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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').

18287 results found.

  1. GRB 250403A: LCO optical counterpart detection
  2. GRB 250402A: EP-FXT afterglow detection
  3. GRB 250403A: Swift-XRT observations
  4. GRB 250402A: Swift-XRT observations
  5. GRB 250225B: VLT host galaxy redshift z = 0.950
  6. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  7. GRB 250329B: Swift/UVOT Upper Limit
  8. GRB 250329A: Swift/UVOT Upper Limit
  9. GRB 250327B: Swift/UVOT Detection
  10. GRB 250327A: Swift/UVOT Upper Limits
  11. GRB250331D: AbAO optical observations
  12. GRB 250331D: Fermi GBM observation
  13. GRB 250331C: Swift/UVOT Upper Limits
  14. GRB 250331B: Swift/UVOT Upper Limits
  15. GRB 250331D: Swift-XRT observations
  16. GRB 250331C: Swift-XRT refined Analysis
  17. GRB 250331B: Swift-XRT refined Analysis
  18. GRB 250331B: Swift-XRT refined Analysis
  19. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  20. GRB 250327A Swift-BAT refined analysis
  21. GRB 250329B: CAHA 2.2m telescope optical limit
  22. GRB 250331D: Swift ToO observations
  23. Swift GRB 250331C: Global MASTER-Net observations report
  24. Swift GRB 250331B: Global MASTER-Net observations report
  25. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  26. GRB 250331C: Enhanced Swift-XRT position
  27. GRB 250331B: Enhanced Swift-XRT position
  28. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  29. GRB 250329B: Swift-XRT confirmation of fading
  30. GRB20250327B: 45th Parallel Observatory upper limit
  31. GRB 250328A: Swift/UVOT Detection
  32. GRB 250328A: Swift-XRT refined Analysis
  33. GRB 250330A: Fermi GBM Observation
  34. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  35. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  36. GRB 250331C: Prompt enhanced Swift-XRT position
  37. GRB 250331C: Swift detection of a burst
  38. GRB 250331B: Swift detection of a burst
  39. GRB 250330A: SVOM/VT optical upper limit
  40. GRB 250330A: BOOTES-7 early optical upper limit
  41. GRB 250330A: Swift/UVOT Upper Limits
  42. GRB 250330A: Swift-XRT afterglow detection
  43. GRB 250330A: Fermi GBM Final Localization
  44. GRB 250330A: Prompt Swift-XRT position
  45. GRB 250329B: Swift-XRT afterglow detection
  46. GRB 250330A: Swift detection of a burst
  47. Swift GRB250330.26: Global MASTER-Net observations report
  48. GRB 250329B: SVOM/C-GFT optical upper limit
  49. GRB 250329B: SVOM/VT optical upper limit
  50. GRB 250329A: Swift-XRT afterglow detection
  51. GRB 250328A: SVOM/C-GFT optical upper limit
  52. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  53. GRB 250327B: LCO optical counterpart detection
  54. GRB 250322A: GRANDMA/TNOT optical upper limits
  55. GRB 250327A: SVOM/VT upper limits on the XRT position
  56. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  57. GRB 250327A: Swift-XRT refined Analysis
  58. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  59. GRB 250327A: J-band observations with WINTER
  60. GRB 250327A: SVOM/VT optical candidate
  61. GRB 250327A: Fermi GBM observation
  62. Swift GRB 250327A: Global MASTER-Net observations report
  63. GRB 250327A: DDOTI Optical Observations
  64. GRB 250327A: COLIBRÍ optical upper limit
  65. GRB 250327A: Swift detection of a burst
  66. Konus-Wind detection of GRB 250322A (short)
  67. IPN triangulation of GRB 250322B
  68. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  69. GRB 250322A: Swift-BAT refined analysis
  70. GRB 250322A: Swift/UVOT Upper Limits
  71. GRB 250321B: Swift-XRT observations
  72. GRB 250322A: Swift-XRT refined Analysis
  73. GRB 250322A: AstroSat CZTI detection of a short burst
  74. GRB250322A: STEP/T80S optical limits
  75. GRB 250322A: VLT optical observations
  76. GRB 250322A: VLT near-infrared observations
  77. GRB 250322A: NOT optical upper limits
  78. GRB 250322A: Enhanced Swift-XRT position
  79. GRB 250322A: MASTER optical observation
  80. GRB 250322A: Swift detection of a short burst
  81. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  82. GRB 250225B: GECAM-A detection
  83. GRB 250312A: GECAM-A detection
  84. GRB 250321B: Swift ToO observations
  85. GRB 250321A: Swift-BAT refined analysis
  86. GRB 250321A: Swift-XRT refined Analysis
  87. GRB 250320B: Fermi-LAT detection
  88. GRB 250321A: Swift/UVOT Upper Limits
  89. EP250321a: LCO optical counterpart detection
  90. EP250321a: Swift-XRT detection of an X-ray source
  91. Swift GRB 250321A: Global MASTER-Net observations report
  92. GRB 250321A: GOTO optical upper limits
  93. GRB 250321A: Swift-XRT localisation
  94. GRB 250321A: Fermi GBM Observation
  95. GRB 250321A: Swift detection of a burst
  96. GRB250312A: Swift/UVOT Upper Limits
  97. GRB 250317B: Swift-XRT observations
  98. GRB 250316A: Swift/UVOT Upper Limits
  99. GRB 250314A: REM optical/NIR upper limits
  100. GRB 250316A: AbAO AS-32 Optical Upper Limit

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