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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"
  1. GRB 251129B: AstroSat CZTI detection
  2. GRB 251202A: Fermi GBM Observation
  3. GRB 251202A: Swift/UVOT Detection
  4. GRB 251201B: Kilonova-Catcher optical afterglow detection
  5. GRB 251201B: Swift/UVOT Detection
  6. GRB 251130B: Glowbug gamma-ray detection
  7. GRB 251201B: GECAM-B observation of a long burst
  8. EP251130a: continued NOT optical observations indicate steep fading phase
  9. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  10. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  11. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  12. GRB 251202A: GOTO optical afterglow detection
  13. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  14. GRB 251201A: GECAM-B observation of a burst
  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. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  21. Fermi GRB 251202A: Global MASTER-Net observations report
  22. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  23. GRB 251201B: Swift-XRT refined Analysis
  24. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  25. The EP-WXT trigger 01709249064: Las Cumbres discovery of the optical counterpart
  26. GRB 251202A: Fermi GBM Final Real-time Localization
  27. GRB 251201A: SVOM/GRM observation of a burst
  28. GRB 251201B: SVOM/VT optical fading
  29. Swift GRB 251201B : MASTER optical counterpart detection
  30. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  31. Swift GRB 251201B: Global MASTER-Net observations report
  32. GRB 251201B: Enhanced Swift-XRT position
  33. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  34. GRB 251130B: AstroSat CZTI detection
  35. GRB 251201B: Swift detection of a burst with an optical counterpart
  36. GRB 251201B: Fermi GBM Final Real-time Localization
  37. EP251130a: Mondy optical observations
  38. EP251130a: Optical detections with Kinder observations
  39. SVOM GRB251201.19: Global MASTER-Net observations report
  40. EP251130a: SAO RAS optical observations
  41. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  42. EP251130a: KAIT optical observations
  43. EP251130A: Optical observation from 1.3m DFOT
  44. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP251130a: JinShan optical observations
  46. GRB 251201A: MAXI/GSC detection
  47. Fermi GRB 251130B: Global MASTER-Net observations report
  48. GRB 251127A: SVOM/GRM observation
  49. IceCube Alert 251130.75: Global MASTER-Net observations report
  50. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  51. EP251130a: Swift-XRT counterpart detection
  52. GRB 251130B: Fermi GBM Final Localization Correction
  53. EP251130a: Global MASTER-Net observations report
  54. GRB 251130B: Fermi GBM Final Real-time Localization
  55. EP251130a: COLIBRÍ optical counterpart candidate
  56. EP251130a: Einstein Probe detection of an X-ray transient
  57. EP251129a/GRB 251129A: EP-FXT follow-up observations
  58. GRB 251130A: Fermi GBM Final Real-time Localization
  59. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  60. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  61. GRB 251128A: AstroSat CZTI detection
  62. GRB 251129A / EP251129a: SAO RAS optical observations
  63. GRB 251126A: SAO RAS optical observations
  64. GRB 251128A: GECAM-B detection
  65. GRB 251128A: SVOM/GRM observation of a long burst
  66. GRB 251128A: Insight-HXMT/HE detection
  67. SVOM GRB 251129A : MASTER optical counterpart detection
  68. GRB 251129A: Swift-XRT afterglow detection
  69. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  70. Swift trigger 1418333 is not an astrophysical source
  71. GRB 251129A: Swift ToO observations
  72. GRB 251129A / EP251129a: SVOM/VT optical fading
  73. EP251129a: Global MASTER-Net observations report
  74. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  75. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  76. GRB 251129A: Correction to the position of the optical counterpar
  77. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  78. GRB 251128A: Fermi GBM Observation
  79. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  80. GRB 251129A: SVOM detection of a burst
  81. SVOM GRB251129A: Global MASTER-Net observations report
  82. GRB 251129A: SVOM detection of a burst
  83. GRB 251126A: Swift-BAT refined analysis
  84. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  85. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  86. Fermi GRB 251128A: Global MASTER-Net observations report
  87. GRB 251127A: Glowbug gamma-ray detection
  88. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  89. GRB 251126A: further SAO RAS optical observations
  90. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  91. GRB 251126A NUTTelA-TAO Early Measurements
  92. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  93. GRB251126A: MAO/AZT-22 optical observations
  94. GRB 251128A: Fermi GBM Final Real-time Localization
  95. GRB251126A: Continued optical observation from 1.3m DFOT
  96. GRB 251126A: Swift/UVOT Detection
  97. EP251124a: Pan-STARRS ri-band imaging and photometry
  98. GRB 251126A: Mondy and SAO RAS optical observations
  99. GRB 251126A: Swift-XRT refined Analysis
  100. GRB 251126A : MITSuME Akeno optical afterglow candidate detection

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