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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"

42600 results found.

  1. GRB 260818B: LCO optical upper limits
  2. GRB 260818B: SVOM detection of a short burst
  3. EP260806a: SAO RAS multicolor optical observations
  4. GRB 260818A: LCO optical upper limits
  5. EP260812a: AbAO optical upper limit
  6. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. GRB 260810A: Insight-HXMT/HE detection
  8. GRB 260818A: SVOM possible detection of a long and faint GRB
  9. EP260806a: SVOM/ECLAIRs detection through targeted search
  10. EP260806a: NUTTELA-TAO optical observations
  11. The EP-WXT trigger 01709281429 is likely a flaring star
  12. EP260812a: AZT-22 optical upper limit
  13. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  14. EP260806a: WFST optical observations
  15. The EP-WXT trigger 01709280562 is likely a flaring star
  16. EP260812b: Optical upper limit with Kinder
  17. The EP-WXT trigger 01709279838 is likely a flaring star
  18. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  19. GRB 260808B: Liverpool Telescope further optical observations
  20. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  21. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  22. GRB 260813A: Fermi GBM Final Real-time Localization
  23. EP260812a: NOT and Liverpool Telescope upper limits:
  24. EP260812b: Liverpool Telescope observations
  25. EP260812b: GOTO detection of the optical counterpart
  26. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  27. EP260812a: SVOM/C-GFT optical upper limit
  28. EP260812b: COLIBRÍ optical observations
  29. EP260812b: SVOM/VT optical observation
  30. GRB 260808A: SVOM/GRM observation
  31. EP260812b: Einstein Probe detection of an X-ray transient
  32. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  33. Fermi GBM Sub-Threshold Detection of GRB 260809A
  34. GRB 260810A: Glowbug gamma-ray detection
  35. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  36. GRB 260810A: AstroSat CZTI detection of a long burst
  37. EP260812a: Einstein Probe detection of an X-ray transient
  38. GRB 260809A: SAO RAS optical observations
  39. GRB 260808B: SAO RAS optical observations
  40. GRB 260808B: SVOM/VT optical re-brightening at day 3
  41. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  42. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  43. GRB 260808A: GECAM-B observation
  44. GRB 260807A: SVOM/ECLAIRs refined analysis
  45. EP260806a: MAO/AZT-22 optical observations
  46. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB260808B: MAO/AZT-22 optical observations
  48. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  49. GRB 260809A: J-band upper limit with WINTER
  50. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  51. GRB 260806A: Glowbug gamma-ray detection
  52. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  53. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  54. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  55. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  56. The EP-WXT trigger 01709278015 is likely a flaring star
  57. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  58. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  59. GRB 260809A: NOT optical observations
  60. GRB260809A: MAO/AZT-22 optical observations
  61. GRB260809A: OHP/T193 optical observations
  62. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 260809A: SVOM/VT optical counterpart
  64. EP260809a: J-band upper limit with WINTER
  65. GRB 260808B: J-band upper limit with WINTER
  66. GRB 260808B: SVOM/ECLAIRs refined analysis
  67. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  68. GRB 260809A: SVOM detection of a faint burst
  69. GRB 260808B: Liverpool Telescope optical observations
  70. GRB 260808B: NOT optical observations
  71. GRB 260808B: LCO optical observations
  72. GRB 260808A: NuSTAR detection of prompt emission
  73. EP260809a: COLIBRÍ optical observations
  74. EP260809a: LCO optical observation
  75. EP260809a: OHP/T193 optical observations
  76. GRB260808B: OHP/T193 optical observations
  77. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  78. EP260809a: Einstein Probe detection of an X-ray transient
  79. GRB 260808B: SVOM/VT optical afterglow confirmation
  80. GRB 260808C: Fermi GBM Final Real-time Localization
  81. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  82. GRB 260808B: SVOM/VT optical candidate from VHF data
  83. GRB 260808B: SVOM detection of a faint burst
  84. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  85. Fermi GRB 260808A: Global MASTER-Net observations report
  86. GRB 260808A: Fermi GBM Final Real-time Localization
  87. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  88. IceCube Alert 260807A: Global MASTER-Net observations report
  89. IceCube-260805A: One candidate from the Zwicky Transient Facility
  90. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRB 260807A: SVOM possible detection of a faint burst
  92. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  93. EP260806a: COLIBRÍ optical observations
  94. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. EP260806a: SVOM/VT optical observation
  96. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  97. EP260806a: OSIRIS+/GTC redshift z=0.089
  98. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  99. EP260806a: LCO likely optical counterpart
  100. EP260806a: Einstein Probe detection of an X-ray transient

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