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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

3363 results found.

  1. EP250428b: Global MASTER-Net observations report
  2. GRB 250424A: Swift-BAT refined analysis
  3. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 250424A: BlackGEM optical afterglow detection
  5. IceCube Alert 250421.71: Global MASTER-Net observations report
  6. GRB 250419A: LCO optical observation
  7. GRB 250419A: AKO Optical Afterglow Detection
  8. SVOM/sb25041603 is not a GRB
  9. EP250404a: Nanshan 0.43m Telescope optical observatios
  10. Fermi trigger No 766173972: Global MASTER-Net observations report
  11. Fermi GRB 250407A: Global MASTER-Net observations report
  12. IceCube Alert 250406.95: Global MASTER-Net observations report
  13. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  14. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  15. Fermi GRB 250404A: Global MASTER-Net observations report
  16. GRB 250403A: Montarrenti Observatory optical detection
  17. EP250404a: Global MASTER-Net observations report
  18. GRB 250402A: Fermi GBM Observation
  19. Fermi GRB 250331E: Global MASTER-Net observations report
  20. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  21. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  22. GRB 250331A: MAXI/GSC detection
  23. Fermi GRB 250330B: Global MASTER-Net observations report
  24. IceCube Alert 250330.35: Global MASTER-Net observations report
  25. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  26. GRB 250327B: LCO optical counterpart detection
  27. IPN triangulation of GRB 250322B
  28. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  29. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  30. EP250321a: Kinder optical follow-up observations
  31. Fermi GRB 250320B: Global MASTER-Net observations report
  32. EP250321a: BOOTES-5/JGT optical afterglow detection
  33. EP250321a: TRT optical counterpart detection
  34. Swift GRB 250321A: Global MASTER-Net observations report
  35. GRB 250309B/AT2025dws: further ATCA observations
  36. GRB 250316A: Fermi GBM Final Real-time Localization
  37. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  38. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  39. Fermi GRB 250313A: Global MASTER-Net observations report
  40. EP250311a/GRB 250311A: EP-FXT follow-up observation
  41. Fermi GRB 250312B: Global MASTER-Net observations report
  42. GRB 250312B: Fermi GBM Final Localization
  43. GRB 241228A: VIRT Optical Upper Limit
  44. GRB 250311A: Swift-XRT observations
  45. GRB 250311A/EP250311a: TRT optical upper limit
  46. GRB 250311A: Tiled Swift observations
  47. EP250311a/GRB 250311A: EP-WXT detection
  48. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  49. IceCube Alert 250309.32: Global MASTER-Net observations report
  50. EP250308a: Global MASTER-Net observations report
  51. EP250308a: Einstein Probe detection of an X-ray transient
  52. GRB 250307A: Fermi GBM Final Real-time Localization
  53. GRB 250306A: Swift-BAT refined analysis
  54. GRB 250305A: AstroSat CZTI detection
  55. Fermi trigger No 762963055: Global MASTER-Net observations report
  56. GRB 250305A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  58. EP250302a: Montarrenti Observatory optical detection
  59. Fermi GRB 250302A: Global MASTER-Net observations report
  60. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  61. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  62. EP250226a / GRB 250226A: TRT optical counterpart observation
  63. GRB 250226A: Fermi GBM Final Real-time Localization
  64. Fermi GRB 250225A: Global MASTER-Net observations report
  65. GRB 250202B: VZLUSAT-2 detection
  66. EP250220a: EP-FXT follow-up observations
  67. EP250220a: 1.6m Mephisto observations
  68. SVOM trigger sb25022102 is not an astrophysical event
  69. SVOM/sb25022102: SVOM detection of an X-ray transient
  70. GRB 250221A: Swift detection of a burst with an optical counterpart
  71. Swift GRB250221.15: Global MASTER-Net observations report
  72. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  73. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  74. Fermi GRB 250217A: Global MASTER-Net observations report
  75. EP250215a: Global MASTER-Net observations report
  76. Fermi GRB 250212A: Global MASTER-Net observations report
  77. Fermi trigger No 760945500: Global MASTER-Net observations report
  78. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  79. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  80. EP250207b: Global MASTER-Net observations report
  81. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  82. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  83. IceCube Alert 250207.09: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  85. GRB 250207B: Swift-XRT observations
  86. GRB 250207B: Tiled Swift observations
  87. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  88. GRB 250207B: MAXI/GSC detection
  89. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  90. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  91. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  92. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  93. Konus-Wind detection of GRB 250202B
  94. IPN triangulation of GRB 250202B
  95. GRB 250202B: NuSTAR detection of the prompt emission
  96. GRB 250202B: Fermi GBM Detection
  97. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  98. GRB 250202B: Fermi GBM Final Real-time Localization
  99. GRB 250129A: 1.3m DFOT Optical observations
  100. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations

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