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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"

26314 results found.

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

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