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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"

20212 results found.

  1. GRB 251016A: Swift-XRT afterglow detection
  2. GRB 251017A: Swift/UVOT Detection
  3. GRB 251016A: Swift/UVOT Detection
  4. GRB 251018A: Swift/UVOT Detection
  5. GRB 251016A: VLT/FORS2 Optical Observation
  6. GRB 251017A: COLIBRÍ photometric redshift
  7. GRB 251018A: MASTER OT detection
  8. GRB 251018A: TRT optical afterglow detection
  9. GRB 251018A: Swift detection of a burst with an optical counterpart
  10. GRB 251017A: J-band detection with WINTER
  11. GRB 251013C: Liverpool Telescope observations
  12. GRB 251013C: Leavitt Observatory optical photometry
  13. GRB 251017A: JinShan observations of the optical afterglow
  14. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  15. GRB 251017A: Enhanced Swift-XRT position
  16. GRB 251017A: COLIBRÍ Early Afterglow Detection
  17. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  18. GRB 251017A: Swift detection of a burst with an optical counterpart
  19. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  20. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  21. sb25101602: Swift-XRT counterpart detection
  22. GRB 251016A: SVOM detection of a short burst
  23. GRB 251014A: Swift-XRT observations
  24. GRB 251014B: PRIME J-band upper limit
  25. GRB 251013C: Kilonova-Catcher optical afterglow detection
  26. GRB 251013D: Swift/UVOT Observations
  27. GRB 251013C: Swift/UVOT Detection
  28. Konus-Wind detection of GRB 251007A
  29. GRB 251013C: detection of a radio counterpart at 15.5GHz
  30. Swift Trigger 1404295: possible GRB 251015A
  31. GRB 251014B: Swift/UVOT Upper Limits
  32. GRB 251014B: VLT/FORS2 Optical Observation
  33. GRB 251014D: Swift/UVOT Upper Limits
  34. GRB 251014D: Swift-XRT afterglow detection
  35. GRB 251013C: MAO/AZT-22 optical observations
  36. GRB 251011B: SVOM/VT optical upper limit
  37. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  38. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  39. GRB 251014D: Swift detection of a burst
  40. GRB 251014A: PRIME near-infrared upper limits
  41. GRB 251014A: VLT/FORS2 Optical Observation
  42. GRB 251013C: MarSEC, optical afterglow photometry
  43. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  44. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  45. GRB 251013C: Bassano Bresciano Observatory optical observations
  46. GRB 251013C: Early and late-time optical counterpart detection by LCO
  47. GRB 251013C: Fermi GBM Observation
  48. GRB 251014A: DDOTI Upper Limit
  49. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  50. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  51. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  52. GRB 251013C: Asiago optical observations
  53. GRB 251013C: ABObservatory optical observations
  54. GRB 251014A: SAO RAS optical upper limit
  55. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  56. GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
  57. GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
  58. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  59. GRB 251013C: DDOTI detection of the optical afterglow
  60. GRB 251013C: SAO RAS optical observations
  61. GRB 251013C: LCO optical afterglow detection
  62. GRB 251013C: LAST detection of optical counterpart
  63. GRB 251013C: SVOM/VT optical observation
  64. GRB 251013C: SVOM detection of a burst
  65. GRB 251013B: SVOM/GRM observation
  66. GRB 251013A: SVOM/GRM observation
  67. GRB 251003A: Mondy optical upper limit
  68. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  69. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  70. GRB 251011B inspection: MASTER orphan GRB detection
  71. GRB 251011B: Swift/UVOT Upper Limits
  72. GRB 251011B: SVOM/GRM observation
  73. GRB 251011B: Fermi GBM Observation
  74. GRB 251011B : MASTER optical observations
  75. GRB 251011B: Enhanced Swift-XRT position
  76. GRB 251011B: Swift detection of a burst
  77. GRB 251007B: Swift/UVOT Upper Limits
  78. GRB251007A: Swift/UVOT Detection
  79. GRB 251007A: Swift-BAT refined analysis
  80. GRB 251007A: SVOM/GRM observation
  81. GRB 251007B - SVOM/ECLAIRs refined analysis
  82. SVOM/sb25101004: SVOM detection of a stellar flare
  83. GRB 251002A - SVOM/ECLAIRs refined analysis
  84. GRB 251007B: COLIBRÍ optical upper limit
  85. GRB 250917B: iTelescope T-26 upper limit
  86. GRB 251007A: Enhanced Swift-XRT position
  87. GRB 251007B: Swift-XRT refined Analysis
  88. GRB 251007B: Enhanced Swift-XRT position
  89. GRB 251007A: AKO Optical Upper Limit
  90. GRB 251007A: SVOM/C-GFT optical observations
  91. GRB 251005C: PRIME J-band upper limit
  92. Swift GRB 251007B: Global MASTER-Net observations report
  93. GRB 251007B: SVOM/C-GFT upper limit
  94. GRB 251007B: Swift detection of a burst
  95. GRB 251007A: Swift detection of a burst with an optical counterpart
  96. GRB 250702B/EP250702a: JWST/NIRCam Observations
  97. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  98. GRB 251006B: SVOM/GRM observation
  99. GRB 251006B: COLIBRÍ optical upper limit
  100. GRB 251006B/EP251006a: EP-WXT detection

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