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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"

36143 results found.

  1. GRB 250702F: Kilonova-Catcher optical afterglow detection
  2. GRB 250702F: Monte Agliale Observatory optical observations
  3. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  4. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  5. EP250704a / GRB 250704B: JinShan optical observations
  6. GRB 250704A: SVOM/VT optical observation
  7. EP250704a / GRB 250704B: SAO RAS optical observations
  8. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  9. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  10. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  11. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  12. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  13. GRB 250702A: Insight-HXMT detection
  14. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  15. EP250704a / GRB250704B: Swift-XRT counterpart detection
  16. GRB 250704A: Swift-XRT afterglow detection
  17. GRB 250702B / EP2050702a: FTW optical and NIR observations
  18. Konus-Wind detection of GRB 250702F
  19. EP250704a / GRB 250704B - REM observations
  20. GRB 250702F: GROWTH-India Telescope optical observations
  21. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  22. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  23. EP250704a: Einstein Probe detection of an X-ray transient
  24. GRB 250704B: SVOM/GRM observation of a short burst
  25. GRB 250702F: optical photometry from Konkoly
  26. GRB 250704A: REM detection of the optical afterglow
  27. GRB 250702F: SVOM/VT optical observation
  28. GRB 250704A: SVOM detection of a burst
  29. GRB 250702F: Swift/UVOT Detection
  30. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  31. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  32. Fermi GRB 250703A: Global MASTER-Net observations report
  33. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  34. GRB 250702F: Swift-XRT refined Analysis
  35. GRB 250702F: Fermi GBM Observation
  36. GRB 250702F: Leavitt Observatory optical observations
  37. GRB 250702F: AKO Optical Afterglow Detection
  38. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  39. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  40. GRB 250702A: GECAM-B detection
  41. GRB 250702F: Skynet Optical Observations
  42. GRB 250424A: VIRT Optical Upper Limit
  43. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  44. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  45. GRB 250702F: TRT Optical Observation
  46. GRB 250703A: DDOTI Optical Upper Limit
  47. GRB 250702F: REM optical afterglow detection
  48. GRB 250702F: DDOTI Optical Observation
  49. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  50. GRB 250703A: Fermi GBM Final Real-time Localization
  51. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  52. GRB 250702F: COLIBRÍ Observations of the Afterglow
  53. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  54. Fermi GRB 250702E: Global MASTER-Net observations report
  55. Fermi GRB 250702B: Global MASTER-Net observations report
  56. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  57. GRB 250702F: Enhanced Swift-XRT position
  58. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  59. GRB 250702F: NOT observations of the optical afterglow
  60. GRB 250702F: MASTER optical afterglow observation
  61. Fermi GRB 250702F: Global MASTER-Net observations report
  62. Fermi GRB 250702C: Global MASTER-Net observations report
  63. GRB 250702F: GOTO optical counterpart detection
  64. GRB 250702F: Ondrejov D50 optical afterglow detection
  65. GRB 250702F: Swift detection of a burst with an optical counterpart
  66. Swift GRB 250702F: Global MASTER-Net observations report
  67. GRB 250702F: Fermi GBM Final Real-time Localization
  68. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  69. GRB 250702E: Fermi GBM Final Real-time Localization
  70. Konus-Wind detection of GRB 250627A
  71. IPN triangulation of GRB 250627A (short)
  72. GRB 250702A: Fermi GBM Detection
  73. GRB 250702D: Fermi GBM Final Localization Correction
  74. GRB 250702C: Fermi GBM Final Real-time Localization
  75. GRB 250702B: Fermi GBM Final Real-time Localization
  76. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  77. GRB 250702A: Fermi GBM Final Real-time Localization
  78. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  79. GRB 250628B: Swift-XRT observations
  80. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  81. GRB 250628B: SVOM/VT optical upper limit
  82. GRB 250628B: EP-FXT counterpart detection
  83. GRB 250627A: Insight-HXMT detection
  84. GRB 250627A: SVOM/GRM detection of a short burst
  85. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  86. GRB 250628A: REM optical/NIR upper limits
  87. GRB 250628C: Fermi GBM Final Real-time Localization
  88. GRB 250628B: SVOM detection of a long burst
  89. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  90. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  91. GRB 250628A: VLT/X-shooter upper limits
  92. GRB 250628A: Swift/UVOT Upper Limits
  93. GRB 250628A: Swift-XRT refined Analysis
  94. Fermi GRB 250626A: Global MASTER-Net observations report
  95. Swift GRB 250628A: Global MASTER-Net observations report
  96. GRB 250628A: Enhanced Swift-XRT position
  97. GRB 250628A: Swift detection of a burst
  98. GRB 250625A: Swift-BAT refined analysis
  99. GRB 250625A: Leavitt Observatory afterglow detection
  100. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB

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