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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"

39057 results found.

  1. EP250704a / GRB 250704B: JinShan optical observations
  2. GRB 250704A: SVOM/VT optical observation
  3. EP250704a / GRB 250704B: SAO RAS optical observations
  4. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  5. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  6. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  7. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  8. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  9. GRB 250702A: Insight-HXMT detection
  10. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  11. EP250704a / GRB250704B: Swift-XRT counterpart detection
  12. GRB 250704A: Swift-XRT afterglow detection
  13. GRB 250702B / EP2050702a: FTW optical and NIR observations
  14. Konus-Wind detection of GRB 250702F
  15. EP250704a / GRB 250704B - REM observations
  16. GRB 250702F: GROWTH-India Telescope optical observations
  17. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  18. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  19. EP250704a: COLIBRÍ optical counterpart candidate
  20. EP250704a: Einstein Probe detection of an X-ray transient
  21. GRB 250704B: SVOM/GRM observation of a short burst
  22. GRB 250702F: optical photometry from Konkoly
  23. GRB 250704A: REM detection of the optical afterglow
  24. GRB 250702F: SVOM/VT optical observation
  25. GRB 250704A: SVOM detection of a burst
  26. GRB 250702F: Swift/UVOT Detection
  27. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  28. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  29. Fermi GRB 250703A: Global MASTER-Net observations report
  30. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  31. GRB 250702F: Swift-XRT refined Analysis
  32. GRB 250702F: Fermi GBM Observation
  33. GRB 250702F: Leavitt Observatory optical observations
  34. GRB 250702F: AKO Optical Afterglow Detection
  35. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  36. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  37. GRB 250702A: GECAM-B detection
  38. GRB 250702F: Skynet Optical Observations
  39. GRB 250424A: VIRT Optical Upper Limit
  40. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  41. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  42. GRB 250702F: TRT Optical Observation
  43. GRB 250703A: DDOTI Optical Upper Limit
  44. GRB 250702F: REM optical afterglow detection
  45. EP250702a: Global MASTER-Net observations report
  46. GRB 250702F: DDOTI Optical Observation
  47. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  48. GRB 250703A: Fermi GBM Final Real-time Localization
  49. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  50. GRB 250702F: COLIBRÍ Observations of the Afterglow
  51. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  52. Fermi GRB 250702E: Global MASTER-Net observations report
  53. Fermi GRB 250702B: Global MASTER-Net observations report
  54. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  55. GRB 250702F: Enhanced Swift-XRT position
  56. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  57. GRB 250702F: NOT observations of the optical afterglow
  58. GRB 250702F: MASTER optical afterglow observation
  59. Fermi GRB 250702F: Global MASTER-Net observations report
  60. Fermi GRB 250702C: Global MASTER-Net observations report
  61. GRB 250702F: GOTO optical counterpart detection
  62. GRB 250702F: Ondrejov D50 optical afterglow detection
  63. GRB 250702F: Swift detection of a burst with an optical counterpart
  64. Swift GRB 250702F: Global MASTER-Net observations report
  65. GRB 250702F: Fermi GBM Final Real-time Localization
  66. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  67. GRB 250702E: Fermi GBM Final Real-time Localization
  68. Konus-Wind detection of GRB 250627A
  69. IPN triangulation of GRB 250627A (short)
  70. GRB 250702A: Fermi GBM Detection
  71. GRB 250702D: Fermi GBM Final Localization Correction
  72. GRB 250702C: Fermi GBM Final Real-time Localization
  73. GRB 250702B: Fermi GBM Final Real-time Localization
  74. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  75. GRB 250702A: Fermi GBM Final Real-time Localization
  76. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  77. GRB 250628B: Swift-XRT observations
  78. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  79. GRB 250628B: SVOM/VT optical upper limit
  80. GRB 250628B: EP-FXT counterpart detection
  81. GRB 250627A: Insight-HXMT detection
  82. GRB 250627A: SVOM/GRM detection of a short burst
  83. GRB 250628A: REM optical/NIR upper limits
  84. GRB 250628C: Fermi GBM Final Real-time Localization
  85. GRB 250628B: SVOM detection of a long burst
  86. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  87. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  88. GRB 250628A: VLT/X-shooter upper limits
  89. GRB 250628A: Swift/UVOT Upper Limits
  90. GRB 250628A: Swift-XRT refined Analysis
  91. Fermi GRB 250626A: Global MASTER-Net observations report
  92. Swift GRB 250628A: Global MASTER-Net observations report
  93. GRB 250628A: Enhanced Swift-XRT position
  94. GRB 250628A: Swift detection of a burst
  95. GRB 250625A: Swift-BAT refined analysis
  96. GRB 250625A: Leavitt Observatory afterglow detection
  97. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  98. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  99. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  100. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy

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