upper Limits
  67. GRB 250330A: Swift-XRT afterglow detection
  68. GRB 250330A: Fermi GBM Final Localization
  69. GRB 250330A: Prompt Swift-XRT position
  70. GRB 250329B: Swift-XRT afterglow detection
  71. GRB 250330A: Swift detection of a burst
  72. Swift GRB250330.26: Global MASTER-Net observations report
  73. GRB 250329B: SVOM/C-GFT optical upper limit
  74. GRB 250329B: SVOM/VT optical upper limit
  75. GRB 250329A: Swift-XRT afterglow detection
  76. GRB 250328A: SVOM/C-GFT optical upper limit
  77. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  78. GRB 250327B: LCO optical counterpart detection
  79. GRB 250322A: GRANDMA/TNOT optical upper limits
  80. GRB 250327A: SVOM/VT upper limits on the XRT position
  81. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  82. GRB 250327A: Swift-XRT refined Analysis
  83. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  84. GRB 250327A: J-band observations with WINTER
  85. GRB 250327A: SVOM/VT optical candidate
  86. GRB 250327A: Fermi GBM observation
  87. Swift GRB 250327A: Global MASTER-Net observations report
  88. GRB 250327A: DDOTI Optical Observations
  89. GRB 250327A: COLIBRÍ optical upper limit
  90. GRB 250327A: Swift detection of a burst
  91. Konus-Wind detection of GRB 250322A (short)
  92. IPN triangulation of GRB 250322B
  93. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  94. GRB 250322A: Swift-BAT refined analysis
  95. GRB 250322A: Swift/UVOT Upper Limits
  96. GRB 250321B: Swift-XRT observations
  97. GRB 250322A: Swift-XRT refined Analysis
  98. GRB 250322A: AstroSat CZTI detection of a short burst
  99. GRB250322A: STEP/T80S optical limits
  100. GRB 250322A: VLT optical observations

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