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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"

19857 results found.

  1. GRB 250331B: Enhanced Swift-XRT position
  2. GRB 250320C : SVOM detection of a burst through offline search
  3. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  4. GRB 250330A: VLT/FORS2 Afterglow Detection
  5. GRB20250327B: 45th Parallel Observatory upper limit
  6. GRB 250328A: Swift/UVOT Detection
  7. GRB 250328A: Swift-XRT refined Analysis
  8. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  9. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  10. GRB 250331C: Swift detection of a burst
  11. GRB 250331B: Swift detection of a burst
  12. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  13. GRB 250330A: Swift/UVOT Upper Limits
  14. GRB 250330A: Swift-XRT afterglow detection
  15. GRB 250328A: 1.6m Mephisto optical observations
  16. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  17. GRB 250330A: VLT/FORS2 Optical Observations
  18. GRB 250330A: Prompt Swift-XRT position
  19. GRB 250329B: Swift-XRT afterglow detection
  20. GRB 250330A: Swift detection of a burst
  21. GRB 250329B: SVOM/C-GFT optical upper limit
  22. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  23. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  24. GRB250329A: REM optical afterglow detection
  25. GRB 250329B: GWAC-F50A optical upper limit
  26. GRB 250329A: Swift-XRT afterglow detection
  27. GRB 250328A: SVOM/VT optical observation
  28. GRB 250329A: Fading optical counterpart detection by LCO.
  29. GRB 250328A: SVOM/C-GFT optical upper limit
  30. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  31. GRB 250329A: VLT/X-shooter redshift z = 2.921
  32. GRB 250329A: SVOM/VT optical counterpart confirmation
  33. GRB 250329A: SVOM detection of a burst
  34. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  35. GRB 250327B: J-band observations with WINTER
  36. GRB 250327B: LCO optical counterpart detection
  37. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  38. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  39. GRB 250327B: CrAO and SAO RAS Optical Observations
  40. EP250315a: Pan-STARRS r and i-band imaging and photometry
  41. GRB 250327b: Liverpool Telescope optical observations
  42. GRB 250322A: GRANDMA/TNOT optical upper limits
  43. GRB 250327A: SVOM/VT upper limits on the XRT position
  44. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  45. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  46. GRB 250327B: Las Cumbres optical counterpart detection
  47. GRB 250327B: 1.6m Mephisto optical observations
  48. GRB 250327B: NOT spectroscopic redshift z = 3.035
  49. GRB 250327B: SVOM/VT optically bright counterpart
  50. GRB 250327B: SAO RAS optical candidate
  51. GRB 250327B: SVOM detection of a burst
  52. GRB 250327A: J-band observations with WINTER
  53. GRB 250327A: SVOM/VT optical candidate
  54. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  55. GRB 250327A: DDOTI Optical Observations
  56. GRB 250327A: COLIBRÍ optical upper limit
  57. IPN triangulation of GRB 250322B
  58. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  59. EP250321a: Mondy AZT-33IK Continued Optical Observations
  60. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  61. GRB 250322A: third epoch of NOT optical observations
  62. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  63. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  64. GRB 250322A: further NOT optical observations
  65. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  66. GRB 250322A: Swift/UVOT Upper Limits
  67. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  68. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  69. GRB 250321B: Swift-XRT observations
  70. EP250321a: TNOT Observation of Optical Counterpart
  71. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  72. GRB 250322A: VLT optical observations
  73. GRB 250322A: VLT near-infrared observations
  74. FRB 250316A: DDOTI Continued Optical Observations
  75. GRB 250322A: NOT optical upper limits
  76. GRB 250322A: Enhanced Swift-XRT position
  77. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  78. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  79. EP250321a: Liverpool Telescope optical follow-up
  80. EP250321a: Mondy AZT-33IK Optical Observations
  81. GRB 250322A: Swift detection of a short burst
  82. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  83. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP250321a: KAIT optical observations
  85. EP250321A: COLIBRÍ Continuing Optical Observations
  86. EP250321a: WFST optical observations
  87. EP250321a: Xinglong 216 decaying optical observations
  88. GRB 250321A: Swift-XRT refined Analysis
  89. EP 250321A: Optical counterpart detection by LCO.
  90. EP250321a: Kinder optical follow-up observations
  91. GRB 250321A: Swift/UVOT Upper Limits
  92. GRB 250320B: SVOM/GRM observation of a long burst
  93. EP250321a: LCO optical counterpart detection
  94. EP250321A: COLIBRÍ Optical Observations
  95. GRB 250320B: AstroSat CZTI detection
  96. EP250321a: REM optical/NIR afterglow detection
  97. EP250321a: TRT optical counterpart detection
  98. EP250321a: Einstein Probe detection of an X-ray transient
  99. GRB 250321A: GOTO optical upper limits
  100. GRB 250314A: Keck/NIRC2 J-band upper limit

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