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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28198 results found.

  1. IPN triangulation of GRB 250804B (short)
  2. GRB 250818B: Kilonova-Catcher optical afterglow detection
  3. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  4. GRB 250818B: Liverpool Telescope optical detections
  5. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  6. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  7. GRB 250818A: AstroSat CZTI detection
  8. GRB 250818B: Swift/UVOT Detection
  9. GRB 250820A: Fermi GBM Final Real-time Localization
  10. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  11. GRB 250818B: TRT Optical Observation
  12. GRB 250818B: SAO RAS optical observations
  13. GRB 250818B: NOT optical observations
  14. GRB 250818A: Swift-XRT refined Analysis
  15. GRB 250818B: EP-FXT counterpart detection
  16. GRB 250818C: Fermi GBM Final Real-time Localization
  17. GRB 250818B: Keck redshift of the optical afterglow
  18. GRB 250818B: KAIT optical observations
  19. GRB 250818A: Swift/UVOT Upper Limits
  20. GRB 250818A: Enhanced Swift-XRT position
  21. GRB 250818B: SVOM/VT optical observation
  22. GRB 250814A: Further GRAWITA TNG NIR observations
  23. GRB 250818B: Swift-XRT afterglow detection
  24. GRB 250818B: SVOM detection of a short burst
  25. GRB 250818A: Swift detection of a burst
  26. GRB 250818A: Fermi GBM Final Real-time Localization
  27. sb25081602: Swift-XRT observations
  28. SVOM/sb25081602: detection of a likely X-ray transient
  29. GRB 250816A: Fermi GBM Final Real-time Localization
  30. GRB 250815A: Fermi GBM Final Localization
  31. GRB 250813B: Liverpool Telescope optical upper limits
  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 250812A: SVOM/VT optical continued observation
  36. GRB250814A: TRT optical upper limits
  37. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  38. GRB 250813B: SVOM/GRM observation
  39. GRB 250814A: P200/WIRC observations of the afterglow candidate
  40. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  41. GRB 250814A: KAIT optical upper limit
  42. GRB 250814A: Swift-XRT refined Analysis
  43. GRB 250814A: Possible afterglow candidate from P200/WIRC
  44. GRB 250813B: Fermi GBM Observation
  45. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  46. GRB 250814A: J-band upper limit from WINTER
  47. GRB 250813B: NOT observations of the optical afterglow
  48. GRB 250813B: SVOM/VT optical observations
  49. Subject GRB 250813B: SVOM/MXT refined analysis
  50. GRB 250814A: COLIBRÍ optical upper limit
  51. GRB 250814B: Fermi GBM Final Real-time Localization
  52. GRB 250813A: AstroSat CZTI detection
  53. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  54. GRB 250814A: DDOTI Optical Upper Limit
  55. GRB 250813B: EP-FXT counterpart detection
  56. GRB 250813B: Swift-XRT afterglow detection
  57. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  58. GRB 250814A: Fermi GBM Final Real-time Localization
  59. GRB 250813B: Ondrejov D50 fast decay
  60. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  61. GRB 250813B: Ondrejov D50 optical afterglow detection
  62. GRB 250813B: SVOM detection of a bright long burst
  63. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  64. GRB 250812A: NTT spectroscopic redshift z = 2.57
  65. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  66. EP250812a: NOT, NTT, and GS observations
  67. GRB 250812A: Swift/UVOT Detection
  68. GRB 250813A: Fermi GBM Final Localization
  69. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  70. EP250812a: Liverpool Telescope upper limits
  71. EP250812a: SVOM/VT optical counterpart
  72. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 250812A: EP-FXT counterpart detection
  74. GRB 250812A: Swift ToO observations
  75. EP 250812a: GOTO optical upper limit
  76. GRB 250812A: Kilonova-Catcher optical afterglow detection
  77. EP250812a: Swift-XRT counterpart detection
  78. EP250812a: Einstein Probe detection of an X-ray transient
  79. GRB 250812A: SVOM/VT optical afterglow confirmation
  80. GRB 250812A: Swift-XRT afterglow detection
  81. GRB 250812A: TRT likely optical counterpart detection
  82. GRB 250812A: SVOM detection of a faint long burst
  83. GRB 250809A: Swift/UVOT Detection
  84. Corrected Swift-XRT Refined Analysis of GRB 250809A
  85. GRB 250809A: Swift-XRT refined Analysis
  86. GRB 250809A: LCOGT Optical Upper Limits
  87. GRB 250702B: Chandra X-ray Detection
  88. GRB 250808A: VLT X-shooter candidate counterpart
  89. GRB 250809A: Prompt enhanced Swift-XRT position
  90. GRB 250809A: Swift detection of a gamma ray burst
  91. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. GRB 250808A: Swift-XRT candidate counterpart detection
  93. GRB 250807A: SVOM/VT optical continued observation
  94. GRB 250808A: SVOM detection of a long burst
  95. GRB 250808A: Fermi GBM Final Real-time Localization
  96. Konus-Wind detection of GRB 250807A
  97. GRB 250807B: Swift/UVOT Detection
  98. GRB 250807B: Kilonova-Catcher optical afterglow detection
  99. GRB 250807A: Swift/UVOT Detection
  100. GRB 250807A: Swift-XRT refined Analysis

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