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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"

27319 results found.

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

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