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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"

26336 results found.

  1. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  2. Fermi GRB 251202B: Global MASTER-Net observations report
  3. IPN triangulation of GRB 251129B (short/hard)
  4. GRB251129A/EP251129a: Swift UVOT detection
  5. GRB 251202A: Fermi GBM Observation
  6. GRB 251202A: Swift/UVOT Detection
  7. GRB 251201B: Kilonova-Catcher optical afterglow detection
  8. GRB 251201B: Swift/UVOT Detection
  9. GRB 251130B: Glowbug gamma-ray detection
  10. EP251130a: continued NOT optical observations indicate steep fading phase
  11. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  12. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  13. GRB 251126A: SAO RAS optical marginal detection
  14. GRB 251202A: Swift-XRT afterglow detection
  15. EP251129a/GRB 251129A: NOWT Detection
  16. GRB 251126A: SVOM/VT optical observation
  17. EP251130a: SVOM/VT optical observation
  18. Fermi GRB 251202A: Global MASTER-Net observations report
  19. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  20. GRB 251201B: Swift-XRT refined Analysis
  21. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 251201A: SVOM/GRM observation of a burst
  23. GRB 251201B: SVOM/VT optical fading
  24. Swift GRB 251201B : MASTER optical counterpart detection
  25. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  26. Swift GRB 251201B: Global MASTER-Net observations report
  27. GRB 251201B: Enhanced Swift-XRT position
  28. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  29. GRB 251201B: Swift detection of a burst with an optical counterpart
  30. GRB 251201B: Fermi GBM Final Real-time Localization
  31. EP251130a: Mondy optical observations
  32. EP251130a: Optical detections with Kinder observations
  33. SVOM GRB251201.19: Global MASTER-Net observations report
  34. EP251130a: SAO RAS optical observations
  35. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  36. EP251130A: Optical observation from 1.3m DFOT
  37. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  38. EP251130a: JinShan optical observations
  39. GRB 251201A: MAXI/GSC detection
  40. Fermi GRB 251130B: Global MASTER-Net observations report
  41. GRB 251127A: SVOM/GRM observation
  42. IceCube Alert 251130.75: Global MASTER-Net observations report
  43. EP251130a: Swift-XRT counterpart detection
  44. EP251130a: Global MASTER-Net observations report
  45. EP251130a: COLIBRÍ optical counterpart candidate
  46. EP251130a: Einstein Probe detection of an X-ray transient
  47. GRB 251129A / EP251129a: SAO RAS optical observations
  48. GRB 251126A: SAO RAS optical observations
  49. GRB 251128A: SVOM/GRM observation of a long burst
  50. SVOM GRB 251129A : MASTER optical counterpart detection
  51. GRB 251129A: Swift-XRT afterglow detection
  52. EP251129a: Global MASTER-Net observations report
  53. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  54. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  55. GRB 251128A: Fermi GBM Observation
  56. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  57. GRB 251129A: SVOM detection of a burst
  58. SVOM GRB251129A: Global MASTER-Net observations report
  59. GRB 251129A: SVOM detection of a burst
  60. GRB 251126A: Swift-BAT refined analysis
  61. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  62. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  63. Fermi GRB 251128A: Global MASTER-Net observations report
  64. GRB 251127A: Glowbug gamma-ray detection
  65. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  66. GRB 251126A: further SAO RAS optical observations
  67. GRB 251126A NUTTelA-TAO Early Measurements
  68. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  69. GRB251126A: MAO/AZT-22 optical observations
  70. GRB251126A: Continued optical observation from 1.3m DFOT
  71. GRB 251126A: Swift/UVOT Detection
  72. GRB 251126A: Mondy and SAO RAS optical observations
  73. GRB 251126A: Swift-XRT refined Analysis
  74. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  75. GRB 251126A: NOT optical observations
  76. GRB 251126A: 1.3m DFOT optical afterglow detection
  77. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  78. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  79. Fermi GRB 251127A: Global MASTER-Net observations report
  80. GRB 251126A: Enhanced Swift-XRT position
  81. GRB 251126A: Kilonova-Catcher optical afterglow detection
  82. GRB 251126A: Nanshan/HMT optical afterglow detection
  83. Swift GRB 251126A: Global MASTER-Net observations report
  84. GRB 251121A: Fermi GBM Observation
  85. GRB 251126A: GIT discovery of the likely optical afterglow
  86. GRB 251126A: Swift detection of a burst
  87. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  88. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  89. EP251124b: NOT r- and z-band optical upper limits
  90. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  91. Fermi GRB 251125B: Global MASTER-Net observations report
  92. EP251124b: Global MASTER-Net observations report
  93. EP251124b: EP-WXT detection of a fast X-ray transient
  94. EP251124a: Xinglong GWAC-F60A optical observation
  95. Fermi GRB 251125A: Global MASTER-Net observations report
  96. EP251124a: NOT r- and z-band optical upper limits
  97. EP251124a: Global MASTER-Net observations report
  98. EP251124a: Swift-XRT observations
  99. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  100. EP251124a: Optical upper limit with Kinder observations

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