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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"

42601 results found.

  1. GRB 251201A: GECAM-B observation of a burst
  2. GRB 251126A: SAO RAS optical marginal detection
  3. GRB 251202A: Swift-XRT afterglow detection
  4. EP251129a/GRB 251129A: NOWT Detection
  5. GRB 251126A: SVOM/VT optical observation
  6. EP251130a: SVOM/VT optical observation
  7. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  8. Fermi GRB 251202A: Global MASTER-Net observations report
  9. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  10. GRB 251201B: Swift-XRT refined Analysis
  11. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  12. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  13. GRB 251202A: Fermi GBM Final Real-time Localization
  14. GRB 251201A: SVOM/GRM observation of a burst
  15. GRB 251201B: SVOM/VT optical fading
  16. Swift GRB 251201B : MASTER optical counterpart detection
  17. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  18. Swift GRB 251201B: Global MASTER-Net observations report
  19. GRB 251201B: Enhanced Swift-XRT position
  20. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  21. GRB 251130B: AstroSat CZTI detection
  22. GRB 251201B: Swift detection of a burst with an optical counterpart
  23. GRB 251201B: Fermi GBM Final Real-time Localization
  24. EP251130a: Mondy optical observations
  25. EP251130a: Optical detections with Kinder observations
  26. SVOM GRB251201.19: Global MASTER-Net observations report
  27. EP251130a: SAO RAS optical observations
  28. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  29. EP251130a: KAIT optical observations
  30. EP251130A: Optical observation from 1.3m DFOT
  31. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  32. EP251130a: JinShan optical observations
  33. GRB 251201A: MAXI/GSC detection
  34. Fermi GRB 251130B: Global MASTER-Net observations report
  35. GRB 251127A: SVOM/GRM observation
  36. IceCube Alert 251130.75: Global MASTER-Net observations report
  37. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  38. EP251130a: Swift-XRT counterpart detection
  39. GRB 251130B: Fermi GBM Final Localization Correction
  40. EP251130a: Global MASTER-Net observations report
  41. GRB 251130B: Fermi GBM Final Real-time Localization
  42. EP251130a: COLIBRÍ optical counterpart candidate
  43. EP251130a: Einstein Probe detection of an X-ray transient
  44. EP251129a/GRB 251129A: EP-FXT follow-up observations
  45. GRB 251130A: Fermi GBM Final Real-time Localization
  46. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  47. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  48. GRB 251128A: AstroSat CZTI detection
  49. GRB 251129A / EP251129a: SAO RAS optical observations
  50. GRB 251126A: SAO RAS optical observations
  51. GRB 251128A: GECAM-B detection
  52. GRB 251128A: SVOM/GRM observation of a long burst
  53. GRB 251128A: Insight-HXMT/HE detection
  54. SVOM GRB 251129A : MASTER optical counterpart detection
  55. GRB 251129A: Swift-XRT afterglow detection
  56. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  57. GRB 251129A: Swift ToO observations
  58. GRB 251129A / EP251129a: SVOM/VT optical fading
  59. EP251129a: Global MASTER-Net observations report
  60. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  61. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  62. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  63. GRB 251128A: Fermi GBM Observation
  64. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  65. GRB 251129A: SVOM detection of a burst
  66. SVOM GRB251129A: Global MASTER-Net observations report
  67. GRB 251129A: SVOM detection of a burst
  68. GRB 251126A: Swift-BAT refined analysis
  69. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  70. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  71. Fermi GRB 251128A: Global MASTER-Net observations report
  72. GRB 251127A: Glowbug gamma-ray detection
  73. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  74. GRB 251126A: further SAO RAS optical observations
  75. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  76. GRB 251126A NUTTelA-TAO Early Measurements
  77. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  78. GRB251126A: MAO/AZT-22 optical observations
  79. GRB 251128A: Fermi GBM Final Real-time Localization
  80. GRB251126A: Continued optical observation from 1.3m DFOT
  81. EP251124a: Pan-STARRS ri-band imaging and photometry
  82. GRB 251126A: Mondy and SAO RAS optical observations
  83. GRB 251126A: Swift-XRT refined Analysis
  84. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  85. GRB 251126A: NOT optical observations
  86. GRB 251126A: 1.3m DFOT optical afterglow detection
  87. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  88. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  89. GRB 251125B: GECAM-B detection
  90. Fermi GRB 251127A: Global MASTER-Net observations report
  91. GRB 251127A: Fermi GBM Final Real-time Localization
  92. GRB 251126A: Enhanced Swift-XRT position
  93. GRB 251126A: Kilonova-Catcher optical afterglow detection
  94. GRB 251126A: Asiago i-band detection
  95. GRB 251126A: Nanshan/HMT optical afterglow detection
  96. Swift GRB 251126A: Global MASTER-Net observations report
  97. GRB 251121A: Fermi GBM Observation
  98. GRB 251126A: Prompt enhanced Swift-XRT position
  99. GRB 251126A: GIT discovery of the likely optical afterglow
  100. GRB 251126A: Swift detection of a burst

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