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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"

20954 results found.

  1. EP250311a/GRB 250311A: EP-WXT detection
  2. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  3. GRB 250309B / AT2025dws: further SAO RAS optical observations
  4. IceCube-250309A: Upper limits from Fermi-GBM Observations
  5. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  6. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  7. GRB 250309B / IceCube-250309A: GECAM-B observations
  8. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  9. GRB 250309B / AT2025dws: SAO RAS optical observations
  10. GRB 250309B / AT2025dws: Swift-UVOT detection
  11. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  12. Fermi GRB 250309B: Global MASTER-Net observations report
  13. Fermi GRB 250309A: Global MASTER-Net observations report
  14. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  15. IceCube-250309A: No candidates from the Zwicky Transient Facility
  16. Fermi-LAT gamma-ray observations of IceCube-250309A
  17. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  18. GRB 230509B: Tiled Swift observations
  19. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  20. IceCube Alert 250309.32: Global MASTER-Net observations report
  21. EP250308a: Global MASTER-Net observations report
  22. EP250308a: GSP optical upper limit
  23. EP250308a: FTW optical and NIR upper limits
  24. EP250308a: Einstein Probe detection of an X-ray transient
  25. Fermi GRB 250307A: Global MASTER-Net observations report
  26. EP250304a: MeerKAT detection of a possible radio counterpart
  27. EP250302a:Xinglong optical observations
  28. Fermi trigger No 762963055: Global MASTER-Net observations report
  29. Swift GRB 250306A: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  31. GRB250101A: Radio upper limits from VLA observations
  32. EP250304A: Upper limits from Fermi-GBM Observations
  33. Fermi GRB 250305A: Global MASTER-Net observations report
  34. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  35. EP250302a: Optical Observations at CrAO and SAO RAS
  36. EP 250304A: Optical counterpart detection by LCO
  37. EP250302A: 1.3m DFOT optical afterglow detection
  38. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  39. EP250304a: REM NIR upper limits
  40. EP250302a: Mondy Continued Optical Observations
  41. EP250304a: TRT optical counterpart detection
  42. EP250304a: Global MASTER-Net observations report
  43. EP250302a: SVOM/VT optical observation
  44. EP250302a: SAO RAS optical observations
  45. EP250225a: the candidate optical counterpart is an AGN
  46. EP250302a: Kinder optical follow-up observations
  47. EP250302a: NUTTelA-TAO Early Measurments
  48. EP250302a: REM NIR upper limits
  49. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  50. EP250302a: Mondy Observations and Optical Light Curve
  51. EP250302a: VLT/MUSE optical redshift z = 1.131
  52. EP250302A: VLT near-infrared observations
  53. EP250302A: VLT/X-shooter tentative redshift
  54. EP250302a: OHP/T193 optical and spectroscopic observations
  55. EP250302a: Global MASTER-Net observations report
  56. EP250302a: Xinglong F60B optical observation
  57. EP250302a: Swift-XRT observations of a fading X-ray source
  58. EP250302a: Einstein Probe detection of an X-ray transient
  59. EP250302a: SVOM/C-GFT optical observations
  60. GRB 250226A: GRANDMA Optical Observations
  61. EP250302a: Montarrenti Observatory optical detection
  62. Fermi GRB 250302A: Global MASTER-Net observations report
  63. EP250302a: FTW optical and NIR detection
  64. EP250302a: Nanshan/HMT optical counterpart detection
  65. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  66. GRB 250225B: VLT near-infrared afterglow confirmation
  67. EP250228a: Optical observations with Kinder and Swift/UVOT
  68. GRB 250226A: KAO Optical Upper Limit
  69. GRB 250226A: AbAO AS-32 Optical Upper Limit
  70. EP250227a: Global MASTER-Net observations report
  71. EP250223A: Upper limits from Fermi-GBM Observations
  72. EP250227a: TRT optical upper limit
  73. GRB 250225B: VLT/HAWKI near-infrared observations
  74. EP250227a: Optical upper limits with Kinder observations
  75. EP250227a: NOT optical observations
  76. EP250228a: updates on the EP observations
  77. EP250223a: J band upper limit by SYSU 80cm telescope
  78. EP250228a: Global MASTER-Net observations report
  79. GRB 250226A / EP250226a: LCO detection of the afterglow
  80. GRB 250225B: VLT/Xshooter imaging
  81. GRB 250205A / EP250205A: further radio observations with the VLA
  82. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  83. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  84. GRB 250225B: INTEGRAL SPI-ACS detection
  85. EP250225a: NOT optical candidate counterpart
  86. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  87. EP250226a / GRB 250226A: SVOM/VT optical observations
  88. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  89. EP250225a: TRT optical upper limits
  90. EP250226a/GRB 250226A: 1.6m Mephisto observations
  91. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  92. EP250226a/GRB 250226A: Kinder optical follow-up observations
  93. Fermi GRB 250226B: Global MASTER-Net observations report
  94. GRB 250221A: ATCA Detections and Upper Limits
  95. GRB 250225B: REM NIR upper limits
  96. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  97. GRB 250225B: VLT optical and near-infrared candidate counterpart
  98. GRB 250225B: VLT/FORS2 candidate optical afterglow
  99. GRB 250221A: EP-FXT detection of the X-ray afterglow
  100. EP250226a/GRB 250226A: GSP detects optical counterpart

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