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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"

36152 results found.

  1. Konus-Wind detection of GRB 250703A
  2. IPN triangulation of GRB 250703A
  3. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  4. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  5. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  6. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  7. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  8. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  9. GRB 250702F: Kilonova-Catcher optical afterglow detection
  10. GRB 250702F: Monte Agliale Observatory optical observations
  11. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  12. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  13. EP250704a / GRB 250704B: JinShan optical observations
  14. GRB 250704A: SVOM/VT optical observation
  15. EP250704a / GRB 250704B: SAO RAS optical observations
  16. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  17. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  18. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  19. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  20. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  21. GRB 250702A: Insight-HXMT detection
  22. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  23. EP250704a / GRB250704B: Swift-XRT counterpart detection
  24. GRB 250704A: Swift-XRT afterglow detection
  25. GRB 250702B / EP2050702a: FTW optical and NIR observations
  26. Konus-Wind detection of GRB 250702F
  27. EP250704a / GRB 250704B - REM observations
  28. GRB 250702F: GROWTH-India Telescope optical observations
  29. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  30. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  31. EP250704a: Einstein Probe detection of an X-ray transient
  32. GRB 250704B: SVOM/GRM observation of a short burst
  33. GRB 250702F: optical photometry from Konkoly
  34. GRB 250704A: REM detection of the optical afterglow
  35. GRB 250702F: SVOM/VT optical observation
  36. GRB 250704A: SVOM detection of a burst
  37. GRB 250702F: Swift/UVOT Detection
  38. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  39. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  40. Fermi GRB 250703A: Global MASTER-Net observations report
  41. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  42. GRB 250702F: Swift-XRT refined Analysis
  43. GRB 250702F: Fermi GBM Observation
  44. GRB 250702F: Leavitt Observatory optical observations
  45. GRB 250702F: AKO Optical Afterglow Detection
  46. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  47. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  48. GRB 250702A: GECAM-B detection
  49. GRB 250702F: Skynet Optical Observations
  50. GRB 250424A: VIRT Optical Upper Limit
  51. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  52. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  53. GRB 250702F: TRT Optical Observation
  54. GRB 250703A: DDOTI Optical Upper Limit
  55. GRB 250702F: REM optical afterglow detection
  56. GRB 250702F: DDOTI Optical Observation
  57. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  58. GRB 250703A: Fermi GBM Final Real-time Localization
  59. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  60. GRB 250702F: COLIBRÍ Observations of the Afterglow
  61. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  62. Fermi GRB 250702E: Global MASTER-Net observations report
  63. Fermi GRB 250702B: Global MASTER-Net observations report
  64. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  65. GRB 250702F: Enhanced Swift-XRT position
  66. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  67. GRB 250702F: NOT observations of the optical afterglow
  68. GRB 250702F: MASTER optical afterglow observation
  69. Fermi GRB 250702F: Global MASTER-Net observations report
  70. Fermi GRB 250702C: Global MASTER-Net observations report
  71. GRB 250702F: GOTO optical counterpart detection
  72. GRB 250702F: Ondrejov D50 optical afterglow detection
  73. GRB 250702F: Swift detection of a burst with an optical counterpart
  74. Swift GRB 250702F: Global MASTER-Net observations report
  75. GRB 250702F: Fermi GBM Final Real-time Localization
  76. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  77. GRB 250702E: Fermi GBM Final Real-time Localization
  78. Konus-Wind detection of GRB 250627A
  79. IPN triangulation of GRB 250627A (short)
  80. GRB 250702A: Fermi GBM Detection
  81. GRB 250702D: Fermi GBM Final Localization Correction
  82. GRB 250702C: Fermi GBM Final Real-time Localization
  83. GRB 250702B: Fermi GBM Final Real-time Localization
  84. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  85. GRB 250702A: Fermi GBM Final Real-time Localization
  86. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  87. GRB 250628B: Swift-XRT observations
  88. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  89. GRB 250628B: SVOM/VT optical upper limit
  90. GRB 250628B: EP-FXT counterpart detection
  91. GRB 250627A: Insight-HXMT detection
  92. GRB 250627A: SVOM/GRM detection of a short burst
  93. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  94. GRB 250628A: REM optical/NIR upper limits
  95. GRB 250628C: Fermi GBM Final Real-time Localization
  96. GRB 250628B: SVOM detection of a long burst
  97. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  98. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  99. GRB 250628A: VLT/X-shooter upper limits
  100. GRB 250628A: Swift/UVOT Upper Limits

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