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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"

19416 results found.

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

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