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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"
  1. GRB 260818A: J-band observations with WINTER
  2. GRB 260818B: SVOM/ECLAIRs refined analysis
  3. GRB 260818A: SVOM/ECLAIRs refined analysis
  4. GRB 260818B: NOT optical upper limits
  5. GRB 260810A: SVOM/GRM observation
  6. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. GRB260818A: EP-FXT follow-up observation
  8. GRB 260818B: LCO optical upper limits
  9. GRB 260818B: SVOM detection of a short burst
  10. SVOM trigger sb26081806 is not a GRB
  11. EP260806a: SAO RAS multicolor optical observations
  12. GRB 260818A: LCO optical upper limits
  13. EP260812a: AbAO optical upper limit
  14. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. GRB 260810A: Insight-HXMT/HE detection
  16. GRB 260818A: SVOM possible detection of a long and faint GRB
  17. EP260806a: SVOM/ECLAIRs detection through targeted search
  18. EP260806a: NUTTELA-TAO optical observations
  19. The EP-WXT trigger 01709281429 is likely a flaring star
  20. EP260812a: AZT-22 optical upper limit
  21. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  22. EP260806a: WFST optical observations
  23. The EP-WXT trigger 01709280562 is likely a flaring star
  24. EP260812b: Optical upper limit with Kinder
  25. The EP-WXT trigger 01709279838 is likely a flaring star
  26. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  27. GRB 260808B: Liverpool Telescope further optical observations
  28. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  29. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  30. GRB 260813A: Fermi GBM Final Real-time Localization
  31. EP260812a: NOT and Liverpool Telescope upper limits:
  32. EP260812b: Liverpool Telescope observations
  33. EP260812b: GOTO detection of the optical counterpart
  34. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  35. EP260812a: SVOM/C-GFT optical upper limit
  36. EP260812b: COLIBRÍ optical observations
  37. EP260812b: SVOM/VT optical observation
  38. GRB 260808A: SVOM/GRM observation
  39. EP260812b: Einstein Probe detection of an X-ray transient
  40. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  41. Fermi GBM Sub-Threshold Detection of GRB 260809A
  42. GRB 260810A: Glowbug gamma-ray detection
  43. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  44. GRB 260810A: AstroSat CZTI detection of a long burst
  45. EP260812a: Einstein Probe detection of an X-ray transient
  46. GRB 260809A: SAO RAS optical observations
  47. GRB 260808B: SAO RAS optical observations
  48. GRB 260808B: SVOM/VT optical re-brightening at day 3
  49. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  50. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  51. GRB 260808A: GECAM-B observation
  52. GRB 260807A: SVOM/ECLAIRs refined analysis
  53. EP260806a: MAO/AZT-22 optical observations
  54. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB260808B: MAO/AZT-22 optical observations
  56. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  57. GRB 260809A: J-band upper limit with WINTER
  58. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  59. GRB 260806A: Glowbug gamma-ray detection
  60. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  63. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  64. The EP-WXT trigger 01709278015 is likely a flaring star
  65. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  66. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  67. GRB 260809A: NOT optical observations
  68. GRB260809A: MAO/AZT-22 optical observations
  69. GRB260809A: OHP/T193 optical observations
  70. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  71. GRB 260809A: SVOM/VT optical counterpart
  72. EP260809a: J-band upper limit with WINTER
  73. GRB 260808B: J-band upper limit with WINTER
  74. GRB 260808B: SVOM/ECLAIRs refined analysis
  75. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  76. GRB 260809A: SVOM detection of a faint burst
  77. GRB 260808B: Liverpool Telescope optical observations
  78. GRB 260808B: NOT optical observations
  79. GRB 260808B: LCO optical observations
  80. GRB 260808A: NuSTAR detection of prompt emission
  81. EP260809a: COLIBRÍ optical observations
  82. EP260809a: LCO optical observation
  83. EP260809a: OHP/T193 optical observations
  84. GRB260808B: OHP/T193 optical observations
  85. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  86. EP260809a: Einstein Probe detection of an X-ray transient
  87. GRB 260808B: SVOM/VT optical afterglow confirmation
  88. GRB 260808C: Fermi GBM Final Real-time Localization
  89. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  90. GRB 260808B: SVOM/VT optical candidate from VHF data
  91. GRB 260808B: SVOM detection of a faint burst
  92. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  93. Fermi GRB 260808A: Global MASTER-Net observations report
  94. GRB 260808A: Fermi GBM Final Real-time Localization
  95. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  96. IceCube Alert 260807A: Global MASTER-Net observations report
  97. IceCube-260805A: One candidate from the Zwicky Transient Facility
  98. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  99. GRB 260807A: SVOM possible detection of a faint burst
  100. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event

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