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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"

32541 results found.

  1. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  2. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  3. GRB 251111A: SVOM/VT optical observations with X-band data
  4. GRB 251111A: Swift-XRT observations
  5. GRB 251111A: EP-FXT counterpart detection
  6. GRB 251013C: Chandra X-ray observations and jet break detection
  7. GRB 251111A: SVOM/VT optical observations with VHF data
  8. GRB 251111A: KAIT optical upper limit
  9. GRB 251111A: LCO optical observation
  10. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  11. GRB 251103B: Swift-BAT refined analysis
  12. GRB 251106A: Swift/UVOT Upper Limits
  13. GRB 251105B: Insight-HXMT/HE detection
  14. GRB 251106B: Insight-HXMT detection
  15. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  16. GRB 251105A: AstroSat CZTI detection
  17. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  18. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  19. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  20. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  21. GRB 251102B: SVOM/GRM observation
  22. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  24. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  25. IPN triangulation of GRB 251105B (possible sGRB with EE)
  26. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  27. GRB 251106A: Swift-XRT afterglow detection
  28. GRB 251106A: Kilonova-Catcher optical upper limit
  29. Fermi GBM Sub-Threshold Detection of GRB 251106A
  30. GRB 251106A: Swift/BAT arcminute localization of a burst
  31. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  32. GRB 251106A: MASTER optical observations
  33. GRB 251103B: AstroSat CZTI detection
  34. GRB 251025C: TERI Gamma-ray detection
  35. GRB 251016B: TERI Gamma-ray detection
  36. GRB 251016A: TERI Gamma-ray detection of a short burst
  37. GRB 250920C: TERI Gamma-ray detection
  38. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  39. GRB 251105A: Fermi GBM Observation
  40. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  41. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  43. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  44. Fermi GBM Sub-Threshold Detection of GRB 251105B
  45. GRB 251103B: Swift/UVOT Upper Limits
  46. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  47. Fermi GRB 251105A: Global MASTER-Net observations report
  48. GRB 251103B: Fermi GBM observation
  49. GRB 251028A: Insight-HXMT/HE detection
  50. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  51. EP251102a: FTW optical and NIR observations
  52. GRB 251103A: WFST optical observations
  53. EP251102a: update of EP-FXT follow-up observation
  54. EP251102a: OHP/T193 optical observations
  55. GRB 251103A: OHP/T193 optical observations
  56. GRB 251103A: Xinglong 2.16m optical detection
  57. GRB 251103A: Insight-HXMT detection
  58. GRB 251103A: KAIT optical observations
  59. GRB 251103B: Nanshan/HMT optical upper limit
  60. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  61. GRB 251103B: MITSuME Akeno optical upper limits
  62. Fermi GRB 251103A: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  64. EP251102a: NIR observations with WINTER
  65. GRB 251103A: J-band detection with WINTER
  66. Swift GRB 251103B: Global MASTER-Net observations report
  67. GRB 251103B: GROWTH-India Telescope optical upper limits
  68. GRB 251103A: Kilonova-Catcher optical afterglow detection
  69. GRB 251103A: Swift/UVOT Detection
  70. GRB 251103A: Fermi GBM Observation
  71. GRB 251103A: SVOM/GRM observation
  72. GRB 251103A: Swift-XRT afterglow detection
  73. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  74. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. EP251102a: Einstein Probe detection of a fast X-ray transient
  76. GRB 251025B: OHP/T193 optical upper limit
  77. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  78. GRB 251103A: LCO optical observation
  79. GRB 251103A: GOTO optical afterglow detection
  80. GRB 251102A: AstroSat CZTI detection
  81. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  82. GRB 251103A: NOT spectroscopic redshift z = 0.76
  83. GRB 251103A: LCO optical afterglow detection
  84. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  85. GRB 251103A: NOT optical afterglow candidate
  86. Fermi GRB 251102A: Global MASTER-Net observations report
  87. GRB 251031A: Fermi GBM Observation
  88. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  89. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  90. Konus-Wind detection of GRB 251028A
  91. GRB 251025C: SVOM/GRM observation
  92. GRB 251028A: GECAM-B detection
  93. GRB 251028A: SVOM/GRM observation
  94. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  95. GRB 251028A: Fermi GBM Observation
  96. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  97. GRB 251022A: Swift-XRT confirmation of fading
  98. GRB 251026B: LBT near-infrared observations
  99. GRB 250926B: VZLUSAT-2 detection
  100. GRB 250926A: VZLUSAT-2 detection

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