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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. EP250304a: Swift-XRT detection of a fading X-ray source
  2. EP250304a: TRT optical counterpart detection
  3. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  4. EP250304a: Global MASTER-Net observations report
  5. EP250304a: Einstein Probe detection of an X-ray transient
  6. The EP-WXT trigger 01709132212 is not a real source
  7. EP250302a: SVOM/VT optical observation
  8. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  9. EP250302a: SAO RAS optical observations
  10. EP250302a : GIT optical follow-up
  11. EP250302a: VLT/X-shooter redshift confirmation
  12. EP250225a: the candidate optical counterpart is an AGN
  13. EP250302a: Kinder optical follow-up observations
  14. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  15. EP250302a: Swift/UVOT detection
  16. EP250302a: NUTTelA-TAO Early Measurments
  17. EP250302a: optical observation from the INAF Asiago Observatory
  18. EP250302a: REM NIR upper limits
  19. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  20. EP250302a: Mondy Observations and Optical Light Curve
  21. EP250302a: VLT/MUSE optical redshift z = 1.131
  22. INTEGRAL: end of scientific operations
  23. EP250302A: VLT near-infrared observations
  24. EP250302A: VLT/X-shooter tentative redshift
  25. EP250302a: OHP/T193 optical and spectroscopic observations
  26. EP250302a: Global MASTER-Net observations report
  27. EP250302a: Xinglong F60B optical observation
  28. EP250302a: Swift-XRT observations of a fading X-ray source
  29. EP250302a: Einstein Probe detection of an X-ray transient
  30. EP250302a: SVOM/C-GFT optical observations
  31. GRB 250226A: GRANDMA Optical Observations
  32. EP250302a: Montarrenti Observatory optical detection
  33. Fermi GRB 250302A: Global MASTER-Net observations report
  34. EP250302a: FTW optical and NIR detection
  35. EP250302a: Nanshan/HMT optical counterpart detection
  36. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 250302A: Fermi GBM Final Real-time Localization
  38. GRB 250228A: Fermi GBM Final Localization
  39. The EP-WXT trigger 01709132140 is likely a flaring star
  40. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  41. GRB 250225B: VLT near-infrared afterglow confirmation
  42. EP250228a: Optical observations with Kinder and Swift/UVOT
  43. Konus-Wind detection of GRB 250226A
  44. GRB 250225B: EIRSAT-1 GMOD Detection
  45. GRB 250226A: KAO Optical Upper Limit
  46. GRB 250226A: AbAO AS-32 Optical Upper Limit
  47. EP250227a: Global MASTER-Net observations report
  48. EP250223A: Upper limits from Fermi-GBM Observations
  49. EP250227a: TRT optical upper limit
  50. GRB 250225B: VLT/HAWKI near-infrared observations
  51. EP250227a: Optical upper limits with Kinder observations
  52. EP250227a: NOT optical observations
  53. EP250227a: Einstein Probe detected of a fast X-ray transient
  54. EP250228a: updates on the EP observations
  55. GRB 250226A: Fermi GBM Observation
  56. EP250225a: EP-FXT follow-up observation
  57. EP250223a: J band upper limit by SYSU 80cm telescope
  58. EP250228a: Swift/XRT localisation
  59. EP250228a: Global MASTER-Net observations report
  60. EP250228a: Einstein Probe detection of an X-ray transient
  61. GRB 250226A / EP250226a: LCO detection of the afterglow
  62. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  63. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  64. GRB 250225B: VLT/Xshooter imaging
  65. GRB 250205A / EP250205A: further radio observations with the VLA
  66. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  67. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  68. GRB 250225B: INTEGRAL SPI-ACS detection
  69. EP250225a: NOT optical candidate counterpart
  70. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  71. EP250226a / GRB 250226A: SVOM/VT optical observations
  72. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  73. EP250225a: TRT optical upper limits
  74. EP250226a/GRB 250226A: 1.6m Mephisto observations
  75. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  76. EP250226a/GRB 250226A: Kinder optical follow-up observations
  77. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  78. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  79. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  80. Fermi GRB 250226B: Global MASTER-Net observations report
  81. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  82. GRB 250226B: Fermi GBM Final Real-time Localization
  83. GRB 250225B: Fermi GBM Observation
  84. GRB 250221A: ATCA Detections and Upper Limits
  85. GRB 250225B: REM NIR upper limits
  86. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  87. Konus-Wind detection of GRB 250225B
  88. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  89. EP250223a: CrAO ZTSH optical observation
  90. GRB 250225B: VLT optical and near-infrared candidate counterpart
  91. GRB 250225B: VLT/FORS2 candidate optical afterglow
  92. GRB 250225B: SVOM/GRM observation of a long burst
  93. GRB 250226A: GECAM-B detection
  94. GRB 250221A: EP-FXT detection of the X-ray afterglow
  95. GRB 250214A: SVOM/GRM observation
  96. EP250226a/GRB 250226A: GSP detects optical counterpart
  97. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  98. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  99. EP250226a / GRB 250226A: TRT optical counterpart observation
  100. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources

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