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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"

26313 results found.

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

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