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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"

42607 results found.

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

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