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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"

44271 results found.

  1. Fermi trigger No 762963055: Global MASTER-Net observations report
  2. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  3. Swift GRB 250306A: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  5. GRB 250306A: Swift detection of a burst
  6. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  7. GRB250101A: Radio upper limits from VLA observations
  8. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  9. GRB 250305A: SVOM/GRM observation of a burst
  10. The EP-WXT trigger 01709132323 is likely a flaring star
  11. EP250304A: Upper limits from Fermi-GBM Observations
  12. Fermi GRB 250305A: Global MASTER-Net observations report
  13. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  14. GRB 250305A: Fermi GBM Final Real-time Localization
  15. EP250302a: Optical Observations at CrAO and SAO RAS
  16. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  17. EP 250304A: Optical counterpart detection by LCO
  18. EP250302A: 1.3m DFOT optical afterglow detection
  19. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  20. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  21. Konus-Wind detection of GRB 250222A
  22. EP250304a: REM NIR upper limits
  23. IPN triangulation of GRB 250222A
  24. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  25. EP250302a: Mondy Continued Optical Observations
  26. EP250304a: VLT/X-shooter redshift z = 0.200
  27. EP250304a: Swift-XRT detection of a fading X-ray source
  28. EP250304a: TRT optical counterpart detection
  29. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  30. EP250304a: Global MASTER-Net observations report
  31. EP250304a: Einstein Probe detection of an X-ray transient
  32. The EP-WXT trigger 01709132212 is not a real source
  33. EP250302a: SVOM/VT optical observation
  34. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  35. EP250302a: SAO RAS optical observations
  36. EP250302a : GIT optical follow-up
  37. EP250302a: VLT/X-shooter redshift confirmation
  38. EP250225a: the candidate optical counterpart is an AGN
  39. EP250302a: Kinder optical follow-up observations
  40. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  41. EP250302a: Swift/UVOT detection
  42. EP250302a: NUTTelA-TAO Early Measurments
  43. EP250302a: optical observation from the INAF Asiago Observatory
  44. EP250302a: REM NIR upper limits
  45. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  46. EP250302a: Mondy Observations and Optical Light Curve
  47. EP250302a: VLT/MUSE optical redshift z = 1.131
  48. INTEGRAL: end of scientific operations
  49. EP250302A: VLT near-infrared observations
  50. EP250302A: VLT/X-shooter tentative redshift
  51. EP250302a: OHP/T193 optical and spectroscopic observations
  52. EP250302a: Global MASTER-Net observations report
  53. EP250302a: Xinglong F60B optical observation
  54. EP250302a: Swift-XRT observations of a fading X-ray source
  55. EP250302a: Einstein Probe detection of an X-ray transient
  56. EP250302a: SVOM/C-GFT optical observations
  57. GRB 250226A: GRANDMA Optical Observations
  58. EP250302a: Montarrenti Observatory optical detection
  59. Fermi GRB 250302A: Global MASTER-Net observations report
  60. EP250302a: FTW optical and NIR detection
  61. EP250302a: Nanshan/HMT optical counterpart detection
  62. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  63. GRB 250302A: Fermi GBM Final Real-time Localization
  64. GRB 250228A: Fermi GBM Final Localization
  65. The EP-WXT trigger 01709132140 is likely a flaring star
  66. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  67. GRB 250225B: VLT near-infrared afterglow confirmation
  68. EP250228a: Optical observations with Kinder and Swift/UVOT
  69. Konus-Wind detection of GRB 250226A
  70. GRB 250225B: EIRSAT-1 GMOD Detection
  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. EP250227a: Einstein Probe detected of a fast X-ray transient
  80. EP250228a: updates on the EP observations
  81. GRB 250226A: Fermi GBM Observation
  82. EP250225a: EP-FXT follow-up observation
  83. EP250223a: J band upper limit by SYSU 80cm telescope
  84. EP250228a: Swift/XRT localisation
  85. EP250228a: Global MASTER-Net observations report
  86. EP250228a: Einstein Probe detection of an X-ray transient
  87. GRB 250226A / EP250226a: LCO detection of the afterglow
  88. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  89. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  90. GRB 250225B: VLT/Xshooter imaging
  91. GRB 250205A / EP250205A: further radio observations with the VLA
  92. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  93. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  94. GRB 250225B: INTEGRAL SPI-ACS detection
  95. EP250225a: NOT optical candidate counterpart
  96. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  97. EP250226a / GRB 250226A: SVOM/VT optical observations
  98. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  99. EP250225a: TRT optical upper limits
  100. EP250226a/GRB 250226A: 1.6m Mephisto observations

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