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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"

2767 results found.

  1. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  2. GRB 260619A: SVOM possible detection of a faint burst
  3. Konus-Wind detection of GRB 260616A
  4. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  5. GRB260616C: MAXI/GSC detection
  6. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  7. GRB 260610B / AT2026owq: SVOM/VT optical observations
  8. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  9. GRB 260610B / AT2026owq: Early ATLAS observations
  10. GRB 260604C: GRANDMA further observations
  11. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  12. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  13. EP260602a: COLIBRÍ optical observations
  14. GRB 260601B/EP260601a: Insight-HXMT detection
  15. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  16. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  17. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  18. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  19. GRB 260527A/EP260527a: FTW optical and NIR observations
  20. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  21. GRB 260516D: GOTO optical counterpart detection
  22. GRB 260516D: GROWTH-India Telescope optical detection
  23. GRB 260516D: SVOM possible detection of a burst
  24. EP260507a: Kinder optical counterpart candidate
  25. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  26. GRB 260504B: SVOM detection of a short burst
  27. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  28. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  29. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  30. GRB 260411B: COLIBRÍ optical observations
  31. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  32. EP260321a: uGMRT observations
  33. EP260329a: EP-FXT follow up observation
  34. EP260321a: Upper limits from a neutrino search with IceCube
  35. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  36. EP260321a: further Kinder optical observations
  37. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  38. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  39. EP260314a: COLIBRÍ optical upper limit
  40. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  41. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  42. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  43. GRB 260307B: possible NOT optical counterpart
  44. GRB 260207A: TESS Detection and Possible VLA Counterpart
  45. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  46. GRB 260303A: SVOM detection of a burst
  47. EP260214a: VLA 6 GHz detection
  48. GRB 260204A: SVOM/ECLAIRs refined analysis
  49. EP260128a: Liverpool Telescope optical observations and possible counterpart
  50. GRB 251208D: SVOM/ECLAIRs refined analysis
  51. GRB 251208D: SVOM/ECLAIRs refined analysis
  52. GRB 260109C: LCO optical upper limits
  53. Swift Trigger 1434591: possible GRB 260109C
  54. GRB 260103A: SVOM/GRM observation of a possible GRB
  55. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  56. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  57. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  59. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  60. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  61. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  62. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  63. GRB 251208D: SVOM possible detection of a faint burst
  64. Swift GRB 251205A : MASTER OT detection with host galaxy
  65. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  66. GRB 251203B: LCO optical upper limits
  67. GRB 251201A: GECAM-B observation of a burst
  68. GRB 251201A: SVOM/GRM observation of a burst
  69. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  70. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  71. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  72. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  73. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  74. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  75. GRB 251116D: SVOM/GRM observation of a long GRB
  76. GRB 251119A: SVOM detection of a possible burst
  77. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  78. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  79. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  80. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  81. Swift Trigger 1413695: a possible GRB 251112A
  82. IPN triangulation of GRB 251105B (possible sGRB with EE)
  83. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  84. Konus-Wind detection of GRB 251028A
  85. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  86. GRB 251026B: Tentative GOTO optical counterpart candidate
  87. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  88. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  89. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  90. Swift Trigger 1404295: possible GRB 251015A
  91. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  92. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  93. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  94. GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission
  95. IceCube alert 141456_888784 retraction
  96. GRB 251006A (short): Glowbug gamma-ray detection
  97. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  98. GRB 251001B: COLIBRÍ optical observations
  99. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  100. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM

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