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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"

19949 results found.

  1. GRB 250821A: Enhanced Swift-XRT position
  2. GRB 250821A: Swift/UVOT Upper Limits
  3. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  4. EP250821a: Swift XRT and UVOT counterpart detection
  5. GRB 250821A: LCOGT Optical Upper Limits
  6. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  7. GRB 250821A: Prompt enhanced Swift-XRT position
  8. GRB 250821A: Swift detection of a burst
  9. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  10. GRB 250814A: Swift/UVOT Upper Limits
  11. GRB 250813B: Swift/UVOT Upper Limit
  12. IPN triangulation of GRB 250814C (short)
  13. IPN triangulation of GRB 250804B (short)
  14. GRB 250818B: Kilonova-Catcher optical afterglow detection
  15. GRB 250818A: AstroSat CZTI detection
  16. GRB 250818B: Swift/UVOT Detection
  17. GRB 250818B: SAO RAS optical observations
  18. Swift GRB 250818A: Global MASTER-Net observations report
  19. GRB 250818A: Swift-XRT refined Analysis
  20. GRB 250818A: Swift-BAT refined analysis
  21. GRB 250818B: Keck redshift of the optical afterglow
  22. GRB 250818A: Swift/UVOT Upper Limits
  23. GRB 250818A: Enhanced Swift-XRT position
  24. GRB 250818A: Fermi GBM Observation
  25. GRB 250818B: SVOM/VT optical observation
  26. GRB 250814A: Further GRAWITA TNG NIR observations
  27. GRB 250818B: Swift-XRT afterglow detection
  28. GRB 250818A: Swift detection of a burst
  29. sb25081602: Swift-XRT observations
  30. GRB 250814A: Swift-BAT refined analysis
  31. GRB 250815A: Fermi GBM Final Localization
  32. GRB 250814A: Further COLIBRÍ optical upper limit
  33. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  34. GRB 250814A: GRAWITA TNG NIR observations
  35. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  36. GRB250814A: TRT optical upper limits
  37. GRB 250814C: SVOM/GRM observation of a short burst
  38. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  39. GRB 250813B: SVOM/GRM observation
  40. GRB 250814A: P200/WIRC observations of the afterglow candidate
  41. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  42. GRB 250814A: KAIT optical upper limit
  43. GRB 250814A: Swift-XRT refined Analysis
  44. GRB 240814A: Fermi GBM Observation
  45. GRB 250814A: Possible afterglow candidate from P200/WIRC
  46. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  47. Swift GRB250814.32: Global MASTER-Net observations report
  48. GRB 250814A: J-band upper limit from WINTER
  49. GRB 250813B: SVOM/VT optical observations
  50. GRB 250814A: COLIBRÍ optical upper limit
  51. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  52. GRB 250814A: DDOTI Optical Upper Limit
  53. GRB 250813B: Swift-XRT afterglow detection
  54. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  55. EP250812a: NOT, NTT, and GS observations
  56. GRB 250812A: Swift/UVOT Detection
  57. EP250812a: SVOM/VT optical counterpart
  58. GRB 250812A: Swift ToO observations
  59. GRB 250807B: Swift-BAT refined analysis
  60. EP 250812a: GOTO optical upper limit
  61. GRB 250812A: Kilonova-Catcher optical afterglow detection
  62. EP250812a: Swift-XRT counterpart detection
  63. GRB 250812A: SVOM/VT optical afterglow confirmation
  64. GRB 250812A: Swift-XRT afterglow detection
  65. GRB 250809A: Swift-BAT refined analysis
  66. GRB 250807A: Swift-BAT refined analysis
  67. GRB 250809A: Swift/UVOT Detection
  68. Corrected Swift-XRT Refined Analysis of GRB 250809A
  69. GRB 250809A: Swift-XRT refined Analysis
  70. GRB 250807B: SVOM/VT optical observation
  71. GRB 250809A: LCOGT Optical Upper Limits
  72. GRB 250702B: Chandra X-ray Detection
  73. GRB 250808A: VLT X-shooter candidate counterpart
  74. GRB 250809A: Prompt enhanced Swift-XRT position
  75. GRB 250809A: Swift detection of a gamma ray burst
  76. GRB 250808A: Swift-XRT candidate counterpart detection
  77. GRB 250807A: SVOM/VT optical continued observation
  78. Konus-Wind detection of GRB 250807A
  79. GRB 250807B: Swift/UVOT Detection
  80. GRB 250807B: Kilonova-Catcher optical afterglow detection
  81. GRB 250807A: Swift/UVOT Detection
  82. GRB 250807A: Swift-XRT refined Analysis
  83. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  84. GRB 250806A: SVOM/MXT refined analysis
  85. GRB 250806A: SVOM/ECLAIRs refined analysis
  86. GRB 250807A: SVOM/GRM observation
  87. Swift GRB250807.45: Global MASTER-Net observations report
  88. GRB 250807A: AstroSat CZTI detection of bright long burst
  89. GRB 250807B: Swift-XRT refined Analysis
  90. GRB 250807B: NTT optical observations
  91. GRB 250807A: SVOM/VT optical observation
  92. GRB 250807B: Enhanced Swift-XRT position
  93. Swift GRB250807.65: Global MASTER-Net observations report
  94. GRB 250807A: Enhanced Swift-XRT position
  95. GRB 250807B: Swift detection of a burst with an optical counterpart.
  96. GRB 250805A: Kilonova-Catcher optical upper limits
  97. GRB 250805A: Swift/UVOT Upper Limits
  98. GRB 250806A: Swift/UVOT U-band detection
  99. GRB 250807A: Swift detection of a burst with an optical counterpart
  100. GRB 250806A: EP-FXT observation

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