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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"

20357 results found.

  1. EP260812a: Einstein Probe detection of an X-ray transient
  2. GRB 260809A: SAO RAS optical observations
  3. GRB 260808B: SAO RAS optical observations
  4. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  5. GRB 260807A: SVOM/ECLAIRs refined analysis
  6. EP260806a: MAO/AZT-22 optical observations
  7. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB260808B: MAO/AZT-22 optical observations
  9. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  10. GRB 260809A: J-band upper limit with WINTER
  11. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  12. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  14. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  15. GRB 260809A: NOT optical observations
  16. GRB260809A: MAO/AZT-22 optical observations
  17. GRB260809A: OHP/T193 optical observations
  18. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  19. EP260809a: J-band upper limit with WINTER
  20. GRB 260808B: J-band upper limit with WINTER
  21. GRB 260808B: SVOM/ECLAIRs refined analysis
  22. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  23. GRB 260809A: SVOM detection of a faint burst
  24. GRB 260808B: Liverpool Telescope optical observations
  25. GRB 260808B: NOT optical observations
  26. GRB 260808B: LCO optical observations
  27. EP260809a: COLIBRÍ optical observations
  28. EP260809a: LCO optical observation
  29. EP260809a: OHP/T193 optical observations
  30. GRB260808B: OHP/T193 optical observations
  31. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  32. EP260809a: Einstein Probe detection of an X-ray transient
  33. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  34. GRB 260808B: SVOM/VT optical candidate from VHF data
  35. GRB 260808B: SVOM detection of a faint burst
  36. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  37. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. EP260806a: COLIBRÍ optical observations
  39. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  40. EP260806a: SVOM/VT optical observation
  41. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  42. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  43. EP260806a: LCO likely optical counterpart
  44. EP260806a: Einstein Probe detection of an X-ray transient
  45. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  46. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 260804A: Fermi GBM Final Real-time Localization
  48. GRB 260802A: SVOM/VT optical upper limits from VHF data
  49. GRB 260802A: LCO optical upper limits
  50. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  52. GRB 260731A: AstroSat CZTI detection of a long burst
  53. EP260731a: COLIBRÍ optical upper limit
  54. EP260731a: NOT optical upper limit
  55. EP260731a: Einstein Probe detection of an X-ray transient
  56. GRB 260727A: SVOM/ECLAIRs refined analysis
  57. GRB 260726A: SVOM/ECLAIRs refined analysis
  58. EP260728a: COLIBRÍ optical upper limit
  59. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  60. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  61. EP260729a: Einstein Probe detection of an X-ray transient
  62. EP260727a: SAO RAS optical observations
  63. GRB 260727A: AbAO and SAO RAS optical observations
  64. EP260728a: EP-FXT follow-up observation
  65. EP260728a: Einstein Probe detection of a fast X-ray transient
  66. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  67. EP260727a: OHP/T193 optical observations
  68. GRB 260726A: Liverpool Telescope optical observations
  69. GRB 260727A: Liverpool Telescope optical upper limits
  70. EP260727a: Liverpool Telescope confirmation of optical counterpart
  71. EP260727a: Einstein Probe detection of an X-ray transient
  72. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  73. GRB 260726A: J-band upper limit with WINTER
  74. GRB 260727A: J-band upper limit with WINTER
  75. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  76. EP260723a: SVOM/ECLAIRs Upper Limit
  77. GRB 260727A: AstroSat CZTI detection
  78. GRB 260727A: Kilonova-Catcher optical upper limit
  79. GRB 260727A: LCO optical upper limits
  80. GRB 260726A: SVOM detection of a burst
  81. EP260725a: EP-WXT detection of an X-ray transient
  82. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  83. GRB 260601A: cubesat Avion detection
  84. GRB 260718A: SVOM/ECLAIRs refined analysis
  85. EP260723a: SVOM/VT optical observation
  86. EP260723a: COLIBRÍ optical observations
  87. EP260723a: NOT optical conterpart confirmation
  88. EP260723a: Liverpool Telescope likely optical counterpart
  89. EP260723a: EP-WXT detection of a fast X-ray transient
  90. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  91. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  92. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  93. GRB 260705A: Retraction of optical counterpart
  94. GRB 260718A: LCO optical upper limits
  95. GRB 260710A: SVOM/GRM observation
  96. GRB 260718A : GRANDMA and KNC upper limits
  97. GRB 260718A: SVOM/VT optical upper limits
  98. GRB 260718A: SVOM/VT optical upper limits from VHF data
  99. GRB 260714B: SVOM/GRM observation
  100. GRB 260310A / AT2026fgk: Late-time Chandra Detection

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