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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"

15982 results found.

  1. SN 2026stf / GRB 260708A: ATLAS forced photometry
  2. AT 2026wki: EP/FXT follow-up observations
  3. GRB 260708A: LCO further optical observations show supernova features
  4. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  5. GRB 260802A: SVOM/VT optical upper limits from VHF data
  6. GRB 260802A: LCO optical upper limits
  7. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  9. EP260731a: COLIBRÍ optical upper limit
  10. EP260731a: NOT optical upper limit
  11. EP260728a: COLIBRÍ optical upper limit
  12. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  13. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  14. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  15. EP260727a: SAO RAS optical observations
  16. GRB 260727A: AbAO and SAO RAS optical observations
  17. GRB 260726A: EP-FXT follow-up observations
  18. GRB 260727A: SVOM/GRM observation
  19. GRB 260726A: Fermi GBM Observation
  20. EP260727a: 1.5m OSN optical counterpart detection
  21. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  22. EP260727a: OHP/T193 optical observations
  23. GRB 260726A: Liverpool Telescope optical observations
  24. GRB 260727A: Liverpool Telescope optical upper limits
  25. EP260727a: Liverpool Telescope confirmation of optical counterpart
  26. EP260727a: NUTTELA-TAO Early Optical Limits
  27. GRB 260727A: EP/FXT follow-up observations
  28. EP260727a: Einstein Probe detection of an X-ray transient
  29. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  30. GRB 260726A: J-band upper limit with WINTER
  31. GRB 260726A: SVOM/VT optical candidate
  32. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  33. GRB 260727A: GOTO early optical upper limit
  34. GRB 260727A: Kilonova-Catcher optical upper limit
  35. GRB 260727A: LCO optical upper limits
  36. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  37. EP260723a: further EP-FXT follow-up observation
  38. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  39. EP260723a: EP-FXT follow-up observation
  40. EP260723a: SVOM/VT optical observation
  41. EP260723a: COLIBRÍ optical observations
  42. EP260723a: NOT optical conterpart confirmation
  43. EP260723a: Liverpool Telescope likely optical counterpart
  44. GRB 260705A: Retraction of optical counterpart
  45. GRB 260718A: LCO optical upper limits
  46. GRB 260710A: SVOM/GRM observation
  47. GRB 260718A : GRANDMA and KNC upper limits
  48. GRB 260718A: SVOM/VT optical upper limits
  49. GRB 260718A: SVOM/VT optical upper limits from VHF data
  50. GRB 260714B: SVOM/GRM observation
  51. GRB 260618B: EP-FXT follow-up observation upper limit
  52. GRB 260714B: COLIBRÍ optical counterpart candidate
  53. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  54. GRB 260705A: ATCA radio observations
  55. GRB 260619A: SVOM/VT continuous optical observations
  56. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  57. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  58. EP260623a: KAIT optical observations
  59. GRB 260708A: GRANDMA Optical Observations
  60. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  61. GRB 260708A: LCO optical observations
  62. GRB 260709A: SVOM/GRM detection
  63. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  64. GRB 260708A: Glowbug gamma-ray detection
  65. GRB 260706A : GRANDMA Upper limits
  66. GRB 260708A: Kilonova-Catcher optical afterglow detection
  67. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  68. GRB 260705B: SVOM/GRM observation
  69. GRB 260706A: SVOM/VT optical upper limits
  70. EP260707a (by EP-FXT): NOT optical upper limit
  71. EP260707a is not a real source
  72. EP260707a: LCOGT Optical Upper Limit
  73. EP260707a: TRT optical upper limit
  74. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  75. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  76. GRB 260706A: REM optical/NIR observations
  77. IceCube-260704A: No candidates from the Zwicky Transient Facility
  78. GRB 260706A: LCO optical upper limit
  79. GRB 260706A: SVOM detection of a burst
  80. IceCube260704A: OHP/T193 optical observations
  81. GRB 260705A: LCO optical upper limits
  82. GRB 260704A: NOT optical upper limits
  83. GRB 260705A: SVOM detection of a burst
  84. GRB 260629A: SVOM/GRM observation of a short burst
  85. GRB 260610B: VLA detection
  86. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  87. EP260626a: further Liverpool Telescope optical upper limits
  88. EP260626a: EP-FXT follow-up observation
  89. EP260626a: COLIBRÍ optical upper limit
  90. EP260623a: FTW optical and NIR observations
  91. EP260623a: Liverpool Telescope optical observations
  92. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  93. EP260623a: WINTER J-band observations
  94. EP260623a: Optical follow-up observations with Kinder
  95. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  96. EP260623a: SVOM/VT optical observations
  97. EP260623a: TRT optical observations
  98. EP260623a: REM optical/NIR afterglow detection
  99. EP 260623a: COLIBRÍ optical observations
  100. EP260623a: OSIRIS+/GTC redshift z = 0.703

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