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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"

15985 results found.

  1. GRB 251014D: Swift/UVOT Upper Limits
  2. GRB 251014D: BOOTES-6/DPRT optical upper limit
  3. GRB 251013C: MAO/AZT-22 optical observations
  4. GRB 251011B: SVOM/VT optical upper limit
  5. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  6. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  7. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  8. GRB 251014A: VLT/FORS2 Optical Observation
  9. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  10. GRB 251013C: MarSEC, optical afterglow photometry
  11. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  12. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  13. GRB 251013C: Bassano Bresciano Observatory optical observations
  14. GRB 251013C: Early and late-time optical counterpart detection by LCO
  15. GRB 251014A: DDOTI Upper Limit
  16. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  17. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  18. GRB 251013C: Asiago optical observations
  19. GRB 251013C: ABObservatory optical observations
  20. GRB 251014A: SAO RAS optical upper limit
  21. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  22. GRB 251013C: EP-FXT counterpart detection
  23. GRB 251013C: ALMA detection
  24. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  25. GRB 251013C: DDOTI detection of the optical afterglow
  26. GRB 251013C: SLKT optical afterglow photometry
  27. GRB 251013C: Swift-XRT counterpart detection
  28. GRB 251013C: GOTO optical afterglow detection
  29. GRB 251013C: SAO RAS optical observations
  30. GRB 251013C: LCO optical afterglow detection
  31. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  32. GRB 251013C: NOT spectroscopic redshift z = 0.572
  33. GRB 251013C: LAST detection of optical counterpart
  34. GRB 251013C: BOOTES-6 early optical detection
  35. GRB 251013C: SVOM/VT optical observation
  36. GRB 251013B: SVOM/GRM observation
  37. GRB 251013A: SVOM/GRM observation
  38. GRB 251003A: Mondy optical upper limit
  39. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  40. GRB 251011B inspection: MASTER orphan GRB detection
  41. GRB 251011B: Swift/UVOT Upper Limits
  42. GRB 251011B: SVOM/GRM observation
  43. GRB 251011B : MASTER optical observations
  44. GRB 251007B: Swift/UVOT Upper Limits
  45. GRB251007A: Swift/UVOT Detection
  46. GRB 251007A: SVOM/GRM observation
  47. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  48. GRB 251007B: COLIBRÍ optical upper limit
  49. GRB 251006B/EP251006a: EP-FXT afterglow detection
  50. GRB 250917B: iTelescope T-26 upper limit
  51. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  52. GRB 251007B: SVOM/VT optical candidate
  53. GRB 251007A: NOT optical observations
  54. GRB 251007A: AKO Optical Upper Limit
  55. GRB 251007A: SVOM/C-GFT optical observations
  56. GRB 251007B: SVOM detection of a faint burst
  57. GRB 251007A: Swift detection of a burst with an optical counterpart
  58. EP251003a: LCO and VST fading optical counterpart
  59. GRB 251006B/EP251006a: SVOM/VT optical candidate
  60. GRB 251006B/EP251006a: EP-FXT follow-up observation
  61. GRB 251006B: SVOM/GRM observation
  62. GRB 251006B: COLIBRÍ optical upper limit
  63. GRB 251005C: SVOM/VT optical fading
  64. GRB 251005C: SVOM/GRM observation of a likely short GRB
  65. GRB 251005C: COLIBRÍ optical observations
  66. GRB 251005C: VLT/X-shooter Imaging
  67. GRB 251003A: LAST optical observations
  68. GRB 251002A: LAST optical observations
  69. GRB 251005C: SVOM/VT optical candidate
  70. GRB 251005C: Swift/UVOT Upper Limits
  71. GRB 251005C: GOTO optical upper limits
  72. GRB 251002A: Mondy/AZT-33IK optical observations
  73. GRB 251003A: J-band detection with WINTER
  74. GRB 251002A: NIR observations with WINTER
  75. Fermi GBM Sub-Threshold Detection of GRB 250910A
  76. GRB 251001B: NIR observations with WINTER
  77. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  78. GRB 251003A: Swift/UVOT Upper Limits
  79. GRB 251002A: Swift/UVOT detection
  80. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  81. GRB 251003A: GOTO detection of the optical counterpart
  82. GRB 251002A: GOTO detection of optical counterpart
  83. GRB 251001C: SVOM/GRM observation
  84. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  85. GRB 251002A: AKO Early Optical Afterglow Detection
  86. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  87. GRB 251003A: Kilonova-Catcher optical afterglow detection
  88. GRB 251002A: Swift-XRT afterglow detection
  89. GRB 251001B: AbAO optical upper limit
  90. GRB 251002A: Kilonova-Catcher optical afterglow detection
  91. GRB 251002A: AbAO optical observations
  92. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  93. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  94. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  95. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  96. GRB 251002A: EP-FXT counterpart detection
  97. GRB 251003A: LCOGT Optical Detection
  98. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  99. GRB 251003A: 1.5m OSN afterglow candidate
  100. Swift GRB251003A: Global MASTER-Net observations report

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