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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"

27867 results found.

  1. EP260723a: further EP-FXT follow-up observation
  2. EP260725a: EP-WXT detection of an X-ray transient
  3. GRB 260616A: cubesat Avion detection
  4. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  5. GRB 260602B: cubesat Avion detection
  6. GRB 260601A: cubesat Avion detection
  7. EP260723a: SVOM/VT optical observation
  8. EP260723a: COLIBRÍ optical observations
  9. EP260723a: NOT optical conterpart confirmation
  10. EP260723a: Liverpool Telescope likely optical counterpart
  11. EP260723a: EP-WXT detection of a fast X-ray transient
  12. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  13. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  14. IceCube Alert 260722A: Global MASTER-Net observations report
  15. GRB 260721A: NuSTAR detection of prompt emission
  16. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  17. Fermi trigger No 806104130: Global MASTER-Net observations report
  18. Fermi GRB 260718A: Global MASTER-Net observations report
  19. GRB 260718A: LCO optical upper limits
  20. GRB 260710A: SVOM/GRM observation
  21. GRB 260718A: Fermi GBM Observation
  22. GRB 260718A : GRANDMA and KNC upper limits
  23. GRB 260718A: SVOM/VT optical upper limits
  24. GRB 260718A: SVOM/VT optical upper limits from VHF data
  25. GRB 260714B: SVOM/GRM observation
  26. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  27. GRB 260714B: COLIBRÍ optical counterpart candidate
  28. SVOM sb26071506: Global MASTER-Net observations report
  29. sb26071506: SVOM detection of a X-ray transient
  30. EP260703a: SVOM/ECLAIRs Upper Limit
  31. GRB 260710A: AstroSat CZTI detection
  32. GRB 260714B: Fermi GBM Detection
  33. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  34. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  35. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  36. EP260713a: Einstein Probe detection of an X-ray transient
  37. GRB 260619A: SVOM/VT continuous optical observations
  38. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  39. EP260623a: KAIT optical observations
  40. GRB 260708A: GRANDMA Optical Observations
  41. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  42. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  43. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  44. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 260708A: LCO optical observations
  46. EP260711a: Einstein Probe detection of an X-ray transient
  47. GRB 260709A: SVOM/GRM detection
  48. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  49. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  50. GRB 260708A: Glowbug gamma-ray detection
  51. GRB 260706A : GRANDMA Upper limits
  52. GRB 260708A: Kilonova-Catcher optical afterglow detection
  53. IceCube-260708A: One candidate from the Zwicky Transient Facility
  54. GRB 260708A: Fermi-GBM observation
  55. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  56. IceCube Alert 260709A: Global MASTER-Net observations report
  57. LAT GRB260708.42: Global MASTER-Net observations report
  58. GRB260708B: MAXI/GSC detection
  59. GRB 260705B: SVOM/GRM observation
  60. GRB 260706A: Further EP-FXT follow-up observation
  61. EP260707a (by EP-FXT): NOT optical upper limit
  62. EP260707a is not a real source
  63. EP260707a: LCOGT Optical Upper Limit
  64. EP260707a: TRT optical upper limit
  65. EP260707a: Einstein Probe detection of an X-ray transient
  66. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  67. GRB 260705C: Glowbug gamma-ray detection of a short burst
  68. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  69. GRB 260706A: REM optical/NIR observations
  70. GRB 260706A: LCO optical upper limit
  71. GRB 260706A: EP-FXT follow-up observation
  72. The EP-WXT trigger 01709274151 is likely a flaring star
  73. GRB 260706A: Fermi GBM Observation
  74. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 260706A: SVOM detection of a burst
  76. GRB 260705A: LCO optical upper limits
  77. GRB 260704A: NOT optical upper limits
  78. Fermi GBM Sub-Threshold Detection of GRB 260705A
  79. GRB 260704A: EP-FXT follow-up observation
  80. GRB 260629A: SVOM/GRM observation of a short burst
  81. GRB 260629A: AstroSat CZTI detection
  82. EP260703a: EP-FXT follow-up observation
  83. GRB 260704A: SVOM detection of a possible GRB
  84. EP260703a: EP-WXT detection of a fast X-ray transient
  85. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  86. Fermi trigger No 804738310: Global MASTER-Net observations report
  87. Fermi GRB 260703A: Global MASTER-Net observations report
  88. GRB 260623A: Glowbug gamma-ray detection
  89. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  90. Fermi trigger No 804552016: Global MASTER-Net observations report
  91. GRB 260701A: Fermi GBM Final Real-time Localization
  92. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  93. EP260628a: EP-FXT follow-up observation
  94. Fermi GRB 260628A: Global MASTER-Net observations report
  95. EP260628a: EP-WXT detection of a fast X-ray transient
  96. EP260626a: further Liverpool Telescope optical upper limits
  97. EP260626a: COLIBRÍ optical upper limit
  98. EP260626a: Liverpool Telescope upper limits
  99. EP260626a: EP-WXT detection of a fast X-ray transient
  100. EP260623a: TNG NIR afterglow detection

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