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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"

18048 results found.

  1. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  2. EP251023a: MAO/AZT-22 optical observations
  3. GRB 251023C: AstroSat CZTI detection
  4. EP251023b/GRB 251023B: JinShan optical observation
  5. GRB 251022A: Swift-XRT detection of GOTO25iym
  6. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  7. GRB 251022A: GROWTH-India Telescope optical observations
  8. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  9. EP251023a: GROWTH-India Telescope optical observations
  10. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  11. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  12. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  13. IPN triangulation of GRB 251016B
  14. EP251023a: COLIBRÍ optical observations
  15. GRB 251013C: further SAO RAS optical observations
  16. GRB 251022A: COLIBRÍ optical observations
  17. GRB 251013C: ISON-Castelgrande observatory optical observations
  18. GRB 251022A: MASTER OT detection
  19. GRB 251022A: DDOTI Optical Detection
  20. EP251021b/GRB 251021A: SVOM/VT optical candidate
  21. EP251023a: NOT optical counterpart detection
  22. EP251023a: Einstein Probe detection of an X-ray transient
  23. GRB 251022A: Tiled Swift observations
  24. EP251021b: Einstein Probe detection of a fast X-ray transient
  25. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  26. Fermi-LAT gamma-ray observations of IceCube-251018A
  27. GRB 251017A : RAPAS follow-up observations
  28. GRB 251017A: COLIBRÍ optical observations of a late plateau
  29. IceCube-251018A: DDOTI Optical Upper Limit
  30. GRB 251018A: Enhanced Swift-XRT position
  31. IceCube-251018A: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  33. GRB 251016A: Swift-XRT afterglow detection
  34. GRB 251017A: Swift/UVOT Detection
  35. GRB 251016A: Swift/UVOT Detection
  36. GRB 251018A: Swift/UVOT Detection
  37. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  38. GRB 251016A: VLT/FORS2 Optical Observation
  39. GRB 251017A: COLIBRÍ photometric redshift
  40. GRB 251018A: MASTER OT detection
  41. GRB 251018A: TRT optical afterglow detection
  42. GRB 251018A: Swift detection of a burst with an optical counterpart
  43. GRB 251017A: J-band detection with WINTER
  44. GRB 251013C: Liverpool Telescope observations
  45. GRB 251013C: Leavitt Observatory optical photometry
  46. GRB 251017A: JinShan observations of the optical afterglow
  47. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  48. GRB 251017A: Enhanced Swift-XRT position
  49. GRB 251017A: COLIBRÍ Early Afterglow Detection
  50. GRB 251016B: AstroSat CZTI detection
  51. GRB 251017A: Swift detection of a burst with an optical counterpart
  52. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  53. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  54. sb25101602: Swift-XRT counterpart detection
  55. GRB 251016A: SVOM detection of a short burst
  56. GRB 251014A: Swift-XRT observations
  57. GRB 251014B: PRIME J-band upper limit
  58. GRB 251013C: Kilonova-Catcher optical afterglow detection
  59. GRB 251013D: Swift/UVOT Observations
  60. GRB 251013C: Swift/UVOT Detection
  61. GRB 251013C: detection of a radio counterpart at 15.5GHz
  62. Swift Trigger 1404295: possible GRB 251015A
  63. GRB 251014B: Swift/UVOT Upper Limits
  64. GRB 251014B: VLT/FORS2 Optical Observation
  65. GRB 251014D: Swift/UVOT Upper Limits
  66. GRB 251014D: Swift-XRT afterglow detection
  67. GRB 251013C: MAO/AZT-22 optical observations
  68. GRB 251011B: SVOM/VT optical upper limit
  69. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  70. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  71. GRB 251014D: Swift detection of a burst
  72. GRB 251014A: PRIME near-infrared upper limits
  73. GRB 251014A: VLT/FORS2 Optical Observation
  74. GRB 251013C: MarSEC, optical afterglow photometry
  75. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  76. GRB 251014B: Swift ToO observations
  77. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  78. GRB 251013C: Bassano Bresciano Observatory optical observations
  79. GRB 251013C: Early and late-time optical counterpart detection by LCO
  80. GRB 251013D: Swift ToO observations
  81. GRB 251014A: DDOTI Upper Limit
  82. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  83. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  84. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  85. GRB 251013C: Asiago optical observations
  86. GRB 251013C: ABObservatory optical observations
  87. GRB 251014A: SAO RAS optical upper limit
  88. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  89. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  90. GRB 251013C: DDOTI detection of the optical afterglow
  91. GRB 251013C: SAO RAS optical observations
  92. GRB 251013C: LCO optical afterglow detection
  93. GRB 251013C: LAST detection of optical counterpart
  94. GRB 251013C: SVOM/VT optical observation
  95. GRB 251013C: SVOM detection of a burst
  96. GRB 251013B: SVOM/GRM observation
  97. GRB 251013A: SVOM/GRM observation
  98. GRB 251003A: Mondy optical upper limit
  99. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  100. GRB 251011B inspection: MASTER orphan GRB detection

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