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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"

4183 results found.

  1. GRB 250728A: COLIBRÍ optical upper limit
  2. Fermi trigger No 775387550: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  4. GRB 250727A: EP-FXT counterpart detection
  5. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  6. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  7. Swift GRB 250725A: Global MASTER-Net OT detection
  8. Fermi GRB 250725A: Global MASTER-Net observations report
  9. Swift GRB 250725A: Global MASTER-Net observations report
  10. GRB 250721A: MAXI/GSC detection
  11. Fermi trigger No 774730635: Global MASTER-Net observations report
  12. GRB 270713A: Kitab and AbAO Optical Observations
  13. Konus-Wind detection of GRB 250716A
  14. GRB 250716A: GOTO tentative optical counterpart candidate
  15. GRB 250716A: Fermi GBM Observation
  16. GRB 250716A: Fermi GBM Final Real-time Localization
  17. GRB 250706B/C: 7DT Follow-up Observations
  18. Fermi GRB 250711A: Global MASTER-Net observations report
  19. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  20. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  21. IceCube-250706A: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  23. GRB 250702F: Fermi GBM Observation
  24. GRB 250702F: Leavitt Observatory optical observations
  25. EP250702a: Global MASTER-Net observations report
  26. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  27. Fermi GRB 250702F: Global MASTER-Net observations report
  28. Fermi GRB 250702C: Global MASTER-Net observations report
  29. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  30. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  32. GRB 250628B: SVOM detection of a long burst
  33. Fermi GRB 250626A: Global MASTER-Net observations report
  34. GRB 250625A: Leavitt Observatory afterglow detection
  35. Fermi trigger No 772190032: Global MASTER-Net observations report
  36. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  37. GRB 250619B: Fermi GBM Observation
  38. GRB 250615A/EP250615a: FTW optical and NIR observations
  39. GRB 250617B: Ondrejov D50 optical afterglow detection
  40. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  41. Fermi trigger No 771424081: Global MASTER-Net observations report
  42. EP250612a: Global MASTER-Net observations report
  43. EP250610a: SVOM/VT optical upper limit
  44. Fermi trigger No 771072240: Global MASTER-Net observations report
  45. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  46. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  47. Fermi trigger No 770867684: Global MASTER-Net observations report
  48. Konus-Wind detection of GRB 250601A
  49. GRB 250601A: Fermi GBM Observation
  50. Fermi GRB 250601A: Global MASTER-Net observations report
  51. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  52. GRB 250601A: Fermi GBM Final Real-time Localization
  53. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  54. GRB 250530A: SVOM/VT optical upper limit
  55. GRB 250529B: Fermi GBM Final Real-time Localization
  56. GRB 250529A: Fermi GBM Final Real-time Localization
  57. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  58. Fermi GRB 250522B: Global MASTER-Net observations report
  59. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. Konus-Wind detection of GRB 250516A
  61. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  62. GRB 250516A: Swift detection of a burst
  63. GRB 250516A: Fermi GBM Final Real-time Localization
  64. GRB 250507B: AstroSat CZTI detection
  65. Fermi GRB 250510C: Global MASTER-Net observations report
  66. Fermi GRB 250510B: Global MASTER-Net observations report
  67. GRB 250509A: Fermi GBM Final Real-time Localization
  68. GRB 250506A: NOT optical upper limits
  69. GRB 250506A: Swift XRT observations and possible counterpart detection
  70. GRB 250506A: TRT optical observations
  71. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  72. GRB 250504A: MeerLICHT optical afterglow detection
  73. Fermi GRB 250504A: Global MASTER-Net observations report
  74. Swift GRB250504.98: Global MASTER-Net observations report
  75. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  76. GRB 250430A: Leavitt Observatory optical upper limit
  77. GRB 250430A : MITSuME Akeno optical upper limits
  78. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 250430A: AKO Optical Afterglow Detection
  80. Swift GRB250430.73: Global MASTER-Net observations report
  81. EP250427a/GRB250427A: HCT optical follow-up
  82. EP250428b: SVOM/VT upper limit
  83. EP250428b: SAO RAS optical upper limit
  84. EP250428b: LAST optical upper limit
  85. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  86. EP250428b: Global MASTER-Net observations report
  87. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  88. EP250427a: TRT optical counterpart detection
  89. EP 250427a: BOOTES-7 optical afterglow candidate
  90. GRB 250424A: SVOM/VT optical observation
  91. GRB 250419A: Mondy Optical Observations
  92. GRB 250424A: Swift/UVOT Detection
  93. GRB250419A: VLA radio detection
  94. GRB 250419A: Mephisto Multi-band Optical Detection
  95. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  96. GRB 250419A: Optical Observations via Virtual Telescope Project
  97. IceCube Alert 250421.71: Global MASTER-Net observations report
  98. EP250421a: JinShan likely optical counterpart
  99. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  100. GRB 250419A: Swift/UVOT Follow up

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