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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"
  1. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  2. SVOM GRB251106.83: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  4. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  5. IPN triangulation of GRB 251105B (possible sGRB with EE)
  6. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  7. GRB 251106B: SVOM/GRM observation of a short burst
  8. GRB 251106A: Swift-XRT afterglow detection
  9. GRB 251106A: Swift/BAT arcminute localization of a burst
  10. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  11. GRB 251106A: MASTER optical observations
  12. GRB 251106A: SVOM detection of a burst
  13. GRB 251103B: AstroSat CZTI detection
  14. GRB 251025C: TERI Gamma-ray detection
  15. GRB 251016B: TERI Gamma-ray detection
  16. GRB 251016A: TERI Gamma-ray detection of a short burst
  17. GRB 250920C: TERI Gamma-ray detection
  18. Fermi trigger No 784034269: Global MASTER-Net observations report
  19. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  20. GRB 251105A: Fermi GBM Observation
  21. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  22. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  23. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  24. Fermi GBM Sub-Threshold Detection of GRB 251105B
  25. GRB 251103B: Swift/UVOT Upper Limits
  26. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  27. Fermi GRB 251105A: Global MASTER-Net observations report
  28. GRB 251105A: Fermi GBM Final Real-time Localization
  29. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  30. GRB 251103B: Fermi GBM observation
  31. GRB 251104A: SVOM detection of a burst
  32. GRB 251028A: Insight-HXMT/HE detection
  33. GRB 251103A: WFST optical observations
  34. EP251102a: update of EP-FXT follow-up observation
  35. GRB 251103A: Xinglong 2.16m optical detection
  36. GRB 251103A: Insight-HXMT detection
  37. GRB 251103A: KAIT optical observations
  38. GRB 251103B: Nanshan/HMT optical upper limit
  39. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  40. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  41. Fermi GRB 251103A: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  43. GRB 251103B: GROWTH-India Telescope optical upper limits
  44. GRB 251103B: Swift detection of a burst
  45. GRB 251103A: SVOM/GRM observation
  46. GRB 251103A: Swift-XRT afterglow detection
  47. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  48. GRB 251025B: OHP/T193 optical upper limit
  49. GRB 251103A: LCO optical observation
  50. EP251102.890: COLIBRÍ optical counterpart candidate
  51. GRB 251103A: GOTO optical afterglow detection
  52. GRB 251102A: AstroSat CZTI detection
  53. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  54. GRB 251103A: NOT spectroscopic redshift z = 0.76
  55. GRB 251103A: BOOTES-2/TELMA optical afterglow
  56. GRB 251103A: LCO optical afterglow detection
  57. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  58. GRB 251103A: Fermi GBM Final Localization
  59. GRB 251103A: SVOM detection of a bright burst
  60. GRB 251102B: Fermi GBM Final Real-time Localization
  61. Fermi GRB 251102A: Global MASTER-Net observations report
  62. GRB 251102A: Fermi GBM Final Real-time Localization
  63. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  64. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  65. Konus-Wind detection of GRB 251028A
  66. GRB 251031A: Fermi GBM Final Real-time Localization
  67. GRB 251028A: SVOM/GRM observation
  68. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  69. GRB 251028A: Fermi GBM Observation
  70. GRB 251026B: LBT near-infrared observations
  71. GRB 250926B: VZLUSAT-2 detection
  72. GRB 250926A: VZLUSAT-2 detection
  73. GRB 250925A: VZLUSAT-2 detection
  74. GRB 251026B: Fermi GBM Observation
  75. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  76. GRB 251026A/EP251026a: EP-FXT follow-up observation
  77. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  78. GRB 251028A: Glowbug gamma-ray detection
  79. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  80. Fermi GRB 251028B: Global MASTER-Net observations report
  81. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  82. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  83. GRB 251028A: MAXI/GSC detection
  84. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  85. GRB 251025B: Swift-XRT confirmation of fading
  86. GRB 251023B: Swift-UVOT Upper Limits
  87. Konus-Wind detection of GRB 251022A
  88. GRB 251027A: Swift-XRT observations
  89. EP251027.145: COLIBRÍ optical upper limits
  90. GRB 251026B: Swift ToO observations
  91. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  92. GRB 251027A: LCO optical upper limit
  93. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  95. GRB 251023B / EP251023b: Mondy optical upper limit
  96. GRB 251017A: INASAN-Kislovodsk optical observations
  97. GRB 251026A: Mondy optical upper limit
  98. GRB 251025B: Mondy optical observations
  99. Konus-Wind detection of GRB 251016A (short/hard)
  100. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003

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