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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"
  1. GRB 250306A: AstroSat CZTI detection
  2. Fermi trigger No 762963055: Global MASTER-Net observations report
  3. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  4. Swift GRB 250306A: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  6. GRB 250306A: Swift detection of a burst
  7. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  8. GRB250101A: Radio upper limits from VLA observations
  9. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  10. GRB 250305A: SVOM/GRM observation of a burst
  11. The EP-WXT trigger 01709132323 is likely a flaring star
  12. EP250304A: Upper limits from Fermi-GBM Observations
  13. Fermi GRB 250305A: Global MASTER-Net observations report
  14. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  15. GRB 250305A: Fermi GBM Final Real-time Localization
  16. EP250302a: Optical Observations at CrAO and SAO RAS
  17. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  18. EP 250304A: Optical counterpart detection by LCO
  19. EP250302A: 1.3m DFOT optical afterglow detection
  20. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  21. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  22. Konus-Wind detection of GRB 250222A
  23. EP250304a: REM NIR upper limits
  24. IPN triangulation of GRB 250222A
  25. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  26. EP250302a: Mondy Continued Optical Observations
  27. EP250304a: VLT/X-shooter redshift z = 0.200
  28. EP250304a: Swift-XRT detection of a fading X-ray source
  29. EP250304a: TRT optical counterpart detection
  30. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  31. EP250304a: Global MASTER-Net observations report
  32. EP250304a: Einstein Probe detection of an X-ray transient
  33. The EP-WXT trigger 01709132212 is not a real source
  34. EP250302a: SVOM/VT optical observation
  35. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  36. EP250302a: SAO RAS optical observations
  37. EP250302a : GIT optical follow-up
  38. EP250302a: VLT/X-shooter redshift confirmation
  39. EP250225a: the candidate optical counterpart is an AGN
  40. EP250302a: Kinder optical follow-up observations
  41. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  42. EP250302a: Swift/UVOT detection
  43. EP250302a: NUTTelA-TAO Early Measurments
  44. EP250302a: optical observation from the INAF Asiago Observatory
  45. EP250302a: REM NIR upper limits
  46. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  47. EP250302a: Mondy Observations and Optical Light Curve
  48. EP250302a: VLT/MUSE optical redshift z = 1.131
  49. INTEGRAL: end of scientific operations
  50. EP250302A: VLT near-infrared observations
  51. EP250302A: VLT/X-shooter tentative redshift
  52. EP250302a: OHP/T193 optical and spectroscopic observations
  53. EP250302a: Global MASTER-Net observations report
  54. EP250302a: Xinglong F60B optical observation
  55. EP250302a: Swift-XRT observations of a fading X-ray source
  56. EP250302a: Einstein Probe detection of an X-ray transient
  57. EP250302a: SVOM/C-GFT optical observations
  58. GRB 250226A: GRANDMA Optical Observations
  59. EP250302a: Montarrenti Observatory optical detection
  60. Fermi GRB 250302A: Global MASTER-Net observations report
  61. EP250302a: FTW optical and NIR detection
  62. EP250302a: Nanshan/HMT optical counterpart detection
  63. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 250302A: Fermi GBM Final Real-time Localization
  65. GRB 250228A: Fermi GBM Final Localization
  66. The EP-WXT trigger 01709132140 is likely a flaring star
  67. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  68. GRB 250225B: VLT near-infrared afterglow confirmation
  69. EP250228a: Optical observations with Kinder and Swift/UVOT
  70. Konus-Wind detection of GRB 250226A
  71. GRB 250225B: EIRSAT-1 GMOD Detection
  72. GRB 250226A: KAO Optical Upper Limit
  73. GRB 250226A: AbAO AS-32 Optical Upper Limit
  74. EP250227a: Global MASTER-Net observations report
  75. EP250223A: Upper limits from Fermi-GBM Observations
  76. EP250227a: TRT optical upper limit
  77. GRB 250225B: VLT/HAWKI near-infrared observations
  78. EP250227a: Optical upper limits with Kinder observations
  79. EP250227a: NOT optical observations
  80. EP250227a: Einstein Probe detected of a fast X-ray transient
  81. EP250228a: updates on the EP observations
  82. GRB 250226A: Fermi GBM Observation
  83. EP250225a: EP-FXT follow-up observation
  84. EP250223a: J band upper limit by SYSU 80cm telescope
  85. EP250228a: Swift/XRT localisation
  86. EP250228a: Global MASTER-Net observations report
  87. EP250228a: Einstein Probe detection of an X-ray transient
  88. GRB 250226A / EP250226a: LCO detection of the afterglow
  89. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  91. GRB 250225B: VLT/Xshooter imaging
  92. GRB 250205A / EP250205A: further radio observations with the VLA
  93. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  94. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  95. GRB 250225B: INTEGRAL SPI-ACS detection
  96. EP250225a: NOT optical candidate counterpart
  97. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  98. EP250226a / GRB 250226A: SVOM/VT optical observations
  99. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  100. EP250225a: TRT optical upper limits

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