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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"

16112 results found.

  1. EP260812b: Liverpool Telescope observations
  2. EP260812b: GOTO detection of the optical counterpart
  3. EP260812a: SVOM/C-GFT optical upper limit
  4. EP260812b: COLIBRÍ optical observations
  5. EP260812b: SVOM/VT optical observation
  6. GRB 260808A: SVOM/GRM observation
  7. EP260812b: Einstein Probe detection of an X-ray transient
  8. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  9. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  10. GRB 260809A: SAO RAS optical observations
  11. GRB 260808B: SAO RAS optical observations
  12. GRB 260808B: SVOM/VT optical re-brightening at day 3
  13. EP260806a: MAO/AZT-22 optical observations
  14. GRB260808B: MAO/AZT-22 optical observations
  15. GRB 260809A: J-band upper limit with WINTER
  16. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  17. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  18. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  19. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  20. GRB 260809A: NOT optical observations
  21. GRB260809A: MAO/AZT-22 optical observations
  22. GRB260809A: OHP/T193 optical observations
  23. GRB 260809A: SVOM/VT optical counterpart
  24. EP260809a: J-band upper limit with WINTER
  25. GRB 260808B: J-band upper limit with WINTER
  26. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  27. GRB 260808B: Liverpool Telescope optical observations
  28. GRB 260808B: NOT optical observations
  29. GRB 260808B: LCO optical observations
  30. EP260809a: COLIBRÍ optical observations
  31. EP260809a: LCO optical observation
  32. EP260809a: OHP/T193 optical observations
  33. GRB260808B: OHP/T193 optical observations
  34. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  35. GRB 260808B: SVOM/VT optical afterglow confirmation
  36. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  37. GRB 260808B: SVOM/VT optical candidate from VHF data
  38. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  39. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB 260807A: SVOM possible detection of a faint burst
  41. EP260806a: COLIBRÍ optical observations
  42. EP260806a: SVOM/VT optical observation
  43. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  44. EP260806a: OSIRIS+/GTC redshift z=0.089
  45. EP260806a: LCO likely optical counterpart
  46. SN 2026stf / GRB 260708A: ATLAS forced photometry
  47. AT 2026wki: EP/FXT follow-up observations
  48. GRB 260708A: LCO further optical observations show supernova features
  49. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  50. GRB 260802A: SVOM/VT optical upper limits from VHF data
  51. GRB 260802A: LCO optical upper limits
  52. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  54. EP260731a: COLIBRÍ optical upper limit
  55. EP260731a: NOT optical upper limit
  56. EP260728a: COLIBRÍ optical upper limit
  57. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  58. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  59. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  60. EP260727a: SAO RAS optical observations
  61. GRB 260727A: AbAO and SAO RAS optical observations
  62. GRB 260726A: EP-FXT follow-up observations
  63. GRB 260727A: SVOM/GRM observation
  64. GRB 260726A: Fermi GBM Observation
  65. EP260727a: 1.5m OSN optical counterpart detection
  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: NUTTELA-TAO Early Optical Limits
  72. GRB 260727A: EP/FXT follow-up observations
  73. EP260727a: Einstein Probe detection of an X-ray transient
  74. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  75. GRB 260726A: J-band upper limit with WINTER
  76. GRB 260726A: SVOM/VT optical candidate
  77. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  78. GRB 260727A: GOTO early optical upper limit
  79. GRB 260727A: Kilonova-Catcher optical upper limit
  80. GRB 260727A: LCO optical upper limits
  81. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  82. EP260723a: further EP-FXT follow-up observation
  83. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  84. EP260723a: EP-FXT follow-up observation
  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. GRB 260705A: Retraction of optical counterpart
  90. GRB 260718A: LCO optical upper limits
  91. GRB 260710A: SVOM/GRM observation
  92. GRB 260718A : GRANDMA and KNC upper limits
  93. GRB 260718A: SVOM/VT optical upper limits
  94. GRB 260718A: SVOM/VT optical upper limits from VHF data
  95. GRB 260714B: SVOM/GRM observation
  96. GRB 260618B: EP-FXT follow-up observation upper limit
  97. GRB 260714B: COLIBRÍ optical counterpart candidate
  98. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  99. GRB 260705A: ATCA radio observations
  100. GRB 260619A: SVOM/VT continuous optical observations

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