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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"

26324 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  2. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  3. GRB 251126A: SAO RAS optical marginal detection
  4. GRB 251202A: Swift-XRT afterglow detection
  5. EP251129a/GRB 251129A: NOWT Detection
  6. GRB 251126A: SVOM/VT optical observation
  7. EP251130a: SVOM/VT optical observation
  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. GRB 251201A: SVOM/GRM observation of a burst
  13. GRB 251201B: SVOM/VT optical fading
  14. Swift GRB 251201B : MASTER optical counterpart detection
  15. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  16. Swift GRB 251201B: Global MASTER-Net observations report
  17. GRB 251201B: Enhanced Swift-XRT position
  18. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  19. GRB 251201B: Swift detection of a burst with an optical counterpart
  20. GRB 251201B: Fermi GBM Final Real-time Localization
  21. EP251130a: Mondy optical observations
  22. EP251130a: Optical detections with Kinder observations
  23. SVOM GRB251201.19: Global MASTER-Net observations report
  24. EP251130a: SAO RAS optical observations
  25. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  26. EP251130A: Optical observation from 1.3m DFOT
  27. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  28. EP251130a: JinShan optical observations
  29. GRB 251201A: MAXI/GSC detection
  30. Fermi GRB 251130B: Global MASTER-Net observations report
  31. GRB 251127A: SVOM/GRM observation
  32. IceCube Alert 251130.75: Global MASTER-Net observations report
  33. EP251130a: Swift-XRT counterpart detection
  34. EP251130a: Global MASTER-Net observations report
  35. EP251130a: COLIBRÍ optical counterpart candidate
  36. EP251130a: Einstein Probe detection of an X-ray transient
  37. GRB 251129A / EP251129a: SAO RAS optical observations
  38. GRB 251126A: SAO RAS optical observations
  39. GRB 251128A: SVOM/GRM observation of a long burst
  40. SVOM GRB 251129A : MASTER optical counterpart detection
  41. GRB 251129A: Swift-XRT afterglow detection
  42. EP251129a: Global MASTER-Net observations report
  43. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  44. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  45. GRB 251128A: Fermi GBM Observation
  46. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  47. GRB 251129A: SVOM detection of a burst
  48. SVOM GRB251129A: Global MASTER-Net observations report
  49. GRB 251129A: SVOM detection of a burst
  50. GRB 251126A: Swift-BAT refined analysis
  51. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  52. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  53. Fermi GRB 251128A: Global MASTER-Net observations report
  54. GRB 251127A: Glowbug gamma-ray detection
  55. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  56. GRB 251126A: further SAO RAS optical observations
  57. GRB 251126A NUTTelA-TAO Early Measurements
  58. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  59. GRB251126A: MAO/AZT-22 optical observations
  60. GRB251126A: Continued optical observation from 1.3m DFOT
  61. GRB 251126A: Swift/UVOT Detection
  62. GRB 251126A: Mondy and SAO RAS optical observations
  63. GRB 251126A: Swift-XRT refined Analysis
  64. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  65. GRB 251126A: NOT optical observations
  66. GRB 251126A: 1.3m DFOT optical afterglow detection
  67. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  68. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  69. Fermi GRB 251127A: Global MASTER-Net observations report
  70. GRB 251126A: Enhanced Swift-XRT position
  71. GRB 251126A: Kilonova-Catcher optical afterglow detection
  72. GRB 251126A: Nanshan/HMT optical afterglow detection
  73. Swift GRB 251126A: Global MASTER-Net observations report
  74. GRB 251121A: Fermi GBM Observation
  75. GRB 251126A: GIT discovery of the likely optical afterglow
  76. GRB 251126A: Swift detection of a burst
  77. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  78. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  79. EP251124b: NOT r- and z-band optical upper limits
  80. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  81. Fermi GRB 251125B: Global MASTER-Net observations report
  82. EP251124b: Global MASTER-Net observations report
  83. EP251124b: EP-WXT detection of a fast X-ray transient
  84. EP251124a: Xinglong GWAC-F60A optical observation
  85. Fermi GRB 251125A: Global MASTER-Net observations report
  86. EP251124a: NOT r- and z-band optical upper limits
  87. EP251124a: Global MASTER-Net observations report
  88. EP251124a: Swift-XRT observations
  89. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  90. EP251124a: Optical upper limit with Kinder observations
  91. Fermi GRB 251124a: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  93. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  94. EP251124a: GROWTH-India Telescope optical upper limits
  95. EP251124a: Einstein Probe detection of an X-ray transient
  96. GRB 251116C: Swift-XRT confirmation of fading
  97. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  98. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  99. EP251118A: 3.6m DOT optical afterglow detection
  100. GRB 251122A / EP251122a: EP-FXT counterpart detection

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