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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"

27705 results found.

  1. Fermi GRB 260802B: Global MASTER-Net observations report
  2. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  3. GRB 260802A: SVOM/VT optical upper limits from VHF data
  4. GRB 260802A: LCO optical upper limits
  5. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  7. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  8. EP260731a: COLIBRÍ optical upper limit
  9. EP260731a: NOT optical upper limit
  10. GRB 260730B: NuSTAR detection of prompt emission
  11. EP260731a: Einstein Probe detection of an X-ray transient
  12. EP260728a: COLIBRÍ optical upper limit
  13. EP260729a: Einstein Probe detection of an X-ray transient
  14. EP260727a: SAO RAS optical observations
  15. GRB 260727A: AbAO and SAO RAS optical observations
  16. EP260728a: EP-FXT follow-up observation
  17. GRB 260726A: EP-FXT follow-up observations
  18. EP260728a: Einstein Probe detection of a fast X-ray transient
  19. GRB 260726A: Fermi GBM Observation
  20. EP260727a: 1.5m OSN optical counterpart detection
  21. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  22. EP260727a: OHP/T193 optical observations
  23. GRB 260726A: Liverpool Telescope optical observations
  24. GRB 260727A: Liverpool Telescope optical upper limits
  25. EP260727a: Liverpool Telescope confirmation of optical counterpart
  26. EP260727a: Einstein Probe detection of an X-ray transient
  27. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  28. GRB 260727A: Glowbug gamma-ray detection
  29. GRB 260726A: J-band upper limit with WINTER
  30. GRB 260727A: J-band upper limit with WINTER
  31. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  32. EP260723a: SVOM/ECLAIRs Upper Limit
  33. GRB 260727A: AstroSat CZTI detection
  34. GRB 260727A: Kilonova-Catcher optical upper limit
  35. GRB 260727A: LCO optical upper limits
  36. Fermi GRB 260726A: Global MASTER-Net observations report
  37. GRB 260726A: SVOM detection of a burst
  38. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  39. EP260723a: further EP-FXT follow-up observation
  40. EP260725a: EP-WXT detection of an X-ray transient
  41. GRB 260616A: cubesat Avion detection
  42. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  43. GRB 260602B: cubesat Avion detection
  44. GRB 260601A: cubesat Avion detection
  45. EP260723a: SVOM/VT optical observation
  46. EP260723a: COLIBRÍ optical observations
  47. EP260723a: NOT optical conterpart confirmation
  48. EP260723a: Liverpool Telescope likely optical counterpart
  49. EP260723a: EP-WXT detection of a fast X-ray transient
  50. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  51. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  52. IceCube Alert 260722A: Global MASTER-Net observations report
  53. GRB 260721A: NuSTAR detection of prompt emission
  54. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  55. Fermi trigger No 806104130: Global MASTER-Net observations report
  56. Fermi GRB 260718A: Global MASTER-Net observations report
  57. GRB 260718A: LCO optical upper limits
  58. GRB 260710A: SVOM/GRM observation
  59. GRB 260718A: Fermi GBM Observation
  60. GRB 260718A : GRANDMA and KNC upper limits
  61. GRB 260718A: SVOM/VT optical upper limits
  62. GRB 260718A: SVOM/VT optical upper limits from VHF data
  63. GRB 260714B: SVOM/GRM observation
  64. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  65. GRB 260714B: COLIBRÍ optical counterpart candidate
  66. SVOM sb26071506: Global MASTER-Net observations report
  67. sb26071506: SVOM detection of a X-ray transient
  68. EP260703a: SVOM/ECLAIRs Upper Limit
  69. GRB 260710A: AstroSat CZTI detection
  70. GRB 260714B: Fermi GBM Detection
  71. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  72. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  73. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  74. EP260713a: Einstein Probe detection of an X-ray transient
  75. GRB 260619A: SVOM/VT continuous optical observations
  76. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  77. EP260623a: KAIT optical observations
  78. GRB 260708A: GRANDMA Optical Observations
  79. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  80. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  81. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  82. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 260708A: LCO optical observations
  84. EP260711a: Einstein Probe detection of an X-ray transient
  85. GRB 260709A: SVOM/GRM detection
  86. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  87. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  88. GRB 260708A: Glowbug gamma-ray detection
  89. GRB 260706A : GRANDMA Upper limits
  90. GRB 260708A: Kilonova-Catcher optical afterglow detection
  91. IceCube-260708A: One candidate from the Zwicky Transient Facility
  92. GRB 260708A: Fermi-GBM observation
  93. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  94. IceCube Alert 260709A: Global MASTER-Net observations report
  95. LAT GRB260708.42: Global MASTER-Net observations report
  96. GRB260708B: MAXI/GSC detection
  97. GRB 260705B: SVOM/GRM observation
  98. GRB 260706A: Further EP-FXT follow-up observation
  99. EP260707a (by EP-FXT): NOT optical upper limit
  100. EP260707a is not a real source

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