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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"

36130 results found.

  1. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  2. EP250704a / GRB250704B: Swift-XRT counterpart detection
  3. GRB 250704A: Swift-XRT afterglow detection
  4. GRB 250702B / EP2050702a: FTW optical and NIR observations
  5. Konus-Wind detection of GRB 250702F
  6. EP250704a / GRB 250704B - REM observations
  7. GRB 250702F: GROWTH-India Telescope optical observations
  8. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  9. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  10. EP250704a: Einstein Probe detection of an X-ray transient
  11. GRB 250704B: SVOM/GRM observation of a short burst
  12. GRB 250702F: optical photometry from Konkoly
  13. GRB 250704A: REM detection of the optical afterglow
  14. GRB 250702F: SVOM/VT optical observation
  15. GRB 250704A: SVOM detection of a burst
  16. GRB 250702F: Swift/UVOT Detection
  17. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  18. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  19. Fermi GRB 250703A: Global MASTER-Net observations report
  20. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  21. GRB 250702F: Swift-XRT refined Analysis
  22. GRB 250702F: Fermi GBM Observation
  23. GRB 250702F: Leavitt Observatory optical observations
  24. GRB 250702F: AKO Optical Afterglow Detection
  25. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  26. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  27. GRB 250702A: GECAM-B detection
  28. GRB 250702F: Skynet Optical Observations
  29. GRB 250424A: VIRT Optical Upper Limit
  30. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  31. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  32. GRB 250702F: TRT Optical Observation
  33. GRB 250703A: DDOTI Optical Upper Limit
  34. GRB 250702F: REM optical afterglow detection
  35. GRB 250702F: DDOTI Optical Observation
  36. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  37. GRB 250703A: Fermi GBM Final Real-time Localization
  38. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  39. GRB 250702F: COLIBRÍ Observations of the Afterglow
  40. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  41. Fermi GRB 250702E: Global MASTER-Net observations report
  42. Fermi GRB 250702B: Global MASTER-Net observations report
  43. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  44. GRB 250702F: Enhanced Swift-XRT position
  45. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  46. GRB 250702F: NOT observations of the optical afterglow
  47. GRB 250702F: MASTER optical afterglow observation
  48. Fermi GRB 250702F: Global MASTER-Net observations report
  49. Fermi GRB 250702C: Global MASTER-Net observations report
  50. GRB 250702F: GOTO optical counterpart detection
  51. GRB 250702F: Ondrejov D50 optical afterglow detection
  52. GRB 250702F: Swift detection of a burst with an optical counterpart
  53. Swift GRB 250702F: Global MASTER-Net observations report
  54. GRB 250702F: Fermi GBM Final Real-time Localization
  55. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  56. GRB 250702E: Fermi GBM Final Real-time Localization
  57. Konus-Wind detection of GRB 250627A
  58. IPN triangulation of GRB 250627A (short)
  59. GRB 250702A: Fermi GBM Detection
  60. GRB 250702D: Fermi GBM Final Localization Correction
  61. GRB 250702C: Fermi GBM Final Real-time Localization
  62. GRB 250702B: Fermi GBM Final Real-time Localization
  63. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  64. GRB 250702A: Fermi GBM Final Real-time Localization
  65. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  66. GRB 250628B: Swift-XRT observations
  67. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  68. GRB 250628B: SVOM/VT optical upper limit
  69. GRB 250628B: EP-FXT counterpart detection
  70. GRB 250627A: Insight-HXMT detection
  71. GRB 250627A: SVOM/GRM detection of a short burst
  72. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  73. GRB 250628A: REM optical/NIR upper limits
  74. GRB 250628C: Fermi GBM Final Real-time Localization
  75. GRB 250628B: SVOM detection of a long burst
  76. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  77. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  78. GRB 250628A: VLT/X-shooter upper limits
  79. GRB 250628A: Swift/UVOT Upper Limits
  80. GRB 250628A: Swift-XRT refined Analysis
  81. Fermi GRB 250626A: Global MASTER-Net observations report
  82. Swift GRB 250628A: Global MASTER-Net observations report
  83. GRB 250628A: Enhanced Swift-XRT position
  84. GRB 250628A: Swift detection of a burst
  85. GRB 250625A: Swift-BAT refined analysis
  86. GRB 250625A: Leavitt Observatory afterglow detection
  87. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  88. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  89. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  90. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  91. GRB 250626A: Fermi GBM Final Real-time Localization
  92. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  93. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  94. GRB 250625A: SVOM/C-GFT upper limit in early phase
  95. GRB 250625A: GECAM-B detection
  96. GRB 250625A: Swift/UVOT Upper Limits
  97. GRB 250625A: ABObservatory afterglow detection
  98. GRB 250625A: OHP/T193 optical detection
  99. GRB 250625A: COLIBRÍ optical observations
  100. GRB 250625A: Fermi-LAT detection

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