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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. Fermi GRB 250330B: Global MASTER-Net observations report
  2. GRB 250330B: Fermi GBM Final Real-time Localization
  3. Fermi GRB 250330A: Global MASTER-Net observations report
  4. GRB 250330A: BOOTES-7 early optical upper limit
  5. GRB 250330A: Swift/UVOT Upper Limits
  6. GRB 250330A: Swift-XRT afterglow detection
  7. GRB 250328A: 1.6m Mephisto optical observations
  8. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  9. GRB 250330A: Fermi GBM Final Localization
  10. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  11. IceCube Alert 250330.35: Global MASTER-Net observations report
  12. GRB 250330A: VLT/FORS2 Optical Observations
  13. GRB 250330A: Prompt Swift-XRT position
  14. GRB 250329B: Swift-XRT afterglow detection
  15. GRB 250330A: Swift detection of a burst
  16. Swift GRB250330.26: Global MASTER-Net observations report
  17. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  18. GRB 250329B: SVOM/C-GFT optical upper limit
  19. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  20. GRB 250327B: ALMA detection
  21. GRB 250327B: VLA detection
  22. GRB 250329B: SVOM/VT optical upper limit
  23. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  24. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  25. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  26. GRB250329A: REM optical afterglow detection
  27. GRB 250329B: GWAC-F50A optical upper limit
  28. GRB 250329B: SVOM detection of a faint transient
  29. GRB 250329A: Swift-XRT afterglow detection
  30. GRB 250328A: SVOM/VT optical observation
  31. GRB 250329A: Fading optical counterpart detection by LCO.
  32. GRB 250328A: SVOM/C-GFT optical upper limit
  33. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  34. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  35. GRB 250329A: VLT/X-shooter redshift z = 2.921
  36. GRB 250329A: SVOM/VT optical counterpart confirmation
  37. GRB 250329A: SVOM detection of a burst
  38. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  39. GRB 250327B: J-band observations with WINTER
  40. GRB 250327B: MASTER detection of OT rebrightening
  41. GRB 250327B: LCO optical counterpart detection
  42. GRB 250328A: GWAC-F50A optical upper limit
  43. GRB 250328A: SVOM detection of a burst
  44. FRB 20250316A: FTW optical observations
  45. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  46. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  47. GRB 250327B: CrAO and SAO RAS Optical Observations
  48. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  49. GRB 250327B: further optical observations by LCOGT
  50. EP250315a: Pan-STARRS r and i-band imaging and photometry
  51. GRB 250327b: Liverpool Telescope optical observations
  52. GRB 250322A: GRANDMA/TNOT optical upper limits
  53. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  54. GRB 250327A: SVOM/VT upper limits on the XRT position
  55. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  56. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  57. GRB 250327B: Las Cumbres optical counterpart detection
  58. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  59. GRB 250327B: 1.6m Mephisto optical observations
  60. GRB 250327B: NOT spectroscopic redshift z = 3.035
  61. GRB 250327A: Swift-XRT refined Analysis
  62. GRB 250327B: GOTO optical counterpart detection
  63. GRB 250327B: SVOM/VT optically bright counterpart
  64. GRB 250327B: SAO RAS optical candidate
  65. GRB 250327B: SVOM detection of a burst
  66. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  67. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  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: Fermi GBM observation
  72. Fermi GRB 250327A: Global MASTER-Net observations report
  73. Swift GRB 250327A: Global MASTER-Net observations report
  74. GRB 250327A: DDOTI Optical Observations
  75. GRB 250327A: COLIBRÍ optical upper limit
  76. GRB 250327A: Swift detection of a burst
  77. GRB 250327A: Fermi GBM Final Real-time Localization
  78. Fermi trigger No 764700395: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  80. Konus-Wind detection of GRB 250322A (short)
  81. IPN triangulation of GRB 250322B
  82. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  83. EP250321a: Mondy AZT-33IK Continued Optical Observations
  84. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  85. GRB 250322A: third epoch of NOT optical observations
  86. GRB 250322A: Swift-BAT refined analysis
  87. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  88. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  89. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  90. GRB 250322A: further NOT optical observations
  91. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  92. GRB 250322A: Swift/UVOT Upper Limits
  93. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  94. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  95. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  96. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  97. GRB 250321B: Swift-XRT observations
  98. GRB 250322A: Swift-XRT refined Analysis
  99. EP250321a: TNOT Observation of Optical Counterpart
  100. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)

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