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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"

3999 results found.

  1. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  2. Fermi trigger No 776849714: Global MASTER-Net observations report
  3. GRB 250818B: SVOM detection of a short burst
  4. GRB 250815A: Fermi GBM Final Localization
  5. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  6. GRB 250814A: Possible afterglow candidate from P200/WIRC
  7. Fermi trigger No 776818276: Global MASTER-Net observations report
  8. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  9. IceCube Alert 250813.14: Global MASTER-Net observations report
  10. Fermi GRB 250808A: Global MASTER-Net observations report
  11. Swift GRB250807.65: Global MASTER-Net observations report
  12. The EP-WXT trigger 01709198251 is likely a flaring star
  13. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  14. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  15. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  16. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  17. GRB 250728A: COLIBRÍ optical upper limit
  18. Fermi trigger No 775387550: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  20. GRB 250727A: EP-FXT counterpart detection
  21. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  22. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  23. Swift GRB 250725A: Global MASTER-Net OT detection
  24. Fermi GRB 250725A: Global MASTER-Net observations report
  25. Swift GRB 250725A: Global MASTER-Net observations report
  26. GRB 250721A: MAXI/GSC detection
  27. Fermi trigger No 774730635: Global MASTER-Net observations report
  28. GRB 270713A: Kitab and AbAO Optical Observations
  29. Konus-Wind detection of GRB 250716A
  30. GRB 250716A: GOTO tentative optical counterpart candidate
  31. GRB 250716A: Fermi GBM Observation
  32. GRB 250716A: Fermi GBM Final Real-time Localization
  33. GRB 250706B/C: 7DT Follow-up Observations
  34. Fermi GRB 250711A: Global MASTER-Net observations report
  35. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  36. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  37. IceCube-250706A: Global MASTER-Net observations report
  38. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  39. GRB 250702F: Fermi GBM Observation
  40. GRB 250702F: Leavitt Observatory optical observations
  41. EP250702a: Global MASTER-Net observations report
  42. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  43. Fermi GRB 250702F: Global MASTER-Net observations report
  44. Fermi GRB 250702C: Global MASTER-Net observations report
  45. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  46. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  47. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  48. GRB 250628B: SVOM detection of a long burst
  49. Fermi GRB 250626A: Global MASTER-Net observations report
  50. GRB 250625A: Leavitt Observatory afterglow detection
  51. Fermi trigger No 772190032: Global MASTER-Net observations report
  52. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  53. GRB 250619B: Fermi GBM Observation
  54. GRB 250615A/EP250615a: FTW optical and NIR observations
  55. GRB 250617B: Ondrejov D50 optical afterglow detection
  56. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  57. Fermi trigger No 771424081: Global MASTER-Net observations report
  58. EP250612a: Global MASTER-Net observations report
  59. EP250610a: SVOM/VT optical upper limit
  60. Fermi trigger No 771072240: Global MASTER-Net observations report
  61. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  62. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  63. Fermi trigger No 770867684: Global MASTER-Net observations report
  64. Konus-Wind detection of GRB 250601A
  65. GRB 250601A: Fermi GBM Observation
  66. Fermi GRB 250601A: Global MASTER-Net observations report
  67. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  68. GRB 250601A: Fermi GBM Final Real-time Localization
  69. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  70. GRB 250530A: SVOM/VT optical upper limit
  71. GRB 250529B: Fermi GBM Final Real-time Localization
  72. GRB 250529A: Fermi GBM Final Real-time Localization
  73. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  74. Fermi GRB 250522B: Global MASTER-Net observations report
  75. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. Konus-Wind detection of GRB 250516A
  77. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  78. GRB 250516A: Swift detection of a burst
  79. GRB 250516A: Fermi GBM Final Real-time Localization
  80. GRB 250507B: AstroSat CZTI detection
  81. Fermi GRB 250510C: Global MASTER-Net observations report
  82. Fermi GRB 250510B: Global MASTER-Net observations report
  83. GRB 250509A: Fermi GBM Final Real-time Localization
  84. GRB 250506A: NOT optical upper limits
  85. GRB 250506A: Swift XRT observations and possible counterpart detection
  86. GRB 250506A: TRT optical observations
  87. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  88. GRB 250504A: MeerLICHT optical afterglow detection
  89. Fermi GRB 250504A: Global MASTER-Net observations report
  90. Swift GRB250504.98: Global MASTER-Net observations report
  91. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  92. GRB 250430A: Leavitt Observatory optical upper limit
  93. GRB 250430A : MITSuME Akeno optical upper limits
  94. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 250430A: AKO Optical Afterglow Detection
  96. Swift GRB250430.73: Global MASTER-Net observations report
  97. EP250427a/GRB250427A: HCT optical follow-up
  98. EP250428b: SVOM/VT upper limit
  99. EP250428b: SAO RAS optical upper limit
  100. EP250428b: LAST optical upper limit

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