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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"

25043 results found.

  1. GRB250620C: Fermi GBM Observation
  2. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  3. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  4. Fermi trigger No 772128434: Global MASTER-Net observations report
  5. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  6. GRB 250617B: Nickel telescope optical observations
  7. GRB 250615A: Kilonova-Catcher optical upper limits
  8. GRB 250617B: Assy AZT-20 Optical Observations
  9. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  10. Fermi GRB 250617A: Global MASTER-Net observations report
  11. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  12. GRB 250617B: Swift/UVOT Detection
  13. GRB 250617B: Kilonova-Catcher optical afterglow detection
  14. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  15. GRB 250617B: COLIBRÍ optical observations
  16. GRB 250617B: NOT NIR observations of the afterglow
  17. GRB 250617B: Swift-XRT refined Analysis
  18. GRB 250617B: NUTTelA-TAO early time optical observations
  19. GRB 250617B: Enhanced Swift-XRT position
  20. GRB 250617B: Fermi GBM Observation
  21. GRB 250615A: Swift-BAT refined analysis
  22. GRB 250617B: SAO RAS optical observations
  23. GRB 250617B: Swift detection of a burst with an optical counterpart
  24. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  25. EP#01709178975: Swift-XRT counterpart detection
  26. EP-WXT trigger 01709178975: GOTO optical upper limit
  27. GRB 250615A / EP250615a: AstroSat CZTI detection
  28. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  29. GRB 250615A: COLIBRÍ optical upper limit
  30. GRB 250615A: DDOTI Optical Upper Limit
  31. GRB 250615A: Swift/UVOT Upper Limits
  32. GRB 250615A: Swift-XRT refined Analysis
  33. sb25061207/SVOM: T120 OHP optical upper limit
  34. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  35. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  36. GRB 250615A: Enhanced Swift-XRT position
  37. GRB 250615A: Swift detection of a burst
  38. Fermi trigger No 771718064: Global MASTER-Net observations report
  39. sb25061207: Mephisto optical upper limits
  40. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  41. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  42. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. sb25061218: Swift-XRT observations
  44. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  46. sb25061207: EP-FXT follow-up observation and afterglow candidate
  47. GRB 250612B: Fermi GBM Observation
  48. EP250612a: SVOM/VT optical candidate
  49. GRB 250612C: Fermi GBM Observation
  50. sb25061218: SVOM detection of a X-ray transient
  51. sb25061207: Swift-XRT observations
  52. EP250612a/GRB 250612B: JinShan optical upper limit
  53. sb25061207: SVOM/VT optical counterpart
  54. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  55. GRB 250610B: Swift-XRT refined Analysis
  56. EP250610a: Upper limit from Fermi-GBM Observations
  57. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  58. EP250612a: Einstein Probe detection of an X-ray transient
  59. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  60. sb25061207: SVOM detection of a X-ray transient
  61. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  62. Fermi GBM Sub-Threshold Detection of GRB 250610B
  63. GRB 250610B: Swift/UVOT Detection
  64. EP250610A: Swift/UVOT Upper limits
  65. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  66. EP250610a: TNG NIR upper limit
  67. GRB 250610B: REM optical/NIR observations
  68. EP250610a: Liverpool Telescope optical upper limits
  69. GRB 250610B: additional Liverpool Telescope optical observations
  70. GRB 250610B: SVOM/GRM analysis
  71. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  72. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  73. GRB 250610B: Swift-XRT counterpart detection
  74. GRB 250610B: SVOM/VT optical counterpart
  75. GRB 250610B: OHP/T120 optical counterpart candidate
  76. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  77. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 250605A: Swift-BAT refined analysis
  79. EP250610a: SVOM/VT optical upper limit
  80. EP250610a: REM optical/NIR observations
  81. GRB 250609A: Fermi GBM Observation
  82. EP250610a: Swift-XRT counterpart detection
  83. EP250610a: COLIBRÍ optical upper limit
  84. EP250610a: Einstein Probe detection of an X-ray transient
  85. Fermi trigger No 771072240: Global MASTER-Net observations report
  86. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  87. GRB 250605A: Swift/UVOT Upper Limits
  88. GRB 250527C: CrAO Optical Upper Limit
  89. GRB 250607A: SVOM/GRM observation of a long burst
  90. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  91. GRB 250605A: Swift-XRT refined Analysis
  92. GRB 250605A: Enhanced Swift-XRT position
  93. GRB 250605A: Swift detection of a burst
  94. IPN triangulation of GRB 250404B
  95. IPN triangulation of GRB 250529A
  96. GRB 250601A: PRIME H band upper limit.
  97. GRB 250601A: PRIME J band upper limit.
  98. GRB 250601A: VLT/FORS2 Optical Observation
  99. GRB 250601A: Fermi GBM Observation
  100. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization

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