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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"

15717 results found.

  1. GRB 250402A: SVOM/VT optical counterpart
  2. GRB 250402A: SVOM detection of a burst
  3. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  4. GRB 250314A: ALMA detection
  5. GRB 250329A: Swift/UVOT Upper Limit
  6. GRB 250327B: Swift/UVOT Detection
  7. GRB 250327A: Swift/UVOT Upper Limits
  8. GRB 250331E: SVOM/GRM observation
  9. GRB 250327B: Kilonova-Catcher Observations
  10. GRB250331D: AbAO optical 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. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  17. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  18. GRB 250329B: CAHA 2.2m telescope optical limit
  19. GRB20250327B: 45th Parallel Observatory upper limit
  20. GRB 250328A: Swift-XRT refined Analysis
  21. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  22. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  23. GRB 250330A: SVOM/VT optical upper limit
  24. GRB 250314A: VLA detection
  25. GRB 250330A: BOOTES-7 early optical upper limit
  26. GRB 250330A: Swift/UVOT Upper Limits
  27. GRB 250328A: 1.6m Mephisto optical observations
  28. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  29. GRB 250330A: VLT/FORS2 Optical Observations
  30. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  31. GRB 250329B: SVOM/C-GFT optical upper limit
  32. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  33. GRB 250327B: ALMA detection
  34. GRB 250327B: VLA detection
  35. GRB 250329B: SVOM/VT optical upper limit
  36. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  37. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  38. GRB250329A: REM optical afterglow detection
  39. GRB 250329B: GWAC-F50A optical upper limit
  40. GRB 250329A: Swift-XRT afterglow detection
  41. GRB 250328A: SVOM/VT optical observation
  42. GRB 250329A: Fading optical counterpart detection by LCO.
  43. GRB 250328A: SVOM/C-GFT optical upper limit
  44. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  45. GRB 250329A: VLT/X-shooter redshift z = 2.921
  46. GRB 250329A: SVOM/VT optical counterpart confirmation
  47. GRB 250329A: SVOM detection of a burst
  48. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  49. GRB 250327B: J-band observations with WINTER
  50. GRB 250327B: MASTER detection of OT rebrightening
  51. GRB 250327B: LCO optical counterpart detection
  52. GRB 250328A: GWAC-F50A optical upper limit
  53. FRB 20250316A: FTW optical observations
  54. GRB 250327B: CrAO and SAO RAS Optical Observations
  55. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  56. GRB 250327B: further optical observations by LCOGT
  57. EP250315a: Pan-STARRS r and i-band imaging and photometry
  58. GRB 250327b: Liverpool Telescope optical observations
  59. GRB 250322A: GRANDMA/TNOT optical upper limits
  60. GRB 250327B: Las Cumbres optical counterpart detection
  61. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  62. GRB 250327B: 1.6m Mephisto optical observations
  63. GRB 250327B: NOT spectroscopic redshift z = 3.035
  64. GRB 250327B: GOTO optical counterpart detection
  65. GRB 250327B: SVOM/VT optically bright counterpart
  66. GRB 250327B: SAO RAS optical candidate
  67. GRB 250327B: SVOM detection of a burst
  68. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  69. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  70. GRB 250327A: SVOM/VT optical candidate
  71. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  72. GRB 250327A: DDOTI Optical Observations
  73. GRB 250327A: COLIBRÍ optical upper limit
  74. EP250321a: Mondy AZT-33IK Continued Optical Observations
  75. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  76. GRB 250322A: third epoch of NOT optical observations
  77. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  78. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  79. GRB 250322A: further NOT optical observations
  80. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  81. GRB 250322A: Swift/UVOT Upper Limits
  82. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  83. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  84. EP250321a: TNOT Observation of Optical Counterpart
  85. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  86. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  87. GRB250322A: STEP/T80S optical limits
  88. GRB 250322A: Gemini-South optical observations
  89. GRB 250322A: VLT optical observations
  90. FRB 250316A: DDOTI Continued Optical Observations
  91. GRB 250322A: NOT optical upper limits
  92. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  93. GRB 250322A: MASTER optical observation
  94. EP250321a: Liverpool Telescope optical follow-up
  95. EP250321a: Mondy AZT-33IK Optical Observations
  96. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  97. EP250321a: KAIT optical observations
  98. EP250321A: COLIBRÍ Continuing Optical Observations
  99. EP250321a: WFST optical observations
  100. EP250321a: Xinglong 216 decaying optical observations

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