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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"

27189 results found.

  1. Fermi trigger No 798737427: Global MASTER-Net observations report
  2. GRB 260401A: cubesat Avion detection
  3. EP260321a: Upper limits from ATCA radio observations
  4. GRB 260421B: Kilonova-Catcher optical afterglow detection
  5. The EP-WXT trigger 01709258652: Mondy optical observations
  6. EP260416a: Mondy optical observations
  7. GRB 260421B: 3.6m DOT optical observation
  8. EP260416a: ZTSh R band observations
  9. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 260421B: SVOM/GRM observation
  11. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  12. GRB 260421B: EP-FXT follow-up observation
  13. GOTO26djh/AT2026jpw: ATCA radio detection
  14. GRB 260421B: J-band upper limit with WINTER
  15. GRB 260421B: LCO optical counterpart detection
  16. GRB 260421B: Fermi GBM Observation
  17. GOTO26djh/AT2026jpw: radio detection at 15GHz
  18. GRB 260421B: SVOM/VT optical observations
  19. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  20. GRB 260310A: Late-time Chandra X-ray Detection
  21. EP260416a: 1.3m DFOT optical observation
  22. Fermi GRB 260421C: Global MASTER-Net observations report
  23. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  24. Fermi GRB 260421B: Global MASTER-Net observations report
  25. GRB 260421B: LCO optical afterglow confirmation
  26. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  27. GRB 260421B: TRT optical counterpart detection
  28. GRB 260421B: SVOM detection of a long burst
  29. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  30. Fermi GRB 260421A: Global MASTER-Net observations report
  31. EP260321a: VLA radio follow-up
  32. GRB 260412A: LCOGT Optical Upper Limits
  33. EP260416a: Optical follow-up observations with Kinder
  34. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  35. GRB 260417A: SVOM/GRM observation
  36. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  37. Fermi trigger No 798275385: Global MASTER-Net observations report
  38. EP260417a: GROWTH-India Telescope optical upper limit
  39. Fermi GRB 260417B: Global MASTER-Net observations report
  40. EP260417b: GROWTH-India Telescope optical upper limit
  41. EP260416a: Ondrejov D50 optical detection
  42. EP260417a: Global MASTER-Net observations report
  43. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  44. EP260416a: GMG Optical Observation
  45. Fermi GRB 260417A: Global MASTER-Net observations report
  46. EP260416a: LCO observations confirm end of flaring phase
  47. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  48. EP260417a: TRT optical counterpart detection
  49. EP260417a: Einstein Probe detection of an X-ray transient
  50. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. EP260417b: Einstein Probe detection of a fast X-ray transient
  52. EP260416a: KAIT optical upper limit
  53. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  54. EP260416a: WFST optical observations and rebrightening
  55. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  56. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  57. GRB 260415B: Glowbug gamma-ray detection
  58. GRB 260411B: Glowbug gamma-ray detection
  59. EP260416a: COLIBRÍ optical counterpart candidate
  60. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  61. EP260416a: Global MASTER-Net observations report
  62. EP260416a: Einstein Probe detection of an X-ray transient
  63. GOTO26djh/AT2026jpw : MASTER OT observation
  64. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  65. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  66. GRB 260415B: NuSTAR detection of long prompt emission
  67. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  68. Fermi trigger No 797912738: Global MASTER-Net observations report
  69. GRB 260414A: Glowbug gamma-ray detection
  70. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  71. EP260321a: CMO SAI J,K observations
  72. Fermi GRB 260413A: Global MASTER-Net observations report
  73. GRB 260410A: Glowbug gamma-ray detection of a short burst
  74. Fermi GRB 260412A: Global MASTER-Net observations report
  75. GRB 260412A: Fermi GBM Observation
  76. GRB 260411B: Fermi-LAT detection
  77. GRB 260411B: COLIBRÍ optical observations
  78. GRB 260410B: Fermi GBM Observation
  79. GRB260411B: 3.6m DOT optical observation
  80. GRB 260411A: SVOM/GRM observation
  81. GRB 260411B: SVOM/GRM observation of a long burst
  82. GRB 260409A: Insight-HXMT/HE detection
  83. GRB 260411B: Fermi GBM Detection
  84. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  85. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  86. GRB 260410A: COLIBRÍ optical upper limit
  87. EP-WXT01709259790: Optical Upper limits with kinder observations
  88. GRB 260410A: Fermi GBM Observation
  89. GRB 260410B: SVOM/GRM detection of a short faint burst
  90. EP-WXT01709259790: Xinglong optical upper limit
  91. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  92. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  93. EP260409a: COLIBRÍ optical upper limits
  94. EP260409a: Global MASTER-Net observations report
  95. EP260409a: Einstein Probe detection of an X-ray transient
  96. EP260321a: VLA radio detection
  97. GRB 260407A: Glowbug gamma-ray detection
  98. GRB 260402A: SVOM/ECLAIRs refined analysis
  99. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  100. EP260402a / GRB 260402A: Mephisto optical upper limits

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