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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"

19609 results found.

  1. EP250407a: Swift-XRT observations
  2. Konus-Wind detection of GRB 250407A
  3. GRB 250407A: SVOM/GRM observation of a bright long burst
  4. GRB 250407A: EP-WXT afterglow detection
  5. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  6. GRB 250407A: Fermi GBM Detection
  7. GRB 250407A: Swift-XRT afterglow detection
  8. GRB 250407A: Swift ToO observations
  9. GRB 250407A: SRG/ART-XC afterglow detection
  10. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  11. IPN triangulation of GRB 250406B (short/hard)
  12. GRB 250331D: Swift-XRT afterglow detection
  13. GRB 250403A: Montarrenti Observatory optical detection
  14. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  15. GRB 250331C Swift-BAT refined analysis
  16. GRB 250331B Swift-BAT refined analysis
  17. GRB 250330A Swift-BAT refined analysis
  18. EP250321A: J band upper limit by SYSU 80cm telescope
  19. GRB 250403A: Swift/UVOT Detection
  20. GRB 250402A: Swift/UVOT Upper Limits
  21. GRB 250403A: LCO optical counterpart detection
  22. GRB 250402A: EP-FXT afterglow detection
  23. GRB 250403A: Swift-XRT observations
  24. GRB 250402A: Swift-XRT observations
  25. GRB 250225B: VLT host galaxy redshift z = 0.950
  26. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  27. GRB 250329B: Swift/UVOT Upper Limit
  28. GRB 250329A: Swift/UVOT Upper Limit
  29. GRB 250327B: Swift/UVOT Detection
  30. GRB 250327A: Swift/UVOT Upper Limits
  31. GRB250331D: AbAO optical observations
  32. GRB 250331D: Fermi GBM observation
  33. GRB 250331C: Swift/UVOT Upper Limits
  34. GRB 250331B: Swift/UVOT Upper Limits
  35. GRB 250331D: Swift-XRT observations
  36. GRB 250331C: Swift-XRT refined Analysis
  37. GRB 250331B: Swift-XRT refined Analysis
  38. GRB 250331B: Swift-XRT refined Analysis
  39. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  40. GRB 250327A Swift-BAT refined analysis
  41. GRB 250329B: CAHA 2.2m telescope optical limit
  42. GRB 250331D: Swift ToO observations
  43. Swift GRB 250331C: Global MASTER-Net observations report
  44. Swift GRB 250331B: Global MASTER-Net observations report
  45. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  46. GRB 250331C: Enhanced Swift-XRT position
  47. GRB 250331B: Enhanced Swift-XRT position
  48. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  49. GRB 250329B: Swift-XRT confirmation of fading
  50. GRB20250327B: 45th Parallel Observatory upper limit
  51. GRB 250328A: Swift/UVOT Detection
  52. GRB 250328A: Swift-XRT refined Analysis
  53. GRB 250330A: Fermi GBM Observation
  54. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  55. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  56. GRB 250331C: Prompt enhanced Swift-XRT position
  57. GRB 250331C: Swift detection of a burst
  58. GRB 250331B: Swift detection of a burst
  59. GRB 250330A: SVOM/VT optical upper limit
  60. GRB 250330A: BOOTES-7 early optical upper limit
  61. GRB 250330A: Swift/UVOT Upper Limits
  62. GRB 250330A: Swift-XRT afterglow detection
  63. GRB 250330A: Fermi GBM Final Localization
  64. GRB 250330A: Prompt Swift-XRT position
  65. GRB 250329B: Swift-XRT afterglow detection
  66. GRB 250330A: Swift detection of a burst
  67. Swift GRB250330.26: Global MASTER-Net observations report
  68. GRB 250329B: SVOM/C-GFT optical upper limit
  69. GRB 250329B: SVOM/VT optical upper limit
  70. GRB 250329A: Swift-XRT afterglow detection
  71. GRB 250328A: SVOM/C-GFT optical upper limit
  72. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  73. GRB 250327B: LCO optical counterpart detection
  74. GRB 250322A: GRANDMA/TNOT optical upper limits
  75. GRB 250327A: SVOM/VT upper limits on the XRT position
  76. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  77. GRB 250327A: Swift-XRT refined Analysis
  78. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  79. GRB 250327A: J-band observations with WINTER
  80. GRB 250327A: SVOM/VT optical candidate
  81. GRB 250327A: Fermi GBM observation
  82. Swift GRB 250327A: Global MASTER-Net observations report
  83. GRB 250327A: DDOTI Optical Observations
  84. GRB 250327A: COLIBRÍ optical upper limit
  85. GRB 250327A: Swift detection of a burst
  86. Konus-Wind detection of GRB 250322A (short)
  87. IPN triangulation of GRB 250322B
  88. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  89. GRB 250322A: Swift-BAT refined analysis
  90. GRB 250322A: Swift/UVOT Upper Limits
  91. GRB 250321B: Swift-XRT observations
  92. GRB 250322A: Swift-XRT refined Analysis
  93. GRB 250322A: AstroSat CZTI detection of a short burst
  94. GRB250322A: STEP/T80S optical limits
  95. GRB 250322A: VLT optical observations
  96. GRB 250322A: VLT near-infrared observations
  97. GRB 250322A: NOT optical upper limits
  98. GRB 250322A: Enhanced Swift-XRT position
  99. GRB 250322A: MASTER optical observation
  100. GRB 250322A: Swift detection of a short burst

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