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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').
  1. GRB 250320C : SVOM detection of a burst through offline search
  2. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  3. GRB 250329B: Swift-XRT confirmation of fading
  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. Fermi-LAT gamma-ray observations of IceCube-250330A
  9. SVOM/sb25033102 is a false trigger
  10. GRB 250330A: Fermi GBM Observation
  11. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  12. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  13. GRB 250331D: Fermi GBM Final Real-time Localization
  14. GRB 250331C: Prompt enhanced Swift-XRT position
  15. GRB 250331C: Swift detection of a burst
  16. GRB 250331B: Swift detection of a burst
  17. GRB 250330A: SVOM/VT optical upper limit
  18. GRB 250331A: MAXI/GSC detection
  19. SVOM/sb25033102: SVOM detection of an X-ray transient
  20. GRB 250314A: VLA detection
  21. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  22. Fermi GRB 250330B: Global MASTER-Net observations report
  23. GRB 250330B: Fermi GBM Final Real-time Localization
  24. Fermi GRB 250330A: Global MASTER-Net observations report
  25. GRB 250330A: BOOTES-7 early optical upper limit
  26. GRB 250330A: Swift/UVOT Upper Limits
  27. GRB 250330A: Swift-XRT afterglow detection
  28. GRB 250328A: 1.6m Mephisto optical observations
  29. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  30. GRB 250330A: Fermi GBM Final Localization
  31. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  32. IceCube Alert 250330.35: Global MASTER-Net observations report
  33. GRB 250330A: VLT/FORS2 Optical Observations
  34. GRB 250330A: Prompt Swift-XRT position
  35. GRB 250329B: Swift-XRT afterglow detection
  36. GRB 250330A: Swift detection of a burst
  37. Swift GRB250330.26: Global MASTER-Net observations report
  38. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  39. GRB 250329B: SVOM/C-GFT optical upper limit
  40. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  41. GRB 250327B: ALMA detection
  42. GRB 250327B: VLA detection
  43. GRB 250329B: SVOM/VT optical upper limit
  44. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  45. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  46. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  47. GRB250329A: REM optical afterglow detection
  48. GRB 250329B: GWAC-F50A optical upper limit
  49. GRB 250329B: SVOM detection of a faint transient
  50. GRB 250329A: Swift-XRT afterglow detection
  51. GRB 250328A: SVOM/VT optical observation
  52. GRB 250329A: Fading optical counterpart detection by LCO.
  53. GRB 250328A: SVOM/C-GFT optical upper limit
  54. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  55. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  56. GRB 250329A: VLT/X-shooter redshift z = 2.921
  57. GRB 250329A: SVOM/VT optical counterpart confirmation
  58. GRB 250329A: SVOM detection of a burst
  59. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  60. GRB 250327B: J-band observations with WINTER
  61. GRB 250327B: MASTER detection of OT rebrightening
  62. GRB 250327B: LCO optical counterpart detection
  63. GRB 250328A: GWAC-F50A optical upper limit
  64. GRB 250328A: SVOM detection of a burst
  65. FRB 20250316A: FTW optical observations
  66. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  67. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  68. GRB 250327B: CrAO and SAO RAS Optical Observations
  69. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  70. GRB 250327B: further optical observations by LCOGT
  71. EP250315a: Pan-STARRS r and i-band imaging and photometry
  72. GRB 250327b: Liverpool Telescope optical observations
  73. GRB 250322A: GRANDMA/TNOT optical upper limits
  74. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  75. GRB 250327A: SVOM/VT upper limits on the XRT position
  76. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  77. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  78. GRB 250327B: Las Cumbres optical counterpart detection
  79. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  80. GRB 250327B: 1.6m Mephisto optical observations
  81. GRB 250327B: NOT spectroscopic redshift z = 3.035
  82. GRB 250327A: Swift-XRT refined Analysis
  83. GRB 250327B: GOTO optical counterpart detection
  84. GRB 250327B: SVOM/VT optically bright counterpart
  85. GRB 250327B: SAO RAS optical candidate
  86. GRB 250327B: SVOM detection of a burst
  87. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  88. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  89. GRB 250327A: J-band observations with WINTER
  90. GRB 250327A: SVOM/VT optical candidate
  91. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  92. GRB 250327A: Fermi GBM observation
  93. Fermi GRB 250327A: Global MASTER-Net observations report
  94. Swift GRB 250327A: Global MASTER-Net observations report
  95. GRB 250327A: DDOTI Optical Observations
  96. GRB 250327A: COLIBRÍ optical upper limit
  97. GRB 250327A: Swift detection of a burst
  98. GRB 250327A: Fermi GBM Final Real-time Localization
  99. Fermi trigger No 764700395: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S250326y: Updated Sky localization

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