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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"

28101 results found.

  1. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  2. EP250702a: WFST optical observations
  3. EP250704a: Einstein Probe detection of an X-ray transient
  4. GRB 250702F: optical photometry from Konkoly
  5. GRB 250704A: REM detection of the optical afterglow
  6. GRB 250702F: SVOM/VT optical observation
  7. GRB 250704A: SVOM detection of a burst
  8. GRB 250702F: Swift/UVOT Detection
  9. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  10. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  11. GRB 250702F: Swift-XRT refined Analysis
  12. GRB 250702F: Leavitt Observatory optical observations
  13. GRB 250702F: AKO Optical Afterglow Detection
  14. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  15. GRB 250702A: GECAM-B detection
  16. GRB 250702F: Skynet Optical Observations
  17. GRB 250424A: VIRT Optical Upper Limit
  18. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  19. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  20. GRB 250702F: TRT Optical Observation
  21. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  22. GRB 250702F: REM optical afterglow detection
  23. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  24. GRB 250703A: Fermi GBM Final Real-time Localization
  25. GRB 250702F: COLIBRÍ Observations of the Afterglow
  26. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  27. GRB 250702F: Enhanced Swift-XRT position
  28. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  29. GRB 250702F: NOT observations of the optical afterglow
  30. GRB 250702F: MASTER optical afterglow observation
  31. GRB 250702F: GOTO optical counterpart detection
  32. GRB 250702F: Ondrejov D50 optical afterglow detection
  33. GRB 250702F: Swift detection of a burst with an optical counterpart
  34. GRB 250702F: Fermi GBM Final Real-time Localization
  35. GRB 250702E: Fermi GBM Final Real-time Localization
  36. Konus-Wind detection of GRB 250627A
  37. IPN triangulation of GRB 250627A (short)
  38. GRB 250702A: Fermi GBM Detection
  39. GRB 250702D: Fermi GBM Final Localization Correction
  40. GRB 250702C: Fermi GBM Final Real-time Localization
  41. GRB 250702B: Fermi GBM Final Real-time Localization
  42. GRB 250702A: Fermi GBM Final Real-time Localization
  43. GRB 250628B: Swift-XRT observations
  44. GRB 250628B: SVOM/VT optical upper limit
  45. GRB 250628B: EP-FXT counterpart detection
  46. GRB 250627A: Insight-HXMT detection
  47. GRB 250627A: SVOM/GRM detection of a short burst
  48. GRB 250628A: REM optical/NIR upper limits
  49. GRB 250628C: Fermi GBM Final Real-time Localization
  50. GRB 250628B: SVOM detection of a long burst
  51. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  52. GRB 250628A: VLT/X-shooter upper limits
  53. GRB 250628A: Swift/UVOT Upper Limits
  54. GRB 250628A: Swift-XRT refined Analysis
  55. GRB 250628A: Enhanced Swift-XRT position
  56. GRB 250628A: Swift detection of a burst
  57. GRB 250625A: Leavitt Observatory afterglow detection
  58. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  59. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  60. GRB 250626A: Fermi GBM Final Real-time Localization
  61. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  62. GRB 250625A: SVOM/C-GFT upper limit in early phase
  63. GRB 250625A: GECAM-B detection
  64. GRB 250625A: Swift/UVOT Upper Limits
  65. GRB 250625A: ABObservatory afterglow detection
  66. GRB 250625A: OHP/T193 optical detection
  67. GRB 250625A: COLIBRÍ optical observations
  68. GRB 250625A: Fermi-LAT detection
  69. GRB 250625A: Swift-XRT refined Analysis
  70. GRB 250625A: JinShan optical observations
  71. GRB250625A: Fermi GBM Observation
  72. GRB 250625A: NOT z-band upper limit
  73. GRB 250625A: SVOM/VT optical confirmation
  74. GRB 250625A: SAO RAS possible optical afterglow
  75. GRB 250625A: Enhanced Swift-XRT position
  76. GRB 250625A: Swift detection of a burst
  77. GRB 250625A: Fermi GBM Final Real-time Localization
  78. GRB 250620A: AstroSat CZTI detection
  79. GRB 241018A: Maidanak optical observations
  80. GRB 250620C: AstroSat CZTI detection
  81. GRB 250624A: Fermi GBM Final Real-time Localization
  82. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  83. GRB 250623A: Fermi GBM Final Real-time Localization
  84. GRB 250521A: VZLUSAT-2 detection
  85. Konus-Wind detection of GRB 250620C
  86. IPN triangulation of GRB 250620C (long/bright)
  87. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  88. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  89. GRB 250621A: Fermi GBM Final Real-time Localization
  90. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  91. GRB 250620C: Fermi GBM Final Real-time Localization
  92. GRB 250620B: Fermi GBM Final Real-time Localization
  93. GRB 250620A: Fermi GBM Final Real-time Localization
  94. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  95. GRB 250617B: Nickel telescope optical observations
  96. GRB 250619B: Fermi GBM Final Real-time Localization
  97. GRB 250615A: Kilonova-Catcher optical upper limits
  98. GRB 250619A: Fermi GBM Final Real-time Localization
  99. GRB 250617B: Assy AZT-20 Optical Observations
  100. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis

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