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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 251202A: GOTO optical afterglow detection
  2. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  3. GRB 251201A: GECAM-B observation of a burst
  4. GRB 251126A: SAO RAS optical marginal detection
  5. GRB 251202A: Swift-XRT afterglow detection
  6. EP251129a/GRB 251129A: NOWT Detection
  7. GRB 251126A: SVOM/VT optical observation
  8. EP251130a: SVOM/VT optical observation
  9. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  10. Fermi GRB 251202A: Global MASTER-Net observations report
  11. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  12. GRB 251201B: Swift-XRT refined Analysis
  13. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  14. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  15. GRB 251202A: Fermi GBM Final Real-time Localization
  16. GRB 251201A: SVOM/GRM observation of a burst
  17. GRB 251201B: SVOM/VT optical fading
  18. Swift GRB 251201B : MASTER optical counterpart detection
  19. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  20. Swift GRB 251201B: Global MASTER-Net observations report
  21. GRB 251201B: Enhanced Swift-XRT position
  22. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  23. GRB 251130B: AstroSat CZTI detection
  24. GRB 251201B: Swift detection of a burst with an optical counterpart
  25. GRB 251201B: Fermi GBM Final Real-time Localization
  26. EP251130a: Mondy optical observations
  27. EP251130a: Optical detections with Kinder observations
  28. SVOM GRB251201.19: Global MASTER-Net observations report
  29. EP251130a: SAO RAS optical observations
  30. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  31. EP251130a: KAIT optical observations
  32. EP251130A: Optical observation from 1.3m DFOT
  33. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  34. EP251130a: JinShan optical observations
  35. GRB 251201A: MAXI/GSC detection
  36. Fermi GRB 251130B: Global MASTER-Net observations report
  37. GRB 251127A: SVOM/GRM observation
  38. IceCube Alert 251130.75: Global MASTER-Net observations report
  39. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  40. EP251130a: Swift-XRT counterpart detection
  41. GRB 251130B: Fermi GBM Final Localization Correction
  42. EP251130a: Global MASTER-Net observations report
  43. GRB 251130B: Fermi GBM Final Real-time Localization
  44. EP251130a: COLIBRÍ optical counterpart candidate
  45. EP251130a: Einstein Probe detection of an X-ray transient
  46. EP251129a/GRB 251129A: EP-FXT follow-up observations
  47. GRB 251130A: Fermi GBM Final Real-time Localization
  48. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  49. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  50. GRB 251128A: AstroSat CZTI detection
  51. GRB 251129A / EP251129a: SAO RAS optical observations
  52. GRB 251126A: SAO RAS optical observations
  53. GRB 251128A: GECAM-B detection
  54. GRB 251128A: SVOM/GRM observation of a long burst
  55. GRB 251128A: Insight-HXMT/HE detection
  56. SVOM GRB 251129A : MASTER optical counterpart detection
  57. GRB 251129A: Swift-XRT afterglow detection
  58. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  59. Swift trigger 1418333 is not an astrophysical source
  60. GRB 251129A: Swift ToO observations
  61. GRB 251129A / EP251129a: SVOM/VT optical fading
  62. EP251129a: Global MASTER-Net observations report
  63. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  64. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  65. GRB 251129A: Correction to the position of the optical counterpar
  66. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  67. GRB 251128A: Fermi GBM Observation
  68. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  69. GRB 251129A: SVOM detection of a burst
  70. SVOM GRB251129A: Global MASTER-Net observations report
  71. GRB 251129A: SVOM detection of a burst
  72. GRB 251126A: Swift-BAT refined analysis
  73. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  74. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  75. Fermi GRB 251128A: Global MASTER-Net observations report
  76. GRB 251127A: Glowbug gamma-ray detection
  77. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  78. GRB 251126A: further SAO RAS optical observations
  79. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  80. GRB 251126A NUTTelA-TAO Early Measurements
  81. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  82. GRB251126A: MAO/AZT-22 optical observations
  83. GRB 251128A: Fermi GBM Final Real-time Localization
  84. GRB251126A: Continued optical observation from 1.3m DFOT
  85. GRB 251126A: Swift/UVOT Detection
  86. EP251124a: Pan-STARRS ri-band imaging and photometry
  87. GRB 251126A: Mondy and SAO RAS optical observations
  88. GRB 251126A: Swift-XRT refined Analysis
  89. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  90. GRB 251126A: NOT optical observations
  91. GRB 251126A: 1.3m DFOT optical afterglow detection
  92. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  93. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  94. GRB 251125B: GECAM-B detection
  95. Fermi GRB 251127A: Global MASTER-Net observations report
  96. GRB 251127A: Fermi GBM Final Real-time Localization
  97. GRB 251126A: Enhanced Swift-XRT position
  98. GRB 251126A: Kilonova-Catcher optical afterglow detection
  99. GRB 251126A: Asiago i-band detection
  100. GRB 251126A: Nanshan/HMT optical afterglow detection

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