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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"

18280 results found.

  1. GRB 251025B: Kilonova-Catcher optical afterglow detection
  2. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  3. GRB 251026B: Tentative GOTO optical counterpart candidate
  4. GRB 251025C: AstroSat CZTI detection
  5. EP251023a: Mondy optical observations
  6. GRB 251025B: MAO/AZT-22 optical observations
  7. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  8. GRB 251025B: J-band detection with WINTER
  9. GRB 251026A: SVOM/C-GFT upper limit
  10. IceCube-251025A: DDOTI Optical Upper Limit
  11. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 251026A: SVOM detection of a long burst
  13. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  14. GRB 251023A: SVOM/GRM observation
  15. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  16. GRB 251025B: GROWTH-India Telescope optical observations
  17. GRB 251024A: Swift/UVOT Upper Limits
  18. GRB 251025B: Swift-XRT afterglow detection
  19. GRB 251025A (sb25102501): stellar flare confirmed
  20. GRB 251025B: SVOM/VT optical observations with VHF data
  21. GRB 251025B: MASTER OT detection
  22. GRB 251025B: SVOM/C-GFT optical counterpart detection
  23. GRB 251025B: SVOM detection of a burst
  24. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  25. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  26. GRB 251025A: SVOM/VT VHF optical upper limit
  27. GRB 251025A: SVOM detection of a faint burst
  28. GRB 251024A: Enhanced Swift-XRT position
  29. GRB 251024A: LCOGT Optical Afterglow Detection
  30. GRB 251022A: KAIT optical observations
  31. GRB 251024A: Swift detection of a burst
  32. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  33. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  34. EP251023a: MAO/AZT-22 optical observations
  35. GRB 251023C: AstroSat CZTI detection
  36. EP251023b/GRB 251023B: JinShan optical observation
  37. GRB 251022A: Swift-XRT detection of GOTO25iym
  38. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  39. GRB 251022A: GROWTH-India Telescope optical observations
  40. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  41. EP251023a: GROWTH-India Telescope optical observations
  42. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  43. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  44. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  45. IPN triangulation of GRB 251016B
  46. EP251023a: COLIBRÍ optical observations
  47. GRB 251013C: further SAO RAS optical observations
  48. GRB 251022A: COLIBRÍ optical observations
  49. GRB 251013C: ISON-Castelgrande observatory optical observations
  50. GRB 251022A: MASTER OT detection
  51. GRB 251022A: DDOTI Optical Detection
  52. EP251021b/GRB 251021A: SVOM/VT optical candidate
  53. EP251023a: NOT optical counterpart detection
  54. EP251023a: Einstein Probe detection of an X-ray transient
  55. GRB 251022A: Tiled Swift observations
  56. EP251021b: Einstein Probe detection of a fast X-ray transient
  57. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  58. Fermi-LAT gamma-ray observations of IceCube-251018A
  59. GRB 251017A : RAPAS follow-up observations
  60. GRB 251017A: COLIBRÍ optical observations of a late plateau
  61. IceCube-251018A: DDOTI Optical Upper Limit
  62. GRB 251018A: Enhanced Swift-XRT position
  63. IceCube-251018A: Global MASTER-Net observations report
  64. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  65. GRB 251016A: Swift-XRT afterglow detection
  66. GRB 251017A: Swift/UVOT Detection
  67. GRB 251016A: Swift/UVOT Detection
  68. GRB 251018A: Swift/UVOT Detection
  69. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  70. GRB 251016A: VLT/FORS2 Optical Observation
  71. GRB 251017A: COLIBRÍ photometric redshift
  72. GRB 251018A: MASTER OT detection
  73. GRB 251018A: TRT optical afterglow detection
  74. GRB 251018A: Swift detection of a burst with an optical counterpart
  75. GRB 251017A: J-band detection with WINTER
  76. GRB 251013C: Liverpool Telescope observations
  77. GRB 251013C: Leavitt Observatory optical photometry
  78. GRB 251017A: JinShan observations of the optical afterglow
  79. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  80. GRB 251017A: Enhanced Swift-XRT position
  81. GRB 251017A: COLIBRÍ Early Afterglow Detection
  82. GRB 251016B: AstroSat CZTI detection
  83. GRB 251017A: Swift detection of a burst with an optical counterpart
  84. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  85. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  86. sb25101602: Swift-XRT counterpart detection
  87. GRB 251016A: SVOM detection of a short burst
  88. GRB 251014A: Swift-XRT observations
  89. GRB 251014B: PRIME J-band upper limit
  90. GRB 251013C: Kilonova-Catcher optical afterglow detection
  91. GRB 251013D: Swift/UVOT Observations
  92. GRB 251013C: Swift/UVOT Detection
  93. GRB 251013C: detection of a radio counterpart at 15.5GHz
  94. Swift Trigger 1404295: possible GRB 251015A
  95. GRB 251014B: Swift/UVOT Upper Limits
  96. GRB 251014B: VLT/FORS2 Optical Observation
  97. GRB 251014D: Swift/UVOT Upper Limits
  98. GRB 251014D: Swift-XRT afterglow detection
  99. GRB 251013C: MAO/AZT-22 optical observations
  100. GRB 251011B: SVOM/VT optical upper limit

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