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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"

41692 results found.

  1. The EP-WXT trigger 01709260362 is likely a flaring star
  2. GOTO26djh/AT2026jpw: ATCA radio detection
  3. GRB 260421B: J-band upper limit with WINTER
  4. GRB 260421B: LCO optical counterpart detection
  5. GRB 260421B: Fermi GBM Observation
  6. GRB 260421A: AstroSat CZTI detection
  7. GOTO26djh/AT2026jpw: radio detection at 15GHz
  8. GRB 260412A: SVOM/ECLAIRs refined analysis
  9. GRB 260421B: SVOM/VT optical observations
  10. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  11. GRB 260310A: Late-time Chandra X-ray Detection
  12. GRB 260418A: Insight-HXMT/HE detection
  13. EP260416a: 1.3m DFOT optical observation
  14. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  16. Fermi GRB 260421C: Global MASTER-Net observations report
  17. GRB 260421C: Fermi GBM Final Real-time Localization
  18. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  19. Fermi GRB 260421B: Global MASTER-Net observations report
  20. GRB 260421B: LCO optical afterglow confirmation
  21. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  22. GRB 260421B: TRT optical counterpart detection
  23. GRB 260421B: SVOM detection of a long burst
  24. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  25. GRB 260421B: Fermi GBM Final Real-time Localization
  26. Fermi GRB 260421A: Global MASTER-Net observations report
  27. GRB 260421A: Fermi GBM Final Real-time Localization
  28. EP260321a: VLA radio follow-up
  29. GRB 260412A: LCOGT Optical Upper Limits
  30. The EP-WXT trigger 01709260314 is likely a flaring star
  31. EP260416a: Optical follow-up observations with Kinder
  32. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  33. EP-WXT trigger 01709260303: KAIT optical observations
  34. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  35. The EP-WXT trigger 01709260303 is likely a flaring star
  36. GRB 260417A: SVOM/GRM observation
  37. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  38. GRB 260419B: Fermi GBM Final Real-time Localization
  39. GRB 260419A: Fermi GBM Final Real-time Localization
  40. Fermi trigger No 798275385: Global MASTER-Net observations report
  41. EP260417a: GROWTH-India Telescope optical upper limit
  42. Fermi GRB 260417B: Global MASTER-Net observations report
  43. EP260417b: GROWTH-India Telescope optical upper limit
  44. EP260416a: Ondrejov D50 optical detection
  45. GRB 260418B: Fermi GBM Final Real-time Localization
  46. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  47. EP260417a: Global MASTER-Net observations report
  48. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  49. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  50. GRB 260418A: Fermi GBM Final Real-time Localization
  51. Fermi GRB 260417A: Global MASTER-Net observations report
  52. Konus-Wind detection of GRB 260411B
  53. GRB 260417B: Fermi GBM Final Real-time Localization
  54. GRB 260417A: AstroSat CZTI detection
  55. EP260416a: LCO observations confirm end of flaring phase
  56. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  57. EP260417a: TRT optical counterpart detection
  58. EP260417a: Einstein Probe detection of an X-ray transient
  59. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  60. EP260417b: Einstein Probe detection of a fast X-ray transient
  61. EP-WXT trigger 01709259586: KAIT optical observations
  62. EP260416a: KAIT optical upper limit
  63. GRB 260414A: Insight-HXMT/HE detection
  64. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  65. EP260416a: WFST optical observations and rebrightening
  66. GRB 260417A: Fermi GBM Final Real-time Localization
  67. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  68. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  69. GRB 260415B: Glowbug gamma-ray detection
  70. GRB 260411B: Glowbug gamma-ray detection
  71. GRB 260415A: Insight-HXMT/HE detection
  72. EP260416a: COLIBRÍ optical counterpart candidate
  73. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  74. EP260416a: Global MASTER-Net observations report
  75. EP260416a: Einstein Probe detection of an X-ray transient
  76. GOTO26djh/AT2026jpw : MASTER OT observation
  77. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  78. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  79. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  80. GRB 260415B: NuSTAR detection of long prompt emission
  81. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  82. GRB 260415B: Fermi GBM Final Localization
  83. GRB 260415A: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 797912738: Global MASTER-Net observations report
  85. GRB 260414A: Glowbug gamma-ray detection
  86. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  87. EP260321a: CMO SAI J,K observations
  88. GRB 260412A: Insight-HXMT/HE detection
  89. GRB 260414A: Fermi GBM Final Real-time Localization
  90. The EP-WXT trigger 01709260122 is likely a flaring star
  91. Fermi GRB 260413A: Global MASTER-Net observations report
  92. GRB 260410A: Glowbug gamma-ray detection of a short burst
  93. GRB 260413A: Fermi GBM Final Real-time Localization
  94. GRB 260410B: Insight-HXMT/HE detection
  95. GRB 260410A: Insight-HXMT/HE detection
  96. Konus-Wind detection of GRB 260410A (short/hard)
  97. GRB 260411B: GECAM-B observation of a long burst
  98. EP260321a: SVOM/VT optical observations and color changes around peak
  99. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  100. The EP-WXT trigger 01709260010 is likely a flaring star

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