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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"

36155 results found.

  1. GRB 250704B: Swift/UVOT Upper Limits
  2. GRB 250704A: Swift/UVOT Detection
  3. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  4. GRB 250704B: Insight-HXMT detection
  5. Konus-Wind detection of GRB 250703A
  6. IPN triangulation of GRB 250703A
  7. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  8. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  9. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  10. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  11. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  12. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  13. GRB 250702F: Kilonova-Catcher optical afterglow detection
  14. GRB 250702F: Monte Agliale Observatory optical observations
  15. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  16. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  17. EP250704a / GRB 250704B: JinShan optical observations
  18. GRB 250704A: SVOM/VT optical observation
  19. EP250704a / GRB 250704B: SAO RAS optical observations
  20. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  21. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  22. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  23. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  24. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  25. GRB 250702A: Insight-HXMT detection
  26. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  27. EP250704a / GRB250704B: Swift-XRT counterpart detection
  28. GRB 250704A: Swift-XRT afterglow detection
  29. GRB 250702B / EP2050702a: FTW optical and NIR observations
  30. Konus-Wind detection of GRB 250702F
  31. EP250704a / GRB 250704B - REM observations
  32. GRB 250702F: GROWTH-India Telescope optical observations
  33. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  34. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  35. EP250704a: Einstein Probe detection of an X-ray transient
  36. GRB 250704B: SVOM/GRM observation of a short burst
  37. GRB 250702F: optical photometry from Konkoly
  38. GRB 250704A: REM detection of the optical afterglow
  39. GRB 250702F: SVOM/VT optical observation
  40. GRB 250704A: SVOM detection of a burst
  41. GRB 250702F: Swift/UVOT Detection
  42. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  43. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  44. Fermi GRB 250703A: Global MASTER-Net observations report
  45. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  46. GRB 250702F: Swift-XRT refined Analysis
  47. GRB 250702F: Fermi GBM Observation
  48. GRB 250702F: Leavitt Observatory optical observations
  49. GRB 250702F: AKO Optical Afterglow Detection
  50. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  51. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  52. GRB 250702A: GECAM-B detection
  53. GRB 250702F: Skynet Optical Observations
  54. GRB 250424A: VIRT Optical Upper Limit
  55. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  56. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  57. GRB 250702F: TRT Optical Observation
  58. GRB 250703A: DDOTI Optical Upper Limit
  59. GRB 250702F: REM optical afterglow detection
  60. GRB 250702F: DDOTI Optical Observation
  61. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  62. GRB 250703A: Fermi GBM Final Real-time Localization
  63. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  64. GRB 250702F: COLIBRÍ Observations of the Afterglow
  65. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  66. Fermi GRB 250702E: Global MASTER-Net observations report
  67. Fermi GRB 250702B: Global MASTER-Net observations report
  68. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  69. GRB 250702F: Enhanced Swift-XRT position
  70. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  71. GRB 250702F: NOT observations of the optical afterglow
  72. GRB 250702F: MASTER optical afterglow observation
  73. Fermi GRB 250702F: Global MASTER-Net observations report
  74. Fermi GRB 250702C: Global MASTER-Net observations report
  75. GRB 250702F: GOTO optical counterpart detection
  76. GRB 250702F: Ondrejov D50 optical afterglow detection
  77. GRB 250702F: Swift detection of a burst with an optical counterpart
  78. Swift GRB 250702F: Global MASTER-Net observations report
  79. GRB 250702F: Fermi GBM Final Real-time Localization
  80. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  81. GRB 250702E: Fermi GBM Final Real-time Localization
  82. Konus-Wind detection of GRB 250627A
  83. IPN triangulation of GRB 250627A (short)
  84. GRB 250702A: Fermi GBM Detection
  85. GRB 250702D: Fermi GBM Final Localization Correction
  86. GRB 250702C: Fermi GBM Final Real-time Localization
  87. GRB 250702B: Fermi GBM Final Real-time Localization
  88. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  89. GRB 250702A: Fermi GBM Final Real-time Localization
  90. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  91. GRB 250628B: Swift-XRT observations
  92. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  93. GRB 250628B: SVOM/VT optical upper limit
  94. GRB 250628B: EP-FXT counterpart detection
  95. GRB 250627A: Insight-HXMT detection
  96. GRB 250627A: SVOM/GRM detection of a short burst
  97. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  98. GRB 250628A: REM optical/NIR upper limits
  99. GRB 250628C: Fermi GBM Final Real-time Localization
  100. GRB 250628B: SVOM detection of a long burst

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