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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 251201B: Swift-XRT refined Analysis
  2. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  3. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  4. GRB 251202A: Fermi GBM Final Real-time Localization
  5. GRB 251201A: SVOM/GRM observation of a burst
  6. GRB 251201B: SVOM/VT optical fading
  7. Swift GRB 251201B : MASTER optical counterpart detection
  8. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  9. Swift GRB 251201B: Global MASTER-Net observations report
  10. GRB 251201B: Enhanced Swift-XRT position
  11. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  12. GRB 251130B: AstroSat CZTI detection
  13. GRB 251201B: Swift detection of a burst with an optical counterpart
  14. GRB 251201B: Fermi GBM Final Real-time Localization
  15. EP251130a: Mondy optical observations
  16. EP251130a: Optical detections with Kinder observations
  17. SVOM GRB251201.19: Global MASTER-Net observations report
  18. EP251130a: SAO RAS optical observations
  19. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  20. EP251130a: KAIT optical observations
  21. EP251130A: Optical observation from 1.3m DFOT
  22. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  23. EP251130a: JinShan optical observations
  24. GRB 251201A: MAXI/GSC detection
  25. Fermi GRB 251130B: Global MASTER-Net observations report
  26. GRB 251127A: SVOM/GRM observation
  27. IceCube Alert 251130.75: Global MASTER-Net observations report
  28. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  29. EP251130a: Swift-XRT counterpart detection
  30. GRB 251130B: Fermi GBM Final Localization Correction
  31. EP251130a: Global MASTER-Net observations report
  32. GRB 251130B: Fermi GBM Final Real-time Localization
  33. EP251130a: COLIBRÍ optical counterpart candidate
  34. EP251130a: Einstein Probe detection of an X-ray transient
  35. EP251129a/GRB 251129A: EP-FXT follow-up observations
  36. GRB 251130A: Fermi GBM Final Real-time Localization
  37. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  38. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  39. GRB 251128A: AstroSat CZTI detection
  40. GRB 251129A / EP251129a: SAO RAS optical observations
  41. GRB 251126A: SAO RAS optical observations
  42. GRB 251128A: GECAM-B detection
  43. GRB 251128A: SVOM/GRM observation of a long burst
  44. GRB 251128A: Insight-HXMT/HE detection
  45. SVOM GRB 251129A : MASTER optical counterpart detection
  46. GRB 251129A: Swift-XRT afterglow detection
  47. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  48. Swift trigger 1418333 is not an astrophysical source
  49. GRB 251129A: Swift ToO observations
  50. GRB 251129A / EP251129a: SVOM/VT optical fading
  51. EP251129a: Global MASTER-Net observations report
  52. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  53. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  54. GRB 251129A: Correction to the position of the optical counterpar
  55. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  56. GRB 251128A: Fermi GBM Observation
  57. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  58. GRB 251129A: SVOM detection of a burst
  59. SVOM GRB251129A: Global MASTER-Net observations report
  60. GRB 251129A: SVOM detection of a burst
  61. GRB 251126A: Swift-BAT refined analysis
  62. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  63. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  64. Fermi GRB 251128A: Global MASTER-Net observations report
  65. GRB 251127A: Glowbug gamma-ray detection
  66. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  67. GRB 251126A: further SAO RAS optical observations
  68. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  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. GRB 251128A: Fermi GBM Final Real-time Localization
  73. GRB251126A: Continued optical observation from 1.3m DFOT
  74. GRB 251126A: Swift/UVOT Detection
  75. EP251124a: Pan-STARRS ri-band imaging and photometry
  76. GRB 251126A: Mondy and SAO RAS optical observations
  77. GRB 251126A: Swift-XRT refined Analysis
  78. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  79. GRB 251126A: NOT optical observations
  80. GRB 251126A: 1.3m DFOT optical afterglow detection
  81. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  82. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  83. GRB 251125B: GECAM-B detection
  84. Fermi GRB 251127A: Global MASTER-Net observations report
  85. GRB 251127A: Fermi GBM Final Real-time Localization
  86. GRB 251126A: Enhanced Swift-XRT position
  87. GRB 251126A: Kilonova-Catcher optical afterglow detection
  88. GRB 251126A: Asiago i-band detection
  89. GRB 251126A: Nanshan/HMT optical afterglow detection
  90. Swift GRB 251126A: Global MASTER-Net observations report
  91. GRB 251121A: Fermi GBM Observation
  92. GRB 251126A: Prompt enhanced Swift-XRT position
  93. GRB 251126A: GIT discovery of the likely optical afterglow
  94. GRB 251126A: Swift detection of a burst
  95. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  96. EP251124b follow-up observation by EP-FXT
  97. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  98. EP251124b: NOT r- and z-band optical upper limits
  99. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  100. Fermi GRB 251125B: Global MASTER-Net observations report

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