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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"

21393 results found.

  1. GRB 250331D: Swift-XRT observations
  2. GRB 250331C: Swift-XRT refined Analysis
  3. GRB 250331B: Swift-XRT refined Analysis
  4. GRB 250331B: Swift-XRT refined Analysis
  5. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  6. GRB 250327A Swift-BAT refined analysis
  7. GRB 250329B: CAHA 2.2m telescope optical limit
  8. GRB 250331D: Swift ToO observations
  9. Swift GRB 250331C: Global MASTER-Net observations report
  10. Swift GRB 250331B: Global MASTER-Net observations report
  11. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  12. GRB 250331C: Enhanced Swift-XRT position
  13. GRB 250331B: Enhanced Swift-XRT position
  14. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  15. GRB 250329B: Swift-XRT confirmation of fading
  16. GRB 250330A: VLT/FORS2 Afterglow Detection
  17. GRB20250327B: 45th Parallel Observatory upper limit
  18. GRB 250328A: Swift/UVOT Detection
  19. GRB 250328A: Swift-XRT refined Analysis
  20. GRB 250330A: Fermi GBM Observation
  21. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  22. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  23. GRB 250331C: Prompt enhanced Swift-XRT position
  24. GRB 250331C: Swift detection of a burst
  25. GRB 250331B: Swift detection of a burst
  26. GRB 250330A: SVOM/VT optical upper limit
  27. GRB 250330A: BOOTES-7 early optical upper limit
  28. GRB 250330A: Swift/UVOT Upper Limits
  29. GRB 250330A: Swift-XRT afterglow detection
  30. GRB 250328A: 1.6m Mephisto optical observations
  31. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  32. GRB 250330A: Fermi GBM Final Localization
  33. GRB 250330A: VLT/FORS2 Optical Observations
  34. GRB 250330A: Prompt Swift-XRT position
  35. GRB 250329B: Swift-XRT afterglow detection
  36. GRB 250330A: Swift detection of a burst
  37. Swift GRB250330.26: Global MASTER-Net observations report
  38. GRB 250329B: SVOM/C-GFT optical upper limit
  39. GRB 250329B: SVOM/VT optical upper limit
  40. GRB 250329A: Swift-XRT afterglow detection
  41. GRB 250328A: SVOM/C-GFT optical upper limit
  42. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  43. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  44. GRB 250327B: LCO optical counterpart detection
  45. GRB 250322A: GRANDMA/TNOT optical upper limits
  46. GRB 250327A: SVOM/VT upper limits on the XRT position
  47. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  48. GRB 250327A: Swift-XRT refined Analysis
  49. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  50. GRB 250327A: J-band observations with WINTER
  51. GRB 250327A: SVOM/VT optical candidate
  52. GRB 250327A: Fermi GBM observation
  53. Swift GRB 250327A: Global MASTER-Net observations report
  54. GRB 250327A: DDOTI Optical Observations
  55. GRB 250327A: COLIBRÍ optical upper limit
  56. GRB 250327A: Swift detection of a burst
  57. Konus-Wind detection of GRB 250322A (short)
  58. IPN triangulation of GRB 250322B
  59. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  60. GRB 250322A: Swift-BAT refined analysis
  61. GRB 250322A: further NOT optical observations
  62. GRB 250322A: Swift/UVOT Upper Limits
  63. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  64. GRB 250321B: Swift-XRT observations
  65. GRB 250322A: Swift-XRT refined Analysis
  66. GRB 250322A: Gemini-North redshift of candidate host galaxy
  67. GRB 250322A: AstroSat CZTI detection of a short burst
  68. GRB250322A: STEP/T80S optical limits
  69. GRB 250322A: Gemini-South optical observations
  70. GRB 250322A: VLT optical observations
  71. GRB 250322A: VLT near-infrared observations
  72. GRB 250322A: NOT optical upper limits
  73. GRB 250322A: Enhanced Swift-XRT position
  74. GRB 250322A: MASTER optical observation
  75. GRB 250322A: Swift detection of a short burst
  76. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 250225B: GECAM-A detection
  78. GRB 250312A: GECAM-A detection
  79. GRB 250321B: Swift ToO observations
  80. GRB 250321A: Swift-BAT refined analysis
  81. GRB 250321A: Swift-XRT refined Analysis
  82. GRB 250320B: Fermi-LAT detection
  83. GRB 250321A: Swift/UVOT Upper Limits
  84. EP250321a: LCO optical counterpart detection
  85. EP250321a: Swift-XRT detection of an X-ray source
  86. Swift GRB 250321A: Global MASTER-Net observations report
  87. GRB 250321A: GOTO optical upper limits
  88. GRB 250321A: Swift-XRT localisation
  89. GRB 250321A: Fermi GBM Observation
  90. GRB 250321A: Swift detection of a burst
  91. GRB250312A: Swift/UVOT Upper Limits
  92. GRB 250317B: Swift-XRT observations
  93. GRB 250316A: Swift/UVOT Upper Limits
  94. GRB 250314A: REM optical/NIR upper limits
  95. GRB 250316A: AbAO AS-32 Optical Upper Limit
  96. GRB 250316A: Swift-XRT afterglow detection
  97. GRB 250316A: Fermi GBM Observation
  98. GRB 250316A: Swift-XRT observations
  99. GRB 250316A: Swift ToO observations
  100. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst

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