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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"

18144 results found.

  1. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  2. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  3. GRB 250617B: Nickel telescope optical observations
  4. GRB 250615A: Kilonova-Catcher optical upper limits
  5. GRB 250617B: Assy AZT-20 Optical Observations
  6. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  7. GRB 250617B: Swift/UVOT Detection
  8. GRB 250617B: Kilonova-Catcher optical afterglow detection
  9. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  10. GRB 250617B: COLIBRÍ optical observations
  11. GRB 250617B: NOT NIR observations of the afterglow
  12. GRB 250617B: NUTTelA-TAO early time optical observations
  13. GRB 250617B: Enhanced Swift-XRT position
  14. The EP-WXT trigger 01709178990 is likely a flaring star
  15. GRB 250617B: SAO RAS optical observations
  16. GRB 250617B: Swift detection of a burst with an optical counterpart
  17. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  18. EP-WXT trigger 01709178975: GOTO optical upper limit
  19. GRB 250615A / EP250615a: AstroSat CZTI detection
  20. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  21. GRB 250615A: COLIBRÍ optical upper limit
  22. GRB 250615A: DDOTI Optical Upper Limit
  23. GRB 250615A: Swift/UVOT Upper Limits
  24. sb25061207/SVOM: T120 OHP optical upper limit
  25. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  26. GRB 250615A: Enhanced Swift-XRT position
  27. GRB 250615A: Swift detection of a burst
  28. sb25061207: Mephisto optical upper limits
  29. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  30. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  31. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  33. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  34. sb25061207: EP-FXT follow-up observation and afterglow candidate
  35. EP250612a: SVOM/VT optical candidate
  36. sb25061218: SVOM detection of a X-ray transient
  37. EP250612a/GRB 250612B: JinShan optical upper limit
  38. sb25061207: SVOM/VT optical counterpart
  39. GRB 250610B: Swift-XRT refined Analysis
  40. EP250612a: Einstein Probe detection of an X-ray transient
  41. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  42. sb25061207: SVOM detection of a X-ray transient
  43. GRB 250610B: Swift/UVOT Detection
  44. EP250610A: Swift/UVOT Upper limits
  45. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  46. EP250610a: TNG NIR upper limit
  47. GRB 250610B: REM optical/NIR observations
  48. EP250610a: Liverpool Telescope optical upper limits
  49. GRB 250610B: additional Liverpool Telescope optical observations
  50. GRB 250610B: SVOM/VT optical counterpart
  51. GRB 250610B: OHP/T120 optical counterpart candidate
  52. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  53. GRB 250610B: SVOM detection of a long burst
  54. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  55. EP250610a: SVOM/VT optical upper limit
  56. EP250610a: REM optical/NIR observations
  57. EP250610a: COLIBRÍ optical upper limit
  58. EP250610a: Einstein Probe detection of an X-ray transient
  59. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  60. GRB 250605A: Swift/UVOT Upper Limits
  61. GRB 250527C: CrAO Optical Upper Limit
  62. GRB 250607A: SVOM/GRM observation of a long burst
  63. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  64. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  65. The EP-WXT trigger 01709178069 is likely a flaring star
  66. GRB 250605A: Enhanced Swift-XRT position
  67. Fermi trigger No 770867684: Global MASTER-Net observations report
  68. GRB 250605A: Swift detection of a burst
  69. IPN triangulation of GRB 250404B
  70. IPN triangulation of GRB 250529A
  71. GRB 250601A: PRIME H band upper limit.
  72. GRB 250601A: PRIME J band upper limit.
  73. GRB 250601A: VLT/FORS2 Optical Observation
  74. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  75. GRB 250603A: Swift/UVOT Upper Limits
  76. GRB 250603A: Enhanced Swift-XRT position
  77. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  78. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  79. GRB 250602A: DDOTI Optical Upper Limit
  80. GRB 250601A: Swift ToO observations
  81. EP#01709177494: SVOM/VT optical observations
  82. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  83. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  84. GRB 250530C: Enhanced Swift-XRT position
  85. GRB 250530C: Swift detection of a burst
  86. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  87. GRB 250530A: SVOM/VT optical upper limit
  88. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  89. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  90. GRB 250530A: SVOM detection of a burst
  91. GRB 250527C: Swift/UVOT Upper Limits
  92. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  93. GRB 250527B: Swift-XRT observations
  94. GRB 250527C: Swift ToO observations
  95. GRB 250527B: Tiled Swift observations
  96. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  97. EP250526a: COLIBRÍ optical upper limits
  98. EP250526a: Einstein Probe detection of a fast X-ray transient
  99. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  100. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation

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