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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"

4179 results found.

  1. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  2. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  3. Swift GRB 250725A: Global MASTER-Net OT detection
  4. Fermi GRB 250725A: Global MASTER-Net observations report
  5. Swift GRB 250725A: Global MASTER-Net observations report
  6. GRB 250721A: MAXI/GSC detection
  7. Fermi trigger No 774730635: Global MASTER-Net observations report
  8. GRB 270713A: Kitab and AbAO Optical Observations
  9. Konus-Wind detection of GRB 250716A
  10. GRB 250716A: GOTO tentative optical counterpart candidate
  11. GRB 250716A: Fermi GBM Observation
  12. GRB 250716A: Fermi GBM Final Real-time Localization
  13. GRB 250706B/C: 7DT Follow-up Observations
  14. Fermi GRB 250711A: Global MASTER-Net observations report
  15. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  16. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  17. IceCube-250706A: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  19. GRB 250702F: Fermi GBM Observation
  20. GRB 250702F: Leavitt Observatory optical observations
  21. EP250702a: Global MASTER-Net observations report
  22. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  23. Fermi GRB 250702F: Global MASTER-Net observations report
  24. Fermi GRB 250702C: Global MASTER-Net observations report
  25. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  26. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  28. GRB 250628B: SVOM detection of a long burst
  29. Fermi GRB 250626A: Global MASTER-Net observations report
  30. GRB 250625A: Leavitt Observatory afterglow detection
  31. Fermi trigger No 772190032: Global MASTER-Net observations report
  32. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  33. GRB 250619B: Fermi GBM Observation
  34. GRB 250615A/EP250615a: FTW optical and NIR observations
  35. GRB 250617B: Ondrejov D50 optical afterglow detection
  36. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  37. Fermi trigger No 771424081: Global MASTER-Net observations report
  38. EP250612a: Global MASTER-Net observations report
  39. EP250610a: SVOM/VT optical upper limit
  40. Fermi trigger No 771072240: Global MASTER-Net observations report
  41. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  42. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  43. Fermi trigger No 770867684: Global MASTER-Net observations report
  44. Konus-Wind detection of GRB 250601A
  45. GRB 250601A: Fermi GBM Observation
  46. Fermi GRB 250601A: Global MASTER-Net observations report
  47. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  48. GRB 250601A: Fermi GBM Final Real-time Localization
  49. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  50. GRB 250530A: SVOM/VT optical upper limit
  51. GRB 250529B: Fermi GBM Final Real-time Localization
  52. GRB 250529A: Fermi GBM Final Real-time Localization
  53. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  54. Fermi GRB 250522B: Global MASTER-Net observations report
  55. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  56. Konus-Wind detection of GRB 250516A
  57. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  58. GRB 250516A: Swift detection of a burst
  59. GRB 250516A: Fermi GBM Final Real-time Localization
  60. GRB 250507B: AstroSat CZTI detection
  61. Fermi GRB 250510C: Global MASTER-Net observations report
  62. Fermi GRB 250510B: Global MASTER-Net observations report
  63. GRB 250509A: Fermi GBM Final Real-time Localization
  64. GRB 250506A: NOT optical upper limits
  65. GRB 250506A: Swift XRT observations and possible counterpart detection
  66. GRB 250506A: TRT optical observations
  67. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  68. GRB 250504A: MeerLICHT optical afterglow detection
  69. Fermi GRB 250504A: Global MASTER-Net observations report
  70. Swift GRB250504.98: Global MASTER-Net observations report
  71. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  72. GRB 250430A: Leavitt Observatory optical upper limit
  73. GRB 250430A : MITSuME Akeno optical upper limits
  74. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 250430A: AKO Optical Afterglow Detection
  76. Swift GRB250430.73: Global MASTER-Net observations report
  77. EP250427a/GRB250427A: HCT optical follow-up
  78. EP250428b: SVOM/VT upper limit
  79. EP250428b: SAO RAS optical upper limit
  80. EP250428b: LAST optical upper limit
  81. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  82. EP250428b: Global MASTER-Net observations report
  83. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  84. EP250427a: TRT optical counterpart detection
  85. EP 250427a: BOOTES-7 optical afterglow candidate
  86. GRB 250424A: SVOM/VT optical observation
  87. GRB 250419A: Mondy Optical Observations
  88. GRB 250424A: Swift/UVOT Detection
  89. GRB250419A: VLA radio detection
  90. GRB 250419A: Mephisto Multi-band Optical Detection
  91. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  92. GRB 250419A: Optical Observations via Virtual Telescope Project
  93. IceCube Alert 250421.71: Global MASTER-Net observations report
  94. EP250421a: JinShan likely optical counterpart
  95. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  96. GRB 250419A: Swift/UVOT Follow up
  97. GRB 250419A: AKO Optical Afterglow Detection
  98. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  99. GRB 250419A: SVOM detection of a soft burst
  100. GRB 250412A: AstroSat CZTI detection

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