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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"

19089 results found.

  1. GRB 251022A: SVOM/GRM observation
  2. GRB 251026B: Swift ToO observations
  3. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  4. GRB 251027A: LCO optical upper limit
  5. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 251023B / EP251023b: Mondy optical upper limit
  7. GRB 251017A: INASAN-Kislovodsk optical observations
  8. GRB 251026A: Mondy optical upper limit
  9. GRB 251025B: Mondy optical observations
  10. GRB 251025B: Kilonova-Catcher optical afterglow detection
  11. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  12. GRB 251026B: Tentative GOTO optical counterpart candidate
  13. GRB 251025C: AstroSat CZTI detection
  14. EP251023a: Mondy optical observations
  15. GRB 251025B: MAO/AZT-22 optical observations
  16. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  17. GRB 251025B: J-band detection with WINTER
  18. GRB 251026A: SVOM/C-GFT upper limit
  19. IceCube-251025A: DDOTI Optical Upper Limit
  20. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 251026A: SVOM detection of a long burst
  22. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  23. GRB 251023A: SVOM/GRM observation
  24. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  25. GRB 251025B: GROWTH-India Telescope optical observations
  26. GRB 251024A: Swift/UVOT Upper Limits
  27. GRB 251025B: Swift-XRT afterglow detection
  28. GRB 251025A (sb25102501): stellar flare confirmed
  29. GRB 251025B: SVOM/VT optical observations with VHF data
  30. GRB 251025B: MASTER OT detection
  31. GRB 251025B: SVOM/C-GFT optical counterpart detection
  32. GRB 251025B: SVOM detection of a burst
  33. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  34. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 251025A: SVOM/VT VHF optical upper limit
  36. GRB 251025A: SVOM detection of a faint burst
  37. GRB 251024A: Enhanced Swift-XRT position
  38. GRB 251024A: LCOGT Optical Afterglow Detection
  39. GRB 251022A: KAIT optical observations
  40. GRB 251024A: Swift detection of a burst
  41. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  42. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  43. EP251023a: MAO/AZT-22 optical observations
  44. GRB 251023C: AstroSat CZTI detection
  45. EP251023b/GRB 251023B: JinShan optical observation
  46. GRB 251022A: Swift-XRT detection of GOTO25iym
  47. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  48. GRB 251022A: GROWTH-India Telescope optical observations
  49. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  50. EP251023a: GROWTH-India Telescope optical observations
  51. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  52. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  53. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  54. IPN triangulation of GRB 251016B
  55. EP251023a: COLIBRÍ optical observations
  56. GRB 251013C: further SAO RAS optical observations
  57. GRB 251022A: COLIBRÍ optical observations
  58. GRB 251013C: ISON-Castelgrande observatory optical observations
  59. GRB 251022A: MASTER OT detection
  60. GRB 251022A: DDOTI Optical Detection
  61. EP251021b/GRB 251021A: SVOM/VT optical candidate
  62. EP251023a: NOT optical counterpart detection
  63. EP251023a: Einstein Probe detection of an X-ray transient
  64. GRB 251022A: Tiled Swift observations
  65. EP251021b: Einstein Probe detection of a fast X-ray transient
  66. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  67. Fermi-LAT gamma-ray observations of IceCube-251018A
  68. GRB 251017A : RAPAS follow-up observations
  69. GRB 251017A: COLIBRÍ optical observations of a late plateau
  70. IceCube-251018A: DDOTI Optical Upper Limit
  71. GRB 251018A: Enhanced Swift-XRT position
  72. IceCube-251018A: Global MASTER-Net observations report
  73. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  74. GRB 251016A: Swift-XRT afterglow detection
  75. GRB 251017A: Swift/UVOT Detection
  76. GRB 251016A: Swift/UVOT Detection
  77. GRB 251018A: Swift/UVOT Detection
  78. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  79. GRB 251016A: VLT/FORS2 Optical Observation
  80. GRB 251017A: COLIBRÍ photometric redshift
  81. GRB 251018A: MASTER OT detection
  82. GRB 251018A: TRT optical afterglow detection
  83. GRB 251018A: Swift detection of a burst with an optical counterpart
  84. GRB 251017A: J-band detection with WINTER
  85. GRB 251013C: Liverpool Telescope observations
  86. GRB 251013C: Leavitt Observatory optical photometry
  87. GRB 251017A: JinShan observations of the optical afterglow
  88. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  89. GRB 251017A: Enhanced Swift-XRT position
  90. GRB 251017A: COLIBRÍ Early Afterglow Detection
  91. GRB 251016B: AstroSat CZTI detection
  92. GRB 251017A: Swift detection of a burst with an optical counterpart
  93. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  94. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  95. sb25101602: Swift-XRT counterpart detection
  96. GRB 251016A: SVOM detection of a short burst
  97. GRB 251014A: Swift-XRT observations
  98. GRB 251014B: PRIME J-band upper limit
  99. GRB 251013C: Kilonova-Catcher optical afterglow detection
  100. GRB 251013D: Swift/UVOT Observations

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