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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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.

Advanced Search Examples (click to copy):

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

42849 results found.

  1. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  2. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  3. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  4. GRB 260419A: AstroSat CZTI detection
  5. GRB 260421B: SVOM/GRM observation
  6. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  7. GRB 260421B: EP-FXT follow-up observation
  8. The EP-WXT trigger 01709260362 is likely a flaring star
  9. GOTO26djh/AT2026jpw: ATCA radio detection
  10. GRB 260421B: J-band upper limit with WINTER
  11. GRB 260421B: LCO optical counterpart detection
  12. GRB 260421B: Fermi GBM Observation
  13. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  14. GRB 260421A: AstroSat CZTI detection
  15. GOTO26djh/AT2026jpw: radio detection at 15GHz
  16. GRB 260412A: SVOM/ECLAIRs refined analysis
  17. GRB 260421B: SVOM/VT optical observations
  18. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  19. GRB 260310A: Late-time Chandra X-ray Detection
  20. GRB 260418A: Insight-HXMT/HE detection
  21. EP260416a: 1.3m DFOT optical observation
  22. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  23. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  24. Fermi GRB 260421C: Global MASTER-Net observations report
  25. GRB 260421C: Fermi GBM Final Real-time Localization
  26. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  27. Fermi GRB 260421B: Global MASTER-Net observations report
  28. GRB 260421B: BOOTES-7 early optical afterglow detection
  29. GRB 260421B: LCO optical afterglow confirmation
  30. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  31. GRB 260421B: TRT optical counterpart detection
  32. GRB 260421B: SVOM detection of a long burst
  33. GRB 260421B: Fermi GBM Final Real-time Localization
  34. Fermi GRB 260421A: Global MASTER-Net observations report
  35. GRB 260421A: Fermi GBM Final Real-time Localization
  36. EP260321a: VLA radio follow-up
  37. GRB 260412A: LCOGT Optical Upper Limits
  38. The EP-WXT trigger 01709260314 is likely a flaring star
  39. EP260416a: Optical follow-up observations with Kinder
  40. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  41. EP-WXT trigger 01709260303: KAIT optical observations
  42. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  43. The EP-WXT trigger 01709260303 is likely a flaring star
  44. GRB 260417A: SVOM/GRM observation
  45. GRB 260419B: Fermi GBM Final Real-time Localization
  46. GRB 260419A: Fermi GBM Final Real-time Localization
  47. Fermi trigger No 798275385: Global MASTER-Net observations report
  48. EP260417a: GROWTH-India Telescope optical upper limit
  49. Fermi GRB 260417B: Global MASTER-Net observations report
  50. EP260417b: GROWTH-India Telescope optical upper limit
  51. EP260416a: Ondrejov D50 optical detection
  52. GRB 260418B: Fermi GBM Final Real-time Localization
  53. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  54. EP260417a: Global MASTER-Net observations report
  55. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  56. GRB 260418A: Fermi GBM Final Real-time Localization
  57. EP260416a: GMG Optical Observation
  58. Fermi GRB 260417A: Global MASTER-Net observations report
  59. Konus-Wind detection of GRB 260411B
  60. GRB 260417B: Fermi GBM Final Real-time Localization
  61. GRB 260417A: AstroSat CZTI detection
  62. IPN triangulation of GRB 260411B
  63. EP260416a: LCO observations confirm end of flaring phase
  64. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  65. EP260417a: TRT optical counterpart detection
  66. EP260417a: Einstein Probe detection of an X-ray transient
  67. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  68. EP260417b: Einstein Probe detection of a fast X-ray transient
  69. EP-WXT trigger 01709259586: KAIT optical observations
  70. EP260416a: KAIT optical upper limit
  71. GRB 260414A: Insight-HXMT/HE detection
  72. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  73. GRB 260417A: Fermi GBM Final Real-time Localization
  74. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  75. EP260416a: SVOM/VT optical observation
  76. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  77. GRB 260415B: Glowbug gamma-ray detection
  78. GRB 260411B: Glowbug gamma-ray detection
  79. GRB 260415A: Insight-HXMT/HE detection
  80. EP260416a: COLIBRÍ optical counterpart candidate
  81. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  82. EP260416a: Global MASTER-Net observations report
  83. EP260416a: Einstein Probe detection of an X-ray transient
  84. GOTO26djh/AT2026jpw : MASTER OT observation
  85. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  86. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  87. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  88. GRB 260415B: NuSTAR detection of long prompt emission
  89. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  90. GRB 260415B: Fermi GBM Final Localization
  91. GRB 260415A: Fermi GBM Final Real-time Localization
  92. Fermi trigger No 797912738: Global MASTER-Net observations report
  93. GRB 260414A: Glowbug gamma-ray detection
  94. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  95. EP260321a: CMO SAI J,K observations
  96. GRB 260412A: Insight-HXMT/HE detection
  97. GRB 260414A: Fermi GBM Final Real-time Localization
  98. The EP-WXT trigger 01709260122 is likely a flaring star
  99. Fermi GRB 260413A: Global MASTER-Net observations report
  100. GRB 260410A: Glowbug gamma-ray detection of a short burst

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