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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"

20957 results found.

  1. GRB 250311A/EP250311a: TRT optical upper limit
  2. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  3. GRB 250311A: Tiled Swift observations
  4. EP250311a/GRB 250311A: EP-WXT detection
  5. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  6. GRB 250309B / AT2025dws: further SAO RAS optical observations
  7. IceCube-250309A: Upper limits from Fermi-GBM Observations
  8. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  9. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  10. GRB 250309B / IceCube-250309A: GECAM-B observations
  11. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  12. GRB 250309B / AT2025dws: SAO RAS optical observations
  13. GRB 250309B / AT2025dws: Swift-UVOT detection
  14. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  15. Fermi GRB 250309B: Global MASTER-Net observations report
  16. Fermi GRB 250309A: Global MASTER-Net observations report
  17. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  18. IceCube-250309A: No candidates from the Zwicky Transient Facility
  19. Fermi-LAT gamma-ray observations of IceCube-250309A
  20. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  21. GRB 230509B: Tiled Swift observations
  22. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  23. IceCube Alert 250309.32: Global MASTER-Net observations report
  24. EP250308a: Global MASTER-Net observations report
  25. EP250308a: GSP optical upper limit
  26. EP250308a: FTW optical and NIR upper limits
  27. EP250308a: Einstein Probe detection of an X-ray transient
  28. Fermi GRB 250307A: Global MASTER-Net observations report
  29. EP250304a: MeerKAT detection of a possible radio counterpart
  30. EP250302a:Xinglong optical observations
  31. Fermi trigger No 762963055: Global MASTER-Net observations report
  32. Swift GRB 250306A: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  34. GRB250101A: Radio upper limits from VLA observations
  35. EP250304A: Upper limits from Fermi-GBM Observations
  36. Fermi GRB 250305A: Global MASTER-Net observations report
  37. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  38. EP250302a: Optical Observations at CrAO and SAO RAS
  39. EP 250304A: Optical counterpart detection by LCO
  40. EP250302A: 1.3m DFOT optical afterglow detection
  41. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP250304a: REM NIR upper limits
  43. EP250302a: Mondy Continued Optical Observations
  44. EP250304a: TRT optical counterpart detection
  45. EP250304a: Global MASTER-Net observations report
  46. EP250302a: SVOM/VT optical observation
  47. EP250302a: SAO RAS optical observations
  48. EP250225a: the candidate optical counterpart is an AGN
  49. EP250302a: Kinder optical follow-up observations
  50. EP250302a: NUTTelA-TAO Early Measurments
  51. EP250302a: REM NIR upper limits
  52. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  53. EP250302a: Mondy Observations and Optical Light Curve
  54. EP250302a: VLT/MUSE optical redshift z = 1.131
  55. EP250302A: VLT near-infrared observations
  56. EP250302A: VLT/X-shooter tentative redshift
  57. EP250302a: OHP/T193 optical and spectroscopic observations
  58. EP250302a: Global MASTER-Net observations report
  59. EP250302a: Xinglong F60B optical observation
  60. EP250302a: Swift-XRT observations of a fading X-ray source
  61. EP250302a: Einstein Probe detection of an X-ray transient
  62. EP250302a: SVOM/C-GFT optical observations
  63. GRB 250226A: GRANDMA Optical Observations
  64. EP250302a: Montarrenti Observatory optical detection
  65. Fermi GRB 250302A: Global MASTER-Net observations report
  66. EP250302a: FTW optical and NIR detection
  67. EP250302a: Nanshan/HMT optical counterpart detection
  68. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  69. GRB 250225B: VLT near-infrared afterglow confirmation
  70. EP250228a: Optical observations with Kinder and Swift/UVOT
  71. GRB 250226A: KAO Optical Upper Limit
  72. GRB 250226A: AbAO AS-32 Optical Upper Limit
  73. EP250227a: Global MASTER-Net observations report
  74. EP250223A: Upper limits from Fermi-GBM Observations
  75. EP250227a: TRT optical upper limit
  76. GRB 250225B: VLT/HAWKI near-infrared observations
  77. EP250227a: Optical upper limits with Kinder observations
  78. EP250227a: NOT optical observations
  79. EP250228a: updates on the EP observations
  80. EP250223a: J band upper limit by SYSU 80cm telescope
  81. EP250228a: Global MASTER-Net observations report
  82. GRB 250226A / EP250226a: LCO detection of the afterglow
  83. GRB 250225B: VLT/Xshooter imaging
  84. GRB 250205A / EP250205A: further radio observations with the VLA
  85. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  86. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  87. GRB 250225B: INTEGRAL SPI-ACS detection
  88. EP250225a: NOT optical candidate counterpart
  89. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  90. EP250226a / GRB 250226A: SVOM/VT optical observations
  91. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  92. EP250225a: TRT optical upper limits
  93. EP250226a/GRB 250226A: 1.6m Mephisto observations
  94. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  95. EP250226a/GRB 250226A: Kinder optical follow-up observations
  96. Fermi GRB 250226B: Global MASTER-Net observations report
  97. GRB 250221A: ATCA Detections and Upper Limits
  98. GRB 250225B: REM NIR upper limits
  99. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  100. GRB 250225B: VLT optical and near-infrared candidate counterpart

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