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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. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  2. GRB 251202A: Fermi GBM Final Real-time Localization
  3. GRB 251201A: SVOM/GRM observation of a burst
  4. GRB 251201B: SVOM/VT optical fading
  5. Swift GRB 251201B : MASTER optical counterpart detection
  6. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  7. Swift GRB 251201B: Global MASTER-Net observations report
  8. GRB 251201B: Enhanced Swift-XRT position
  9. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  10. GRB 251130B: AstroSat CZTI detection
  11. GRB 251201B: Swift detection of a burst with an optical counterpart
  12. GRB 251201B: Fermi GBM Final Real-time Localization
  13. EP251130a: Mondy optical observations
  14. EP251130a: Optical detections with Kinder observations
  15. SVOM GRB251201.19: Global MASTER-Net observations report
  16. EP251130a: SAO RAS optical observations
  17. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  18. EP251130a: KAIT optical observations
  19. EP251130A: Optical observation from 1.3m DFOT
  20. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  21. EP251130a: JinShan optical observations
  22. GRB 251201A: MAXI/GSC detection
  23. Fermi GRB 251130B: Global MASTER-Net observations report
  24. GRB 251127A: SVOM/GRM observation
  25. IceCube Alert 251130.75: Global MASTER-Net observations report
  26. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  27. EP251130a: Swift-XRT counterpart detection
  28. GRB 251130B: Fermi GBM Final Localization Correction
  29. EP251130a: Global MASTER-Net observations report
  30. GRB 251130B: Fermi GBM Final Real-time Localization
  31. EP251130a: COLIBRÍ optical counterpart candidate
  32. EP251130a: Einstein Probe detection of an X-ray transient
  33. EP251129a/GRB 251129A: EP-FXT follow-up observations
  34. GRB 251130A: Fermi GBM Final Real-time Localization
  35. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  36. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  37. GRB 251128A: AstroSat CZTI detection
  38. GRB 251129A / EP251129a: SAO RAS optical observations
  39. GRB 251126A: SAO RAS optical observations
  40. GRB 251128A: GECAM-B detection
  41. GRB 251128A: SVOM/GRM observation of a long burst
  42. GRB 251128A: Insight-HXMT/HE detection
  43. SVOM GRB 251129A : MASTER optical counterpart detection
  44. GRB 251129A: Swift-XRT afterglow detection
  45. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  46. Swift trigger 1418333 is not an astrophysical source
  47. GRB 251129A: Swift ToO observations
  48. GRB 251129A / EP251129a: SVOM/VT optical fading
  49. EP251129a: Global MASTER-Net observations report
  50. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  51. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  52. GRB 251129A: Correction to the position of the optical counterpar
  53. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  54. GRB 251128A: Fermi GBM Observation
  55. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  56. GRB 251129A: SVOM detection of a burst
  57. SVOM GRB251129A: Global MASTER-Net observations report
  58. GRB 251129A: SVOM detection of a burst
  59. GRB 251126A: Swift-BAT refined analysis
  60. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  61. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  62. Fermi GRB 251128A: Global MASTER-Net observations report
  63. GRB 251127A: Glowbug gamma-ray detection
  64. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  65. GRB 251126A: further SAO RAS optical observations
  66. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  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. GRB 251128A: Fermi GBM Final Real-time Localization
  71. GRB251126A: Continued optical observation from 1.3m DFOT
  72. GRB 251126A: Swift/UVOT Detection
  73. EP251124a: Pan-STARRS ri-band imaging and photometry
  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. GRB 251125B: GECAM-B detection
  82. Fermi GRB 251127A: Global MASTER-Net observations report
  83. GRB 251127A: Fermi GBM Final Real-time Localization
  84. GRB 251126A: Enhanced Swift-XRT position
  85. GRB 251126A: Kilonova-Catcher optical afterglow detection
  86. GRB 251126A: Asiago i-band detection
  87. GRB 251126A: Nanshan/HMT optical afterglow detection
  88. Swift GRB 251126A: Global MASTER-Net observations report
  89. GRB 251121A: Fermi GBM Observation
  90. GRB 251126A: Prompt enhanced Swift-XRT position
  91. GRB 251126A: GIT discovery of the likely optical afterglow
  92. GRB 251126A: Swift detection of a burst
  93. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  94. EP251124b follow-up observation by EP-FXT
  95. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  96. EP251124b: NOT r- and z-band optical upper limits
  97. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  98. Fermi GRB 251125B: Global MASTER-Net observations report
  99. GRB 251125B: Fermi GBM Final Real-time Localization
  100. EP251124b: Global MASTER-Net observations report

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