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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"

16157 results found.

  1. EP260728a: COLIBRÍ optical upper limit
  2. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  3. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  4. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  5. EP260727a: SAO RAS optical observations
  6. GRB 260727A: AbAO and SAO RAS optical observations
  7. GRB 260726A: EP-FXT follow-up observations
  8. GRB 260727A: SVOM/GRM observation
  9. GRB 260726A: Fermi GBM Observation
  10. EP260727a: 1.5m OSN optical counterpart detection
  11. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  12. EP260727a: OHP/T193 optical observations
  13. GRB 260726A: Liverpool Telescope optical observations
  14. GRB 260727A: Liverpool Telescope optical upper limits
  15. EP260727a: Liverpool Telescope confirmation of optical counterpart
  16. EP260727a: NUTTELA-TAO Early Optical Limits
  17. GRB 260727A: EP/FXT follow-up observations
  18. EP260727a: Einstein Probe detection of an X-ray transient
  19. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  20. GRB 260726A: J-band upper limit with WINTER
  21. GRB 260726A: SVOM/VT optical candidate
  22. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  23. GRB 260727A: GOTO early optical upper limit
  24. GRB 260727A: Kilonova-Catcher optical upper limit
  25. GRB 260727A: LCO optical upper limits
  26. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  27. EP260723a: further EP-FXT follow-up observation
  28. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  29. EP260723a: EP-FXT follow-up observation
  30. EP260723a: SVOM/VT optical observation
  31. EP260723a: COLIBRÍ optical observations
  32. EP260723a: NOT optical conterpart confirmation
  33. EP260723a: Liverpool Telescope likely optical counterpart
  34. GRB 260705A: Retraction of optical counterpart
  35. GRB 260718A: LCO optical upper limits
  36. GRB 260710A: SVOM/GRM observation
  37. GRB 260718A : GRANDMA and KNC upper limits
  38. GRB 260718A: SVOM/VT optical upper limits
  39. GRB 260718A: SVOM/VT optical upper limits from VHF data
  40. GRB 260714B: SVOM/GRM observation
  41. GRB 260618B: EP-FXT follow-up observation upper limit
  42. GRB 260714B: COLIBRÍ optical counterpart candidate
  43. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  44. GRB 260705A: ATCA radio observations
  45. GRB 260619A: SVOM/VT continuous optical observations
  46. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  47. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  48. EP260623a: KAIT optical observations
  49. GRB 260708A: GRANDMA Optical Observations
  50. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  51. GRB 260708A: LCO optical observations
  52. GRB 260709A: SVOM/GRM detection
  53. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  54. GRB 260708A: Glowbug gamma-ray detection
  55. GRB 260706A : GRANDMA Upper limits
  56. GRB 260708A: Kilonova-Catcher optical afterglow detection
  57. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  58. GRB 260705B: SVOM/GRM observation
  59. GRB 260706A: SVOM/VT optical upper limits
  60. EP260707a (by EP-FXT): NOT optical upper limit
  61. EP260707a is not a real source
  62. EP260707a: LCOGT Optical Upper Limit
  63. EP260707a: TRT optical upper limit
  64. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  65. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  66. GRB 260706A: REM optical/NIR observations
  67. IceCube-260704A: No candidates from the Zwicky Transient Facility
  68. GRB 260706A: LCO optical upper limit
  69. GRB 260706A: SVOM detection of a burst
  70. IceCube260704A: OHP/T193 optical observations
  71. GRB 260705A: LCO optical upper limits
  72. GRB 260704A: NOT optical upper limits
  73. GRB 260705A: SVOM detection of a burst
  74. GRB 260629A: SVOM/GRM observation of a short burst
  75. GRB 260610B: VLA detection
  76. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  77. EP260626a: further Liverpool Telescope optical upper limits
  78. EP260626a: EP-FXT follow-up observation
  79. EP260626a: COLIBRÍ optical upper limit
  80. EP260623a: FTW optical and NIR observations
  81. EP260623a: Liverpool Telescope optical observations
  82. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  83. EP260623a: WINTER J-band observations
  84. EP260623a: Optical follow-up observations with Kinder
  85. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  86. EP260623a: SVOM/VT optical observations
  87. EP260623a: TRT optical observations
  88. EP260623a: REM optical/NIR afterglow detection
  89. EP 260623a: COLIBRÍ optical observations
  90. EP260623a: OSIRIS+/GTC redshift z = 0.703
  91. EP260623a: Las Cumbres discovery of the optical counterpart
  92. GRB 260614B: EP-FXT follow-up observation
  93. EP260618a: Liverpool Telescope optical observations
  94. GRB 260619A: NOT optical observations
  95. GRB 260618B: LCO optical observations
  96. EP260618a: JinShan optical observations
  97. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  98. GRB 260619A: TRT optical counterpart confirmation
  99. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  100. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening

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