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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"

26330 results found.

  1. GRB 251201B: Swift/UVOT Detection
  2. GRB 251130B: Glowbug gamma-ray detection
  3. EP251130a: continued NOT optical observations indicate steep fading phase
  4. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  5. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  6. GRB 251126A: SAO RAS optical marginal detection
  7. GRB 251202A: Swift-XRT afterglow detection
  8. EP251129a/GRB 251129A: NOWT Detection
  9. GRB 251126A: SVOM/VT optical observation
  10. EP251130a: SVOM/VT optical observation
  11. Fermi GRB 251202A: Global MASTER-Net observations report
  12. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  13. GRB 251201B: Swift-XRT refined Analysis
  14. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB 251201A: SVOM/GRM observation of a burst
  16. GRB 251201B: SVOM/VT optical fading
  17. Swift GRB 251201B : MASTER optical counterpart detection
  18. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  19. Swift GRB 251201B: Global MASTER-Net observations report
  20. GRB 251201B: Enhanced Swift-XRT position
  21. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  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: Optical observation from 1.3m DFOT
  30. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  31. EP251130a: JinShan optical observations
  32. GRB 251201A: MAXI/GSC detection
  33. Fermi GRB 251130B: Global MASTER-Net observations report
  34. GRB 251127A: SVOM/GRM observation
  35. IceCube Alert 251130.75: Global MASTER-Net observations report
  36. EP251130a: Swift-XRT counterpart detection
  37. EP251130a: Global MASTER-Net observations report
  38. EP251130a: COLIBRÍ optical counterpart candidate
  39. EP251130a: Einstein Probe detection of an X-ray transient
  40. GRB 251129A / EP251129a: SAO RAS optical observations
  41. GRB 251126A: SAO RAS optical observations
  42. GRB 251128A: SVOM/GRM observation of a long burst
  43. SVOM GRB 251129A : MASTER optical counterpart detection
  44. GRB 251129A: Swift-XRT afterglow detection
  45. EP251129a: Global MASTER-Net observations report
  46. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  47. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  48. GRB 251128A: Fermi GBM Observation
  49. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  50. GRB 251129A: SVOM detection of a burst
  51. SVOM GRB251129A: Global MASTER-Net observations report
  52. GRB 251129A: SVOM detection of a burst
  53. GRB 251126A: Swift-BAT refined analysis
  54. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  55. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  56. Fermi GRB 251128A: Global MASTER-Net observations report
  57. GRB 251127A: Glowbug gamma-ray detection
  58. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  59. GRB 251126A: further SAO RAS optical observations
  60. GRB 251126A NUTTelA-TAO Early Measurements
  61. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  62. GRB251126A: MAO/AZT-22 optical observations
  63. GRB251126A: Continued optical observation from 1.3m DFOT
  64. GRB 251126A: Swift/UVOT Detection
  65. GRB 251126A: Mondy and SAO RAS optical observations
  66. GRB 251126A: Swift-XRT refined Analysis
  67. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  68. GRB 251126A: NOT optical observations
  69. GRB 251126A: 1.3m DFOT optical afterglow detection
  70. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  71. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  72. Fermi GRB 251127A: Global MASTER-Net observations report
  73. GRB 251126A: Enhanced Swift-XRT position
  74. GRB 251126A: Kilonova-Catcher optical afterglow detection
  75. GRB 251126A: Nanshan/HMT optical afterglow detection
  76. Swift GRB 251126A: Global MASTER-Net observations report
  77. GRB 251121A: Fermi GBM Observation
  78. GRB 251126A: GIT discovery of the likely optical afterglow
  79. GRB 251126A: Swift detection of a burst
  80. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  81. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  82. EP251124b: NOT r- and z-band optical upper limits
  83. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  84. Fermi GRB 251125B: Global MASTER-Net observations report
  85. EP251124b: Global MASTER-Net observations report
  86. EP251124b: EP-WXT detection of a fast X-ray transient
  87. EP251124a: Xinglong GWAC-F60A optical observation
  88. Fermi GRB 251125A: Global MASTER-Net observations report
  89. EP251124a: NOT r- and z-band optical upper limits
  90. EP251124a: Global MASTER-Net observations report
  91. EP251124a: Swift-XRT observations
  92. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  93. EP251124a: Optical upper limit with Kinder observations
  94. Fermi GRB 251124a: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  96. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  97. EP251124a: GROWTH-India Telescope optical upper limits
  98. EP251124a: Einstein Probe detection of an X-ray transient
  99. GRB 251116C: Swift-XRT confirmation of fading
  100. GRB 251122A/EP251122A: 1.3m DFOT optical detection

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