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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"

32531 results found.

  1. GRB 251103B: Swift-BAT refined analysis
  2. GRB 251106A: Swift/UVOT Upper Limits
  3. GRB 251105B: Insight-HXMT/HE detection
  4. GRB 251106B: Insight-HXMT detection
  5. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  6. GRB 251105A: AstroSat CZTI detection
  7. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  8. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  9. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  10. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  11. GRB 251102B: SVOM/GRM observation
  12. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  13. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  14. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  15. IPN triangulation of GRB 251105B (possible sGRB with EE)
  16. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  17. GRB 251106A: Swift-XRT afterglow detection
  18. GRB 251106A: Kilonova-Catcher optical upper limit
  19. Fermi GBM Sub-Threshold Detection of GRB 251106A
  20. GRB 251106A: Swift/BAT arcminute localization of a burst
  21. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  22. GRB 251106A: MASTER optical observations
  23. GRB 251103B: AstroSat CZTI detection
  24. GRB 251025C: TERI Gamma-ray detection
  25. GRB 251016B: TERI Gamma-ray detection
  26. GRB 251016A: TERI Gamma-ray detection of a short burst
  27. GRB 250920C: TERI Gamma-ray detection
  28. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  29. GRB 251105A: Fermi GBM Observation
  30. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  31. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  33. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  34. Fermi GBM Sub-Threshold Detection of GRB 251105B
  35. GRB 251103B: Swift/UVOT Upper Limits
  36. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  37. Fermi GRB 251105A: Global MASTER-Net observations report
  38. GRB 251103B: Fermi GBM observation
  39. GRB 251028A: Insight-HXMT/HE detection
  40. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  41. EP251102a: FTW optical and NIR observations
  42. GRB 251103A: WFST optical observations
  43. EP251102a: update of EP-FXT follow-up observation
  44. EP251102a: OHP/T193 optical observations
  45. GRB 251103A: OHP/T193 optical observations
  46. GRB 251103A: Xinglong 2.16m optical detection
  47. GRB 251103A: Insight-HXMT detection
  48. GRB 251103A: KAIT optical observations
  49. GRB 251103B: Nanshan/HMT optical upper limit
  50. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  51. GRB 251103B: MITSuME Akeno optical upper limits
  52. Fermi GRB 251103A: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  54. EP251102a: NIR observations with WINTER
  55. GRB 251103A: J-band detection with WINTER
  56. Swift GRB 251103B: Global MASTER-Net observations report
  57. GRB 251103B: GROWTH-India Telescope optical upper limits
  58. GRB 251103A: Kilonova-Catcher optical afterglow detection
  59. GRB 251103A: Swift/UVOT Detection
  60. GRB 251103A: Fermi GBM Observation
  61. GRB 251103A: SVOM/GRM observation
  62. GRB 251103A: Swift-XRT afterglow detection
  63. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  64. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. EP251102a: Einstein Probe detection of a fast X-ray transient
  66. GRB 251025B: OHP/T193 optical upper limit
  67. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  68. GRB 251103A: LCO optical observation
  69. GRB 251103A: GOTO optical afterglow detection
  70. GRB 251102A: AstroSat CZTI detection
  71. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  72. GRB 251103A: NOT spectroscopic redshift z = 0.76
  73. GRB 251103A: LCO optical afterglow detection
  74. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  75. GRB 251103A: NOT optical afterglow candidate
  76. Fermi GRB 251102A: Global MASTER-Net observations report
  77. GRB 251031A: Fermi GBM Observation
  78. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  79. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  80. Konus-Wind detection of GRB 251028A
  81. GRB 251025C: SVOM/GRM observation
  82. GRB 251028A: GECAM-B detection
  83. GRB 251028A: SVOM/GRM observation
  84. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  85. GRB 251028A: Fermi GBM Observation
  86. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  87. GRB 251022A: Swift-XRT confirmation of fading
  88. GRB 251026B: LBT near-infrared observations
  89. GRB 250926B: VZLUSAT-2 detection
  90. GRB 250926A: VZLUSAT-2 detection
  91. GRB 250925A: VZLUSAT-2 detection
  92. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  93. GRB 251026A/EP251026a: EP-FXT follow-up observation
  94. GRB 251028B: Fermi/GBM observation
  95. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  96. GRB 251028B: Glowbug gamma-ray detection
  97. GRB 251028A: Glowbug gamma-ray detection
  98. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  99. Fermi GRB 251028B: Global MASTER-Net observations report
  100. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening

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