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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"

27182 results found.

  1. EP260416a: ZTSh R band observations
  2. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 260421B: SVOM/GRM observation
  4. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  5. GRB 260421B: EP-FXT follow-up observation
  6. GOTO26djh/AT2026jpw: ATCA radio detection
  7. GRB 260421B: J-band upper limit with WINTER
  8. GRB 260421B: LCO optical counterpart detection
  9. GRB 260421B: Fermi GBM Observation
  10. GOTO26djh/AT2026jpw: radio detection at 15GHz
  11. GRB 260421B: SVOM/VT optical observations
  12. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  13. GRB 260310A: Late-time Chandra X-ray Detection
  14. EP260416a: 1.3m DFOT optical observation
  15. Fermi GRB 260421C: Global MASTER-Net observations report
  16. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  17. Fermi GRB 260421B: Global MASTER-Net observations report
  18. GRB 260421B: LCO optical afterglow confirmation
  19. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  20. GRB 260421B: TRT optical counterpart detection
  21. GRB 260421B: SVOM detection of a long burst
  22. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  23. Fermi GRB 260421A: Global MASTER-Net observations report
  24. EP260321a: VLA radio follow-up
  25. GRB 260412A: LCOGT Optical Upper Limits
  26. EP260416a: Optical follow-up observations with Kinder
  27. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  28. GRB 260417A: SVOM/GRM observation
  29. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  30. Fermi trigger No 798275385: Global MASTER-Net observations report
  31. EP260417a: GROWTH-India Telescope optical upper limit
  32. Fermi GRB 260417B: Global MASTER-Net observations report
  33. EP260417b: GROWTH-India Telescope optical upper limit
  34. EP260416a: Ondrejov D50 optical detection
  35. EP260417a: Global MASTER-Net observations report
  36. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  37. EP260416a: GMG Optical Observation
  38. Fermi GRB 260417A: Global MASTER-Net observations report
  39. EP260416a: LCO observations confirm end of flaring phase
  40. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  41. EP260417a: TRT optical counterpart detection
  42. EP260417a: Einstein Probe detection of an X-ray transient
  43. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  44. EP260417b: Einstein Probe detection of a fast X-ray transient
  45. EP260416a: KAIT optical upper limit
  46. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  47. EP260416a: WFST optical observations and rebrightening
  48. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  49. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  50. GRB 260415B: Glowbug gamma-ray detection
  51. GRB 260411B: Glowbug gamma-ray detection
  52. EP260416a: COLIBRÍ optical counterpart candidate
  53. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  54. EP260416a: Global MASTER-Net observations report
  55. EP260416a: Einstein Probe detection of an X-ray transient
  56. GOTO26djh/AT2026jpw : MASTER OT observation
  57. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  58. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  59. GRB 260415B: NuSTAR detection of long prompt emission
  60. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  61. Fermi trigger No 797912738: Global MASTER-Net observations report
  62. GRB 260414A: Glowbug gamma-ray detection
  63. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  64. EP260321a: CMO SAI J,K observations
  65. Fermi GRB 260413A: Global MASTER-Net observations report
  66. GRB 260410A: Glowbug gamma-ray detection of a short burst
  67. Fermi GRB 260412A: Global MASTER-Net observations report
  68. GRB 260412A: Fermi GBM Observation
  69. GRB 260411B: Fermi-LAT detection
  70. GRB 260411B: COLIBRÍ optical observations
  71. GRB 260410B: Fermi GBM Observation
  72. GRB260411B: 3.6m DOT optical observation
  73. GRB 260411A: SVOM/GRM observation
  74. GRB 260411B: SVOM/GRM observation of a long burst
  75. GRB 260409A: Insight-HXMT/HE detection
  76. GRB 260411B: Fermi GBM Detection
  77. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  78. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  79. GRB 260410A: COLIBRÍ optical upper limit
  80. EP-WXT01709259790: Optical Upper limits with kinder observations
  81. GRB 260410A: Fermi GBM Observation
  82. GRB 260410B: SVOM/GRM detection of a short faint burst
  83. EP-WXT01709259790: Xinglong optical upper limit
  84. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  85. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  86. EP260409a: COLIBRÍ optical upper limits
  87. EP260409a: Global MASTER-Net observations report
  88. EP260409a: Einstein Probe detection of an X-ray transient
  89. EP260321a: VLA radio detection
  90. GRB 260407A: Glowbug gamma-ray detection
  91. GRB 260402A: SVOM/ECLAIRs refined analysis
  92. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  93. EP260402a / GRB 260402A: Mephisto optical upper limits
  94. EP-WXT01709259586: Xinglong optical upper limit
  95. EP260403a: Mephisto optical upper limits
  96. EP260402a/GRB 260402A: Xinglong optical upper limit
  97. EP260405a: GMOS-N optical upper limits
  98. EP260405a: Global MASTER-Net observations report
  99. EP260405a: Einstein Probe detection of a fast X-ray transient
  100. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits

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