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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"

19128 results found.

  1. GRB 250823A: Swift/UVOT Detection
  2. GRB 250823A: NOT optical observations
  3. GRB 250823A: Fermi GBM Observation
  4. GRB 250818B: MeerKAT Detection
  5. GRB 250823A: Enhanced Swift-XRT position
  6. GRB 250823A: LCOGT Optical Detection
  7. GRB 250823A: BOOTES6/DPRT early optical detection
  8. GRB 250823A: Liverpool Telescope optical detection
  9. GRB 250823A: Swift detection of a burst
  10. Swift GRB250823.84: Global MASTER-Net observations report
  11. GRB 250821A: Kilonova-Catcher optical upper limits
  12. EP250821a: Swift/XRT counterpart fading
  13. GRB 250821A: Swift-BAT refined analysis
  14. EP250821a: Swift/UVOT further observations.
  15. GRB 250821A: VLT/FORS2 Optical Observation
  16. GRB 250821A: GECAM-B detection
  17. EP250821a: SVOM/VT optical observation
  18. GRB 250821A: NOT z-band upper limit
  19. GRB 250821A: Swift-XRT refined Analysis
  20. Swift GRB 250821A: Global MASTER-Net observations report
  21. GRB 250821A: Enhanced Swift-XRT position
  22. GRB 250821A: Swift/UVOT Upper Limits
  23. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  24. EP250821a: Swift XRT and UVOT counterpart detection
  25. GRB 250821A: LCOGT Optical Upper Limits
  26. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  27. GRB 250821A: Prompt enhanced Swift-XRT position
  28. GRB 250821A: Swift detection of a burst
  29. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  30. GRB 250814A: Swift/UVOT Upper Limits
  31. GRB 250813B: Swift/UVOT Upper Limit
  32. IPN triangulation of GRB 250814C (short)
  33. IPN triangulation of GRB 250804B (short)
  34. GRB 250818B: Kilonova-Catcher optical afterglow detection
  35. GRB 250818A: AstroSat CZTI detection
  36. GRB 250818B: Swift/UVOT Detection
  37. GRB 250818B: SAO RAS optical observations
  38. Swift GRB 250818A: Global MASTER-Net observations report
  39. GRB 250818A: Swift-XRT refined Analysis
  40. GRB 250818A: Swift-BAT refined analysis
  41. GRB 250818B: Keck redshift of the optical afterglow
  42. GRB 250818A: Swift/UVOT Upper Limits
  43. GRB 250818A: Enhanced Swift-XRT position
  44. GRB 250818A: Fermi GBM Observation
  45. GRB 250818B: SVOM/VT optical observation
  46. GRB 250814A: Further GRAWITA TNG NIR observations
  47. GRB 250818B: Swift-XRT afterglow detection
  48. GRB 250818A: Swift detection of a burst
  49. sb25081602: Swift-XRT observations
  50. GRB 250814A: Swift-BAT refined analysis
  51. GRB 250814A: Further COLIBRÍ optical upper limit
  52. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  53. GRB 250814A: GRAWITA TNG NIR observations
  54. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  55. GRB250814A: TRT optical upper limits
  56. GRB 250814C: SVOM/GRM observation of a short burst
  57. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  58. GRB 250813B: SVOM/GRM observation
  59. GRB 250814A: P200/WIRC observations of the afterglow candidate
  60. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  61. GRB 250814A: KAIT optical upper limit
  62. GRB 250814A: Swift-XRT refined Analysis
  63. GRB 240814A: Fermi GBM Observation
  64. GRB 250814A: Possible afterglow candidate from P200/WIRC
  65. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  66. Swift GRB250814.32: Global MASTER-Net observations report
  67. GRB 250814A: J-band upper limit from WINTER
  68. GRB 250813B: SVOM/VT optical observations
  69. GRB 250814A: COLIBRÍ optical upper limit
  70. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  71. GRB 250814A: DDOTI Optical Upper Limit
  72. GRB 250813B: Swift-XRT afterglow detection
  73. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  74. EP250812a: NOT, NTT, and GS observations
  75. GRB 250812A: Swift/UVOT Detection
  76. EP250812a: SVOM/VT optical counterpart
  77. GRB 250812A: Swift ToO observations
  78. GRB 250807B: Swift-BAT refined analysis
  79. EP 250812a: GOTO optical upper limit
  80. GRB 250812A: Kilonova-Catcher optical afterglow detection
  81. EP250812a: Swift-XRT counterpart detection
  82. GRB 250812A: SVOM/VT optical afterglow confirmation
  83. GRB 250812A: Swift-XRT afterglow detection
  84. GRB 250809A: Swift-BAT refined analysis
  85. GRB 250807A: Swift-BAT refined analysis
  86. GRB 250809A: Swift/UVOT Detection
  87. Corrected Swift-XRT Refined Analysis of GRB 250809A
  88. GRB 250809A: Swift-XRT refined Analysis
  89. GRB 250807B: SVOM/VT optical observation
  90. GRB 250809A: LCOGT Optical Upper Limits
  91. GRB 250702B: Chandra X-ray Detection
  92. GRB 250808A: VLT X-shooter candidate counterpart
  93. GRB 250809A: Prompt enhanced Swift-XRT position
  94. GRB 250809A: Swift detection of a gamma ray burst
  95. GRB 250808A: Swift-XRT candidate counterpart detection
  96. GRB 250807A: SVOM/VT optical continued observation
  97. Konus-Wind detection of GRB 250807A
  98. GRB 250807B: Swift/UVOT Detection
  99. GRB 250807B: Kilonova-Catcher optical afterglow detection
  100. GRB 250807A: Swift/UVOT Detection

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