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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

18334 results found.

  1. EP260507a: Kinder optical counterpart candidate
  2. EP260507a: LCO optical counterpart
  3. EP260507a: Einstein Probe detection of an X-ray transient
  4. GRB 260504B: AstroSat CZTI detection
  5. EP260502a is likely a flaring star
  6. GRB 260421B: radio observation with the VLA
  7. GRB 260504B: EP-FXT upper limit
  8. GRB 260502A: SVOM/GRM observation of a short GRB
  9. GRB 260503A: SVOM/GRM observation of a GRB
  10. GRB 260504B: REM optical/NIR observations
  11. GRB 260504B: LCO z-band upper limit
  12. GRB 260504B: SVOM detection of a short burst
  13. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  14. The EP-WXT trigger 01709261576 is likely a flaring star
  15. GRB 260429B / EP260429a: EP-FXT follow-up observation
  16. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  17. GRB 260429B / EP260429a: AstroSat CZTI detection
  18. EP260502a: Einstein Probe detection of an X-ray transient
  19. GRB 260429A: SVOM/GRM observation of a short burst
  20. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  21. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  22. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  23. EP260429a: LCO optical upper limits
  24. EP260430a: LCO optical upper limits
  25. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  26. EP260430a: Einstein Probe detection of an X-ray transient
  27. EP260429a: EP-WXT detection of a fast X-ray transient
  28. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  29. EP260416a: Mondy and Terskol optical upper limits
  30. GRB 260424B: COLIBRÍ optical upper limit
  31. EP260321a: Upper limits from ATCA radio observations
  32. GRB 260421B: Kilonova-Catcher optical afterglow detection
  33. EP260416a: Mondy optical observations
  34. GRB 260421B: 3.6m DOT optical observation
  35. EP260416a: ZTSh R band observations
  36. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  37. GRB 260421B: SVOM/GRM observation
  38. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  39. GRB 260421B: EP-FXT follow-up observation
  40. The EP-WXT trigger 01709260362 is likely a flaring star
  41. GOTO26djh/AT2026jpw: ATCA radio detection
  42. GRB 260421B: J-band upper limit with WINTER
  43. GRB 260421B: LCO optical counterpart detection
  44. GRB 260421B: SVOM/VT optical observations
  45. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  46. GRB 260310A: Late-time Chandra X-ray Detection
  47. EP260416a: 1.3m DFOT optical observation
  48. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  49. GRB 260421B: LCO optical afterglow confirmation
  50. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  51. GRB 260421B: TRT optical counterpart detection
  52. GRB 260421B: SVOM detection of a long burst
  53. EP260321a: VLA radio follow-up
  54. GRB 260412A: LCOGT Optical Upper Limits
  55. The EP-WXT trigger 01709260314 is likely a flaring star
  56. EP260416a: Optical follow-up observations with Kinder
  57. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  58. The EP-WXT trigger 01709260303 is likely a flaring star
  59. GRB 260417A: SVOM/GRM observation
  60. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  61. EP260417a: GROWTH-India Telescope optical upper limit
  62. EP260417b: GROWTH-India Telescope optical upper limit
  63. EP260416a: Ondrejov D50 optical detection
  64. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  65. EP260416a: GMG Optical Observation
  66. EP260416a: LCO observations confirm end of flaring phase
  67. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  68. EP260417a: TRT optical counterpart detection
  69. EP260417a: Einstein Probe detection of an X-ray transient
  70. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  71. EP260417b: Einstein Probe detection of a fast X-ray transient
  72. EP260416a: KAIT optical upper limit
  73. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  74. EP260416a: WFST optical observations and rebrightening
  75. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  76. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  77. EP260416a: COLIBRÍ optical counterpart candidate
  78. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  79. EP260416a: Einstein Probe detection of an X-ray transient
  80. GOTO26djh/AT2026jpw : MASTER OT observation
  81. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  82. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  83. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  84. EP260321a: CMO SAI J,K observations
  85. The EP-WXT trigger 01709260122 is likely a flaring star
  86. The EP-WXT trigger 01709260010 is likely a flaring star
  87. GRB 260411B: Fermi-LAT detection
  88. GRB 260411B: COLIBRÍ optical observations
  89. GRB260411B: 3.6m DOT optical observation
  90. GRB 260411A: SVOM/GRM observation
  91. GRB 260411B: SVOM/GRM observation of a long burst
  92. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  93. GRB 260410A: COLIBRÍ optical upper limit
  94. EP-WXT01709259790: Optical Upper limits with kinder observations
  95. The EP-WXT trigger 01709259790 is likely a flaring star
  96. EP-WXT01709259790: Xinglong optical upper limit
  97. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  98. GRB 260409A: Fermi GBM Final Real-time Localization
  99. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  100. The EP-WXT trigger 01709259773 is likely a flaring star

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