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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"

27322 results found.

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

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