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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"

26237 results found.

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

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