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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"

15564 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. EP251023a: Mondy optical observations
  5. GRB 251025B: MAO/AZT-22 optical observations
  6. GRB 251025B: OHP/T193 optical detection
  7. GRB 251025B: J-band detection with WINTER
  8. IceCube-251025A: DDOTI Optical Upper Limit
  9. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. GRB 251025B: SVOM/VT optical bump
  11. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  12. GRB 251023A: SVOM/GRM observation
  13. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  14. GRB 251025B: GROWTH-India Telescope optical observations
  15. GRB 251024A: Swift/UVOT Upper Limits
  16. GRB 251025B: SVOM/VT optical observations with VHF data
  17. GRB 251025B: MASTER OT detection
  18. GRB 251025B: SVOM/C-GFT optical counterpart detection
  19. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  20. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 251025A: SVOM/VT VHF optical upper limit
  22. GRB 251024A: LCOGT Optical Afterglow Detection
  23. GRB 251022A: KAIT optical observations
  24. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  25. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  26. EP251023a: MAO/AZT-22 optical observations
  27. GRB 251023B: OHP/T193 optical observations
  28. EP251023a: OHP/T193 optical observations
  29. EP251023b/GRB 251023B: JinShan optical observation
  30. GRB 251022A: Swift-XRT detection of GOTO25iym
  31. GRB 251022A: GROWTH-India Telescope optical observations
  32. EP251023a: GROWTH-India Telescope optical observations
  33. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  34. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  35. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  36. EP251023a: COLIBRÍ optical observations
  37. GRB 251013C: further SAO RAS optical observations
  38. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  39. GRB 251022A: COLIBRÍ optical observations
  40. GRB 251013C: ISON-Castelgrande observatory optical observations
  41. GRB 251022A: MASTER OT detection
  42. GRB 251022A: DDOTI Optical Detection
  43. EP251021b/GRB 251021A: SVOM/VT optical candidate
  44. EP251023a: NOT optical counterpart detection
  45. EP251023a: GSP Optical Counterpart Detection
  46. EP251023a: Einstein Probe detection of an X-ray transient
  47. EP/WXT 01709247295: GOTO optical afterglow candidate.
  48. GRB 251022A: GOTO optical counterpart detection
  49. EP251021b: BOOTES-7 optical upper limit
  50. GRB 251017A: COLIBRÍ optical observations of a late plateau
  51. IceCube-251018A: DDOTI Optical Upper Limit
  52. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  53. GRB 251016A: Swift/UVOT Detection
  54. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  55. GRB 251016A: VLT/FORS2 Optical Observation
  56. GRB 251018A: MASTER OT detection
  57. GRB 251018A: TRT optical afterglow detection
  58. GRB 251018A: Swift detection of a burst with an optical counterpart
  59. GRB 251017A: SVOM/VT optical observation
  60. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  61. GRB 251017A: J-band detection with WINTER
  62. GRB 251013C: Liverpool Telescope observations
  63. GRB 251013C: Leavitt Observatory optical photometry
  64. GRB 251017A: JinShan observations of the optical afterglow
  65. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  66. GRB 251017A: COLIBRÍ Early Afterglow Detection
  67. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  68. GRB 251017A: Swift detection of a burst with an optical counterpart
  69. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  70. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  71. GRB 251016A: BOOTES-6/DPRT optical upper limit
  72. GRB 251013C: VLA detection
  73. GRB 251016A: SVOM detection of a short burst
  74. GRB 251014B: PRIME J-band upper limit
  75. GRB 251013C: Kilonova-Catcher optical afterglow detection
  76. GRB 251013D: Swift/UVOT Observations
  77. GRB 251013C: Swift/UVOT Detection
  78. GRB 251014B: Swift/UVOT Upper Limits
  79. GRB 251014B: VLT/FORS2 Optical Observation
  80. GRB 251014D: Swift/UVOT Upper Limits
  81. GRB 251014D: BOOTES-6/DPRT optical upper limit
  82. GRB 251013C: MAO/AZT-22 optical observations
  83. GRB 251011B: SVOM/VT optical upper limit
  84. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  85. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  86. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  87. GRB 251014A: VLT/FORS2 Optical Observation
  88. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  89. GRB 251013C: MarSEC, optical afterglow photometry
  90. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  91. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  92. GRB 251013C: Bassano Bresciano Observatory optical observations
  93. GRB 251013C: Early and late-time optical counterpart detection by LCO
  94. GRB 251014A: DDOTI Upper Limit
  95. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  96. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  97. GRB 251013C: Asiago optical observations
  98. GRB 251013C: ABObservatory optical observations
  99. GRB 251014A: SAO RAS optical upper limit
  100. GRB 251013C: J band observations by SYSU 80cm infrared telescope

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