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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"

19150 results found.

  1. EP250831a: Swift-XRT observations
  2. GRB 250831A: Swift-XRT counterpart detection
  3. GRB 250830B: Swift-XRT observations
  4. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  5. GRB 250830B: Swift ToO observations
  6. GRB 250830B: MAXI/GSC detection
  7. GRB 250828B: Swift-BAT refined analysis
  8. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  9. Swift GRB 250828B: Global MASTER-Net observations report
  10. EP250827a: Swift/UVOT Detection
  11. GRB 250828B: Swift detection of a burst
  12. EP250827a: confirmation of optical rebrightening with LCO
  13. EP250827a: Swift-XRT counterpart detection
  14. GRB 250823A: Swift-BAT refined analysis
  15. GRB 250823A: Swift-XRT refined Analysis
  16. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  17. GRB 250823A: COLIBRÍ optical observations
  18. GRB 250823A: SVOM/VT optical observation
  19. GRB 250823A: Swift/UVOT Detection
  20. GRB 250823A: NOT optical observations
  21. GRB 250823A: Fermi GBM Observation
  22. GRB 250818B: MeerKAT Detection
  23. GRB 250823A: Enhanced Swift-XRT position
  24. GRB 250823A: LCOGT Optical Detection
  25. GRB 250823A: BOOTES6/DPRT early optical detection
  26. GRB 250823A: Liverpool Telescope optical detection
  27. GRB 250823A: Swift detection of a burst
  28. Swift GRB250823.84: Global MASTER-Net observations report
  29. GRB 250821A: Kilonova-Catcher optical upper limits
  30. EP250821a: Swift/XRT counterpart fading
  31. GRB 250821A: Swift-BAT refined analysis
  32. EP250821a: Swift/UVOT further observations.
  33. GRB 250821A: VLT/FORS2 Optical Observation
  34. GRB 250821A: GECAM-B detection
  35. EP250821a: SVOM/VT optical observation
  36. GRB 250821A: NOT z-band upper limit
  37. GRB 250821A: Swift-XRT refined Analysis
  38. Swift GRB 250821A: Global MASTER-Net observations report
  39. GRB 250821A: Enhanced Swift-XRT position
  40. GRB 250821A: Swift/UVOT Upper Limits
  41. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  42. EP250821a: Swift XRT and UVOT counterpart detection
  43. GRB 250821A: LCOGT Optical Upper Limits
  44. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  45. GRB 250821A: Prompt enhanced Swift-XRT position
  46. GRB 250821A: Swift detection of a burst
  47. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  48. GRB 250814A: Swift/UVOT Upper Limits
  49. GRB 250813B: Swift/UVOT Upper Limit
  50. IPN triangulation of GRB 250814C (short)
  51. IPN triangulation of GRB 250804B (short)
  52. GRB 250818B: Kilonova-Catcher optical afterglow detection
  53. GRB 250818A: AstroSat CZTI detection
  54. GRB 250818B: Swift/UVOT Detection
  55. GRB 250818B: SAO RAS optical observations
  56. Swift GRB 250818A: Global MASTER-Net observations report
  57. GRB 250818A: Swift-XRT refined Analysis
  58. GRB 250818A: Swift-BAT refined analysis
  59. GRB 250818B: Keck redshift of the optical afterglow
  60. GRB 250818A: Swift/UVOT Upper Limits
  61. GRB 250818A: Enhanced Swift-XRT position
  62. GRB 250818A: Fermi GBM Observation
  63. GRB 250818B: SVOM/VT optical observation
  64. GRB 250814A: Further GRAWITA TNG NIR observations
  65. GRB 250818B: Swift-XRT afterglow detection
  66. GRB 250818A: Swift detection of a burst
  67. sb25081602: Swift-XRT observations
  68. GRB 250814A: Swift-BAT refined analysis
  69. GRB 250814A: Further COLIBRÍ optical upper limit
  70. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  71. GRB 250814A: GRAWITA TNG NIR observations
  72. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  73. GRB250814A: TRT optical upper limits
  74. GRB 250814C: SVOM/GRM observation of a short burst
  75. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  76. GRB 250813B: SVOM/GRM observation
  77. GRB 250814A: P200/WIRC observations of the afterglow candidate
  78. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  79. GRB 250814A: KAIT optical upper limit
  80. GRB 250814A: Swift-XRT refined Analysis
  81. GRB 240814A: Fermi GBM Observation
  82. GRB 250814A: Possible afterglow candidate from P200/WIRC
  83. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  84. Swift GRB250814.32: Global MASTER-Net observations report
  85. GRB 250814A: J-band upper limit from WINTER
  86. GRB 250813B: SVOM/VT optical observations
  87. GRB 250814A: COLIBRÍ optical upper limit
  88. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  89. GRB 250814A: DDOTI Optical Upper Limit
  90. GRB 250813B: Swift-XRT afterglow detection
  91. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  92. EP250812a: NOT, NTT, and GS observations
  93. GRB 250812A: Swift/UVOT Detection
  94. EP250812a: SVOM/VT optical counterpart
  95. GRB 250812A: Swift ToO observations
  96. GRB 250807B: Swift-BAT refined analysis
  97. EP 250812a: GOTO optical upper limit
  98. GRB 250812A: Kilonova-Catcher optical afterglow detection
  99. EP250812a: Swift-XRT counterpart detection
  100. GRB 250812A: SVOM/VT optical afterglow confirmation

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