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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"

28094 results found.

  1. EP260416a: Mondy and Terskol optical upper limits
  2. GRB 260424B: Glowbug gamma-ray detection of a short burst
  3. GRB 260424B: COLIBRÍ optical upper limit
  4. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  5. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  6. IceCube Alert 260425A: Global MASTER-Net observations report
  7. Fermi trigger No 798737427: Global MASTER-Net observations report
  8. GRB 260401A: cubesat Avion detection
  9. EP260321a: Upper limits from ATCA radio observations
  10. GRB 260421B: Kilonova-Catcher optical afterglow detection
  11. The EP-WXT trigger 01709258652: Mondy optical observations
  12. EP260416a: Mondy optical observations
  13. GRB 260421B: 3.6m DOT optical observation
  14. EP260416a: ZTSh R band observations
  15. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 260421B: SVOM/GRM observation
  17. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  18. GRB 260421B: EP-FXT follow-up observation
  19. GOTO26djh/AT2026jpw: ATCA radio detection
  20. GRB 260421B: J-band upper limit with WINTER
  21. GRB 260421B: LCO optical counterpart detection
  22. GRB 260421B: Fermi GBM Observation
  23. GOTO26djh/AT2026jpw: radio detection at 15GHz
  24. GRB 260421B: SVOM/VT optical observations
  25. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  26. GRB 260310A: Late-time Chandra X-ray Detection
  27. EP260416a: 1.3m DFOT optical observation
  28. Fermi GRB 260421C: Global MASTER-Net observations report
  29. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  30. Fermi GRB 260421B: Global MASTER-Net observations report
  31. GRB 260421B: LCO optical afterglow confirmation
  32. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  33. GRB 260421B: TRT optical counterpart detection
  34. GRB 260421B: SVOM detection of a long burst
  35. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  36. Fermi GRB 260421A: Global MASTER-Net observations report
  37. EP260321a: VLA radio follow-up
  38. GRB 260412A: LCOGT Optical Upper Limits
  39. EP260416a: Optical follow-up observations with Kinder
  40. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  41. GRB 260417A: SVOM/GRM observation
  42. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  43. Fermi trigger No 798275385: Global MASTER-Net observations report
  44. EP260417a: GROWTH-India Telescope optical upper limit
  45. Fermi GRB 260417B: Global MASTER-Net observations report
  46. EP260417b: GROWTH-India Telescope optical upper limit
  47. EP260416a: Ondrejov D50 optical detection
  48. EP260417a: Global MASTER-Net observations report
  49. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  50. EP260416a: GMG Optical Observation
  51. Fermi GRB 260417A: Global MASTER-Net observations report
  52. EP260416a: LCO observations confirm end of flaring phase
  53. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  54. EP260417a: TRT optical counterpart detection
  55. EP260417a: Einstein Probe detection of an X-ray transient
  56. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  57. EP260417b: Einstein Probe detection of a fast X-ray transient
  58. EP260416a: KAIT optical upper limit
  59. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  60. EP260416a: WFST optical observations and rebrightening
  61. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  62. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  63. GRB 260415B: Glowbug gamma-ray detection
  64. GRB 260411B: Glowbug gamma-ray detection
  65. EP260416a: COLIBRÍ optical counterpart candidate
  66. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  67. EP260416a: Global MASTER-Net observations report
  68. EP260416a: Einstein Probe detection of an X-ray transient
  69. GOTO26djh/AT2026jpw : MASTER OT observation
  70. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  71. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  72. GRB 260415B: NuSTAR detection of long prompt emission
  73. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  74. Fermi trigger No 797912738: Global MASTER-Net observations report
  75. GRB 260414A: Glowbug gamma-ray detection
  76. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  77. EP260321a: CMO SAI J,K observations
  78. Fermi GRB 260413A: Global MASTER-Net observations report
  79. GRB 260410A: Glowbug gamma-ray detection of a short burst
  80. Fermi GRB 260412A: Global MASTER-Net observations report
  81. GRB 260412A: Fermi GBM Observation
  82. GRB 260411B: Fermi-LAT detection
  83. GRB 260411B: COLIBRÍ optical observations
  84. GRB 260410B: Fermi GBM Observation
  85. GRB260411B: 3.6m DOT optical observation
  86. GRB 260411A: SVOM/GRM observation
  87. GRB 260411B: SVOM/GRM observation of a long burst
  88. GRB 260409A: Insight-HXMT/HE detection
  89. GRB 260411B: Fermi GBM Detection
  90. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  91. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  92. GRB 260410A: COLIBRÍ optical upper limit
  93. EP-WXT01709259790: Optical Upper limits with kinder observations
  94. GRB 260410A: Fermi GBM Observation
  95. GRB 260410B: SVOM/GRM detection of a short faint burst
  96. EP-WXT01709259790: Xinglong optical upper limit
  97. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  98. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  99. EP260409a: COLIBRÍ optical upper limits
  100. EP260409a: Global MASTER-Net observations report

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