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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 S251018bi: Identification of a GW compact binary merger candidate
  2. GRB 251016A: Swift-XRT afterglow detection
  3. GRB 251017A: Swift/UVOT Detection
  4. GRB 251016A: Swift/UVOT Detection
  5. GRB 251018A: Swift/UVOT Detection
  6. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  7. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  8. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  9. GRB 251016A: VLT/FORS2 Optical Observation
  10. GRB 251017A: COLIBRÍ photometric redshift
  11. GRB 251017A: Swift-XRT refined Analysis
  12. GRB 251018A: MASTER OT detection
  13. GRB 251018A: TRT optical afterglow detection
  14. Swift GRB 251018A: Global MASTER-Net observations report
  15. GRB 251018A: Swift detection of a burst with an optical counterpart
  16. GRB 251018A: Fermi GBM Final Real-time Localization
  17. GRB 251017A: SVOM/VT optical observation
  18. GRB 251011A: Fermi GBM Observation
  19. GRB 251017A: OHP/T193 i-band observations
  20. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  21. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  22. GRB 251017A: J-band detection with WINTER
  23. GRB 251017A: Glowbug gamma-ray detection
  24. GRB 251013C: Liverpool Telescope observations
  25. GRB 251013C: Leavitt Observatory optical photometry
  26. Fermi GRB 251016B: Global MASTER-Net observations report
  27. GRB 251017A: JinShan observations of the optical afterglow
  28. Swift GRB 251017A: Global MASTER-Net observations report
  29. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  30. Swift Trigger 1404295 is not a GRB
  31. GRB 251016A: AstroSat CZTI detection of a short burst
  32. GRB 251017A: Enhanced Swift-XRT position
  33. GRB 251017A: COLIBRÍ Early Afterglow Detection
  34. GRB 251016B: AstroSat CZTI detection
  35. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  36. GRB 251017A: Swift detection of a burst with an optical counterpart
  37. GRB 251016A: CALET Gamma-Ray Burst Monitor detection
  38. GRB 251016B: CALET Gamma-Ray Burst Monitor detection
  39. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  40. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  41. GRB 251007B: Swift-BAT refined analysis
  42. GRB 251016B: Fermi GBM Final Real-time Localization
  43. GRB 251014D: Swift-BAT refined analysis
  44. GRB 251016A: BOOTES-6/DPRT optical upper limit
  45. GRB 251016A: Glowbug gamma-ray detection of a short burst
  46. GRB 251013C: VLA detection
  47. sb25101602: Swift-XRT counterpart detection
  48. Fermi GRB 251016A: Global MASTER-Net observations report
  49. GRB 251016A: Fermi GBM Final Localization
  50. GRB 251016A: SVOM detection of a short burst
  51. GRB 251014A: Swift-XRT observations
  52. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  53. GRB 251014B: PRIME J-band upper limit
  54. Upper limits from a search for additional neutrino events in IceCube
  55. IceCube Alert 251014.77: Global MASTER-Net observations report
  56. Swift GRB251015.60: Global MASTER-Net observations report
  57. GRB 251013C: Kilonova-Catcher optical afterglow detection
  58. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  59. GRB 251013D: Swift/UVOT Observations
  60. GRB 251013C: Swift/UVOT Detection
  61. Konus-Wind detection of GRB 251007A
  62. Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB
  63. GRB 251013C, GCN Circular 42267, errata corrige
  64. GRB 251013C: detection of a radio counterpart at 15.5GHz
  65. GRB 251015A: Fermi GBM Final Real-time Localization
  66. GRB 251013C: SVOM/ECLAIRs refined analysis
  67. GRB 251013D: Swift-XRT observations
  68. Swift Trigger 1404295: possible GRB 251015A
  69. GRB 251014B: Swift-XRT observations
  70. GRB 251014B: Swift/UVOT Upper Limits
  71. GRB 251014B: VLT/FORS2 Optical Observation
  72. GRB 251014D: Swift/UVOT Upper Limits
  73. GRB 251014D: BOOTES-6/DPRT optical upper limit
  74. GRB 251014D: Swift-XRT afterglow detection
  75. GRB 251013C: MAO/AZT-22 optical observations
  76. GRB 251011B: SVOM/VT optical upper limit
  77. GRB 251013C: Swift ToO observations
  78. GRB 251013D: Fermi GBM Observation
  79. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  80. GRB 251014A: Swift-BAT refined analysis
  81. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  83. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  84. GRB 251014D: Swift detection of a burst
  85. GRB 251014A: PRIME near-infrared upper limits
  86. GRB 251014C: Fermi GBM Final Localization
  87. GRB 251014A: Glowbug gamma-ray detection of a likely short burst
  88. GRB 251014A: VLT/FORS2 Optical Observation
  89. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  90. GRB 251012A: Glowbug gamma-ray detection of a likely short burst
  91. GRB 251013C: MarSEC, optical afterglow photometry
  92. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  93. GRB 251014B: Swift ToO observations
  94. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  95. GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
  96. GRB 251013C: Bassano Bresciano Observatory optical observations
  97. GRB 251013C: Early and late-time optical counterpart detection by LCO
  98. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  99. GRB 251013C: Fermi GBM Observation
  100. GRB 251013D: Swift ToO observations

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