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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"

16110 results found.

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

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