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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"
  1. EP250704a / GRB250704B: Swift-XRT counterpart detection
  2. GRB 250704A: Swift-XRT afterglow detection
  3. GRB 250702B / EP2050702a: FTW optical and NIR observations
  4. Konus-Wind detection of GRB 250702F
  5. EP250704a / GRB 250704B - REM observations
  6. GRB 250702F: GROWTH-India Telescope optical observations
  7. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  8. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  9. EP250702a: WFST optical observations
  10. EP250704a: COLIBRÍ optical counterpart candidate
  11. EP250704a: Einstein Probe detection of an X-ray transient
  12. GRB 250704B: SVOM/GRM observation of a short burst
  13. GRB 250702F: optical photometry from Konkoly
  14. GRB 250704A: REM detection of the optical afterglow
  15. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  16. GRB 250702F: SVOM/VT optical observation
  17. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  18. GRB 250704A: SVOM detection of a burst
  19. GRB 250702F: Swift/UVOT Detection
  20. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  21. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  22. Fermi GRB 250703A: Global MASTER-Net observations report
  23. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  24. GRB 250702F: Swift-XRT refined Analysis
  25. GRB 250702F: Fermi GBM Observation
  26. GRB 250702F: Leavitt Observatory optical observations
  27. GRB 250702F: AKO Optical Afterglow Detection
  28. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  29. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  30. GRB 250702A: GECAM-B detection
  31. GRB 250702F: Skynet Optical Observations
  32. GRB 250424A: VIRT Optical Upper Limit
  33. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  34. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  35. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  36. GRB 250702F: TRT Optical Observation
  37. GRB 250703A: DDOTI Optical Upper Limit
  38. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  39. GRB 250702F: REM optical afterglow detection
  40. EP250702a: Global MASTER-Net observations report
  41. GRB 250702F: DDOTI Optical Observation
  42. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  43. GRB 250703A: Fermi GBM Final Real-time Localization
  44. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  45. GRB 250702F: COLIBRÍ Observations of the Afterglow
  46. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  47. Fermi GRB 250702E: Global MASTER-Net observations report
  48. Fermi GRB 250702B: Global MASTER-Net observations report
  49. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  50. GRB 250702F: Enhanced Swift-XRT position
  51. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  52. GRB 250702F: NOT observations of the optical afterglow
  53. GRB 250702F: MASTER optical afterglow observation
  54. Fermi GRB 250702F: Global MASTER-Net observations report
  55. Fermi GRB 250702C: Global MASTER-Net observations report
  56. GRB 250702F: GOTO optical counterpart detection
  57. GRB 250702F: Ondrejov D50 optical afterglow detection
  58. GRB 250702F: Swift detection of a burst with an optical counterpart
  59. Swift GRB 250702F: Global MASTER-Net observations report
  60. GRB 250702F: Fermi GBM Final Real-time Localization
  61. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  62. GRB 250702E: Fermi GBM Final Real-time Localization
  63. Konus-Wind detection of GRB 250627A
  64. IPN triangulation of GRB 250627A (short)
  65. GRB 250702A: Fermi GBM Detection
  66. GRB 250702D: Fermi GBM Final Localization Correction
  67. GRB 250702C: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  69. GRB 250702B: Fermi GBM Final Real-time Localization
  70. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  71. GRB 250702A: Fermi GBM Final Real-time Localization
  72. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  74. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  75. GRB 250628B: Swift-XRT observations
  76. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  77. GRB 250628B: SVOM/VT optical upper limit
  78. GRB 250628B: EP-FXT counterpart detection
  79. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  80. GRB 250627A: Insight-HXMT detection
  81. GRB 250627A: SVOM/GRM detection of a short burst
  82. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  83. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  84. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  85. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  87. GRB 250628A: REM optical/NIR upper limits
  88. GRB 250628C: Fermi GBM Final Real-time Localization
  89. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  90. GRB 250628B: SVOM detection of a long burst
  91. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  92. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  93. GRB 250628A: VLT/X-shooter upper limits
  94. GRB 250628A: Swift/UVOT Upper Limits
  95. GRB 250628A: Swift-XRT refined Analysis
  96. Fermi GRB 250626A: Global MASTER-Net observations report
  97. Swift GRB 250628A: Global MASTER-Net observations report
  98. GRB 250628A: Enhanced Swift-XRT position
  99. GRB 250628A: Swift detection of a burst
  100. GRB 250625A: Swift-BAT refined analysis

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