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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"

26246 results found.

  1. GRB 251203B: Swift-XRT observations
  2. GRB 251203C: LCO optical upper limits
  3. GRB 251203B: LCO optical upper limits
  4. GRB 251203B: SVOM/VT optical observation
  5. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  6. SVOM GRB251203.77: Global MASTER-Net observations report
  7. SVOM GRB251203.76: Global MASTER-Net observations report
  8. GRB 251203B: SVOM detection of a burst
  9. EP251130a: MAO/AZT-22 optical observations
  10. GRB 251201B: Fermi GBM Observation
  11. EP251202a/GRB 251202A: KAIT optical observations
  12. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  13. Fermi GRB 251202B: Global MASTER-Net observations report
  14. IPN triangulation of GRB 251129B (short/hard)
  15. GRB251129A/EP251129a: Swift UVOT detection
  16. GRB 251202A: Fermi GBM Observation
  17. GRB 251202A: Swift/UVOT Detection
  18. GRB 251201B: Kilonova-Catcher optical afterglow detection
  19. GRB 251201B: Swift/UVOT Detection
  20. GRB 251130B: Glowbug gamma-ray detection
  21. EP251130a: continued NOT optical observations indicate steep fading phase
  22. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  23. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  24. GRB 251126A: SAO RAS optical marginal detection
  25. GRB 251202A: Swift-XRT afterglow detection
  26. EP251129a/GRB 251129A: NOWT Detection
  27. GRB 251126A: SVOM/VT optical observation
  28. EP251130a: SVOM/VT optical observation
  29. Fermi GRB 251202A: Global MASTER-Net observations report
  30. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  31. GRB 251201B: Swift-XRT refined Analysis
  32. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  33. GRB 251201A: SVOM/GRM observation of a burst
  34. GRB 251201B: SVOM/VT optical fading
  35. Swift GRB 251201B : MASTER optical counterpart detection
  36. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  37. Swift GRB 251201B: Global MASTER-Net observations report
  38. GRB 251201B: Enhanced Swift-XRT position
  39. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  40. GRB 251201B: Swift detection of a burst with an optical counterpart
  41. GRB 251201B: Fermi GBM Final Real-time Localization
  42. EP251130a: Mondy optical observations
  43. EP251130a: Optical detections with Kinder observations
  44. SVOM GRB251201.19: Global MASTER-Net observations report
  45. EP251130a: SAO RAS optical observations
  46. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  47. EP251130A: Optical observation from 1.3m DFOT
  48. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  49. EP251130a: JinShan optical observations
  50. GRB 251201A: MAXI/GSC detection
  51. Fermi GRB 251130B: Global MASTER-Net observations report
  52. GRB 251127A: SVOM/GRM observation
  53. IceCube Alert 251130.75: Global MASTER-Net observations report
  54. EP251130a: Swift-XRT counterpart detection
  55. EP251130a: Global MASTER-Net observations report
  56. EP251130a: COLIBRÍ optical counterpart candidate
  57. EP251130a: Einstein Probe detection of an X-ray transient
  58. GRB 251129A / EP251129a: SAO RAS optical observations
  59. GRB 251126A: SAO RAS optical observations
  60. GRB 251128A: SVOM/GRM observation of a long burst
  61. SVOM GRB 251129A : MASTER optical counterpart detection
  62. GRB 251129A: Swift-XRT afterglow detection
  63. EP251129a: Global MASTER-Net observations report
  64. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  65. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  66. GRB 251128A: Fermi GBM Observation
  67. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  68. GRB 251129A: SVOM detection of a burst
  69. SVOM GRB251129A: Global MASTER-Net observations report
  70. GRB 251129A: SVOM detection of a burst
  71. GRB 251126A: Swift-BAT refined analysis
  72. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  73. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  74. Fermi GRB 251128A: Global MASTER-Net observations report
  75. GRB 251127A: Glowbug gamma-ray detection
  76. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  77. GRB 251126A: further SAO RAS optical observations
  78. GRB 251126A NUTTelA-TAO Early Measurements
  79. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  80. GRB251126A: MAO/AZT-22 optical observations
  81. GRB251126A: Continued optical observation from 1.3m DFOT
  82. GRB 251126A: Swift/UVOT Detection
  83. GRB 251126A: Mondy and SAO RAS optical observations
  84. GRB 251126A: Swift-XRT refined Analysis
  85. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  86. GRB 251126A: NOT optical observations
  87. GRB 251126A: 1.3m DFOT optical afterglow detection
  88. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  89. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  90. Fermi GRB 251127A: Global MASTER-Net observations report
  91. GRB 251126A: Enhanced Swift-XRT position
  92. GRB 251126A: Kilonova-Catcher optical afterglow detection
  93. GRB 251126A: Nanshan/HMT optical afterglow detection
  94. Swift GRB 251126A: Global MASTER-Net observations report
  95. GRB 251121A: Fermi GBM Observation
  96. GRB 251126A: GIT discovery of the likely optical afterglow
  97. GRB 251126A: Swift detection of a burst
  98. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  99. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  100. EP251124b: NOT r- and z-band optical upper limits

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