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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"

19089 results found.

  1. GRB 250402B: AstroSat CZTI detection of a short burst
  2. GRB 250402A: SVOM/VT optical counterpart
  3. GRB 250402A: SVOM detection of a burst
  4. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  5. GRB 250329B: Swift/UVOT Upper Limit
  6. GRB 250329A: Swift/UVOT Upper Limit
  7. GRB 250327B: Swift/UVOT Detection
  8. GRB 250327A: Swift/UVOT Upper Limits
  9. GRB 250331E: SVOM/GRM observation
  10. GRB 250327B: Kilonova-Catcher Observations
  11. GRB 250331C: Swift/UVOT Upper Limits
  12. GRB 250331B: Swift/UVOT Upper Limits
  13. GRB 250328A: AbAO AS-32 Optical Observations
  14. GRB 250219A: NOT candidate host galaxy detection
  15. GRB 250330B: SVOM/GRM observation of a short burst
  16. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  17. GRB 250331D: Swift ToO observations
  18. GRB 250331C: Enhanced Swift-XRT position
  19. GRB 250331B: Enhanced Swift-XRT position
  20. GRB 250330A: VLT/FORS2 Afterglow Detection
  21. GRB20250327B: 45th Parallel Observatory upper limit
  22. GRB 250328A: Swift/UVOT Detection
  23. GRB 250328A: Swift-XRT refined Analysis
  24. GRB 250330A: Fermi GBM Observation
  25. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  26. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  27. GRB 250331C: Swift detection of a burst
  28. GRB 250331B: Swift detection of a burst
  29. SVOM/sb25033102: SVOM detection of an X-ray transient
  30. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  31. GRB 250330A: Swift/UVOT Upper Limits
  32. GRB 250330A: Swift-XRT afterglow detection
  33. GRB 250328A: 1.6m Mephisto optical observations
  34. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  35. GRB 250330A: VLT/FORS2 Optical Observations
  36. GRB 250329B: Swift-XRT afterglow detection
  37. GRB 250330A: Swift detection of a burst
  38. GRB 250329B: SVOM/C-GFT optical upper limit
  39. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  40. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  41. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  42. GRB250329A: REM optical afterglow detection
  43. GRB 250329B: SVOM detection of a faint transient
  44. GRB 250329A: Swift-XRT afterglow detection
  45. GRB 250328A: SVOM/VT optical observation
  46. GRB 250329A: Fading optical counterpart detection by LCO.
  47. GRB 250328A: SVOM/C-GFT optical upper limit
  48. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  49. GRB 250329A: SVOM/VT optical counterpart confirmation
  50. GRB 250329A: SVOM detection of a burst
  51. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  52. GRB 250327B: J-band observations with WINTER
  53. GRB 250327B: LCO optical counterpart detection
  54. GRB 250328A: SVOM detection of a burst
  55. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  56. GRB 250327B: CrAO and SAO RAS Optical Observations
  57. GRB 250327b: Liverpool Telescope optical observations
  58. GRB 250322A: GRANDMA/TNOT optical upper limits
  59. GRB 250327A: SVOM/VT upper limits on the XRT position
  60. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  61. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  62. GRB 250327B: Las Cumbres optical counterpart detection
  63. GRB 250327B: 1.6m Mephisto optical observations
  64. GRB 250327B: SVOM/VT optically bright counterpart
  65. GRB 250327B: SAO RAS optical candidate
  66. GRB 250327B: SVOM detection of a burst
  67. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  68. GRB 250327A: J-band observations with WINTER
  69. GRB 250327A: SVOM/VT optical candidate
  70. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  71. GRB 250327A: DDOTI Optical Observations
  72. GRB 250327A: COLIBRÍ optical upper limit
  73. IPN triangulation of GRB 250322B
  74. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  75. EP250321a: Mondy AZT-33IK Continued Optical Observations
  76. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  77. GRB 250322A: third epoch of NOT optical observations
  78. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  79. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  80. GRB 250322A: further NOT optical observations
  81. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  82. GRB 250322A: Swift/UVOT Upper Limits
  83. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  84. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  85. GRB 250321B: Swift-XRT observations
  86. EP250321a: TNOT Observation of Optical Counterpart
  87. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  88. SVOM/sb25032302: SVOM detection of a long X-ray transient
  89. GRB250322A: STEP/T80S optical limits
  90. GRB 250322A: VLT optical observations
  91. GRB 250322A: VLT near-infrared observations
  92. FRB 250316A: DDOTI Continued Optical Observations
  93. GRB 250322A: NOT optical upper limits
  94. GRB 250322A: Enhanced Swift-XRT position
  95. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  96. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  97. EP250321a: Liverpool Telescope optical follow-up
  98. EP250321a: Mondy AZT-33IK Optical Observations
  99. GRB 250322A: Swift detection of a short burst
  100. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe

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