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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"

20350 results found.

  1. GRB260808B: MAO/AZT-22 optical observations
  2. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  3. GRB 260809A: J-band upper limit with WINTER
  4. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  5. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  7. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  8. GRB 260809A: NOT optical observations
  9. GRB260809A: MAO/AZT-22 optical observations
  10. GRB260809A: OHP/T193 optical observations
  11. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  12. EP260809a: J-band upper limit with WINTER
  13. GRB 260808B: J-band upper limit with WINTER
  14. GRB 260808B: SVOM/ECLAIRs refined analysis
  15. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  16. GRB 260809A: SVOM detection of a faint burst
  17. GRB 260808B: Liverpool Telescope optical observations
  18. GRB 260808B: NOT optical observations
  19. GRB 260808B: LCO optical observations
  20. EP260809a: COLIBRÍ optical observations
  21. EP260809a: LCO optical observation
  22. EP260809a: OHP/T193 optical observations
  23. GRB260808B: OHP/T193 optical observations
  24. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  25. EP260809a: Einstein Probe detection of an X-ray transient
  26. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  27. GRB 260808B: SVOM/VT optical candidate from VHF data
  28. GRB 260808B: SVOM detection of a faint burst
  29. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  30. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. EP260806a: COLIBRÍ optical observations
  32. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260806a: SVOM/VT optical observation
  34. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  35. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260806a: LCO likely optical counterpart
  37. EP260806a: Einstein Probe detection of an X-ray transient
  38. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  39. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 260804A: Fermi GBM Final Real-time Localization
  41. GRB 260802A: SVOM/VT optical upper limits from VHF data
  42. GRB 260802A: LCO optical upper limits
  43. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  45. GRB 260731A: AstroSat CZTI detection of a long burst
  46. EP260731a: COLIBRÍ optical upper limit
  47. EP260731a: NOT optical upper limit
  48. EP260731a: Einstein Probe detection of an X-ray transient
  49. GRB 260727A: SVOM/ECLAIRs refined analysis
  50. GRB 260726A: SVOM/ECLAIRs refined analysis
  51. EP260728a: COLIBRÍ optical upper limit
  52. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  53. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  54. EP260729a: Einstein Probe detection of an X-ray transient
  55. EP260727a: SAO RAS optical observations
  56. GRB 260727A: AbAO and SAO RAS optical observations
  57. EP260728a: EP-FXT follow-up observation
  58. EP260728a: Einstein Probe detection of a fast X-ray transient
  59. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  60. EP260727a: OHP/T193 optical observations
  61. GRB 260726A: Liverpool Telescope optical observations
  62. GRB 260727A: Liverpool Telescope optical upper limits
  63. EP260727a: Liverpool Telescope confirmation of optical counterpart
  64. EP260727a: Einstein Probe detection of an X-ray transient
  65. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  66. GRB 260726A: J-band upper limit with WINTER
  67. GRB 260727A: J-band upper limit with WINTER
  68. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  69. EP260723a: SVOM/ECLAIRs Upper Limit
  70. GRB 260727A: AstroSat CZTI detection
  71. GRB 260727A: Kilonova-Catcher optical upper limit
  72. GRB 260727A: LCO optical upper limits
  73. GRB 260726A: SVOM detection of a burst
  74. EP260725a: EP-WXT detection of an X-ray transient
  75. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  76. GRB 260601A: cubesat Avion detection
  77. GRB 260718A: SVOM/ECLAIRs refined analysis
  78. EP260723a: SVOM/VT optical observation
  79. EP260723a: COLIBRÍ optical observations
  80. EP260723a: NOT optical conterpart confirmation
  81. EP260723a: Liverpool Telescope likely optical counterpart
  82. EP260723a: EP-WXT detection of a fast X-ray transient
  83. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  84. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  85. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  86. GRB 260705A: Retraction of optical counterpart
  87. GRB 260718A: LCO optical upper limits
  88. GRB 260710A: SVOM/GRM observation
  89. GRB 260718A : GRANDMA and KNC upper limits
  90. GRB 260718A: SVOM/VT optical upper limits
  91. GRB 260718A: SVOM/VT optical upper limits from VHF data
  92. GRB 260714B: SVOM/GRM observation
  93. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  94. GRB 260714B: GECAM-B observation of a burst
  95. GRB 260714B: COLIBRÍ optical counterpart candidate
  96. sb26071506: SVOM detection of a X-ray transient
  97. EP260703a: SVOM/ECLAIRs Upper Limit
  98. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  99. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  100. GRB 260706A: ATCA detection of possible radio counterpart

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