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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').
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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"

26037 results found.

  1. EP260623a: TNG NIR afterglow detection
  2. GRB 260618A: Fermi GBM Observation
  3. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  4. EP260623a: REM optical/NIR afterglow detection
  5. EP260623a: OSIRIS+/GTC redshift z = 0.703
  6. GRB 260619A: NOT optical observations
  7. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  8. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  9. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  10. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  11. EP260618a: LCO optical counterpart confirmation
  12. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  13. EP260618a: EP-WXT detection of an X-ray transient
  14. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  15. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  16. GRB 260614B: SVOM/VT optical afterglow confirmation
  17. GRB 260610B / AT2026owq: GRANDMA optical observations
  18. GRB 260610B: IAC-80 Optical observations
  19. GRB 260610B: DDOTI optical observations
  20. GRB 260604C: SVOM/ECLAIRs refined analysis
  21. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  22. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  23. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  24. GRB 260604C: GRANDMA observations
  25. GRB 260604C: GOTO detections of the optical afterglow
  26. GRB 260604C: Kilonova-Catcher optical afterglow detection
  27. GRB 260604C: LAST detection of optical counterpart candidate
  28. GRB 260603A: NOT optical observations
  29. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  30. EP260602a: COLIBRÍ optical observations
  31. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  32. AT2026nik: EP-FXT X-ray counterpart
  33. AT 2026nuz: COLIBRÍ optical observations
  34. GRB 260527A / EP260527a: VLA radio detection
  35. GRB 260529A: GOTO tentative optical afterglow candidate
  36. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  37. EP260527a / GRB 260527A: NOT optical observations
  38. GRB 260527A/EP260527a: FTW optical and NIR observations
  39. GRB 260511A: iTelescope T-75 optical detection
  40. GRB 260516D: GOTO optical counterpart detection
  41. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  42. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  43. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  44. GRB 260515A: NOT optical observations.
  45. GRB 260515A: SVOM/VT optical candidate from VHF data
  46. GRB 260511B: NOT optical observations
  47. GRB 260509A: SVOM/VT optical observations
  48. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  49. GRB 260511B: FRAM-ORM optical detection
  50. GRB 260511B: LCO optical counterpart detection
  51. GRB 260511A: SVOM/VT optical observations
  52. GRB 260511B: SVOM/VT optical observations
  53. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  54. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  55. GRB 260511A: UTGO H50 optical afterglow observation
  56. GRB 260511A: KAIT optical afterglow observations
  57. GRB 260511A: LCO optical afterglow detection
  58. GRB 260509A: KAIT optical observations
  59. EP260507a: NOT optical observations
  60. EP260507a: TRT optical counterpart detection
  61. GRB 260504B: SVOM/MXT refined analysis and potential detection
  62. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  63. GRB 260429B / EP260429a: EP-FXT follow-up observation
  64. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  65. GRB 260421B: Kilonova-Catcher optical afterglow detection
  66. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  67. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  68. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  69. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  70. GRB 260310A: Late-time Chandra X-ray Detection
  71. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  72. GRB 260421B: BOOTES-7 early optical afterglow detection
  73. GRB 260421B: LCO optical afterglow confirmation
  74. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  75. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  76. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  77. EP260416a: Ondrejov D50 optical detection
  78. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  79. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  80. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  81. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  82. GRB 260411B: COLIBRÍ optical observations
  83. GRB 260411B: Ondrejov D50 optical afterglow detection
  84. GRB 260411B: SVOM/GRM observation of a long burst
  85. EP260321a: Chandra X-ray Non-detection
  86. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  87. GRB 260310A / AT2026fgk: X-ray rebrightening
  88. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  89. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  90. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  91. GRB 260321A: SVOM/ECLAIRs refined analysis
  92. GRB 260310A: VLA Multi-frequency Radio Observations
  93. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  94. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  95. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  96. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  97. GRB 260310A / AT 2026fgk: KAIT optical observations
  98. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  99. GRB 260310A / AT 2026fgk: iTelescope optical observations
  100. GRB 260310A/AT2026fgk: radio detection at 15GHz

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