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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.

Advanced Search Examples (click to copy):

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

44470 results found.

  1. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  2. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  3. GRB 260419A: AstroSat CZTI detection
  4. GRB 260421B: SVOM/GRM observation
  5. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  6. GRB 260421B: EP-FXT follow-up observation
  7. The EP-WXT trigger 01709260362 is likely a flaring star
  8. GOTO26djh/AT2026jpw: ATCA radio detection
  9. GRB 260421B: J-band upper limit with WINTER
  10. GRB 260421B: LCO optical counterpart detection
  11. GRB 260421B: Fermi GBM Observation
  12. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  13. GRB 260421A: AstroSat CZTI detection
  14. GOTO26djh/AT2026jpw: radio detection at 15GHz
  15. GRB 260412A: SVOM/ECLAIRs refined analysis
  16. GRB 260421B: SVOM/VT optical observations
  17. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  18. GRB 260310A: Late-time Chandra X-ray Detection
  19. GRB 260418A: Insight-HXMT/HE detection
  20. EP260416a: 1.3m DFOT optical observation
  21. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  22. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  23. Fermi GRB 260421C: Global MASTER-Net observations report
  24. GRB 260421C: Fermi GBM Final Real-time Localization
  25. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  26. Fermi GRB 260421B: Global MASTER-Net observations report
  27. GRB 260421B: BOOTES-7 early optical afterglow detection
  28. GRB 260421B: LCO optical afterglow confirmation
  29. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  30. GRB 260421B: TRT optical counterpart detection
  31. GRB 260421B: SVOM detection of a long burst
  32. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  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. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  46. GRB 260419B: Fermi GBM Final Real-time Localization
  47. GRB 260419A: Fermi GBM Final Real-time Localization
  48. Fermi trigger No 798275385: Global MASTER-Net observations report
  49. EP260417a: GROWTH-India Telescope optical upper limit
  50. Fermi GRB 260417B: Global MASTER-Net observations report
  51. EP260417b: GROWTH-India Telescope optical upper limit
  52. EP260416a: Ondrejov D50 optical detection
  53. GRB 260418B: Fermi GBM Final Real-time Localization
  54. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  55. EP260417a: Global MASTER-Net observations report
  56. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  57. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  58. GRB 260418A: Fermi GBM Final Real-time Localization
  59. EP260416a: GMG Optical Observation
  60. Fermi GRB 260417A: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 260411B
  62. GRB 260417B: Fermi GBM Final Real-time Localization
  63. GRB 260417A: AstroSat CZTI detection
  64. IPN triangulation of GRB 260411B
  65. EP260416a: LCO observations confirm end of flaring phase
  66. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  67. EP260417a: TRT optical counterpart detection
  68. EP260417a: Einstein Probe detection of an X-ray transient
  69. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  70. EP260417b: Einstein Probe detection of a fast X-ray transient
  71. EP-WXT trigger 01709259586: KAIT optical observations
  72. EP260416a: KAIT optical upper limit
  73. GRB 260414A: Insight-HXMT/HE detection
  74. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  75. EP260416a: WFST optical observations and rebrightening
  76. GRB 260417A: Fermi GBM Final Real-time Localization
  77. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  78. EP260416a: SVOM/VT optical observation
  79. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  80. GRB 260415B: Glowbug gamma-ray detection
  81. GRB 260411B: Glowbug gamma-ray detection
  82. GRB 260415A: Insight-HXMT/HE detection
  83. EP260416a: COLIBRÍ optical counterpart candidate
  84. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  85. EP260416a: Global MASTER-Net observations report
  86. EP260416a: Einstein Probe detection of an X-ray transient
  87. GOTO26djh/AT2026jpw : MASTER OT observation
  88. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  89. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  90. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  91. GRB 260415B: NuSTAR detection of long prompt emission
  92. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  93. GRB 260415B: Fermi GBM Final Localization
  94. GRB 260415A: Fermi GBM Final Real-time Localization
  95. Fermi trigger No 797912738: Global MASTER-Net observations report
  96. GRB 260414A: Glowbug gamma-ray detection
  97. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  98. EP260321a: CMO SAI J,K observations
  99. GRB 260412A: Insight-HXMT/HE detection
  100. GRB 260414A: Fermi GBM Final Real-time Localization

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