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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"

32509 results found.

  1. Fermi GRB 250307A: Global MASTER-Net observations report
  2. Konus-Wind detection of GRB 250306A
  3. GRB 250306A: Swift-BAT refined analysis
  4. GRB 250306A: NuSTAR detection of the prompt emission
  5. EP250304a: MeerKAT detection of a possible radio counterpart
  6. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  7. GRB 250305A: AstroSat CZTI detection
  8. EP250302a:Xinglong optical observations
  9. GRB 250306A: AstroSat CZTI detection
  10. Swift GRB 250306A: Global MASTER-Net observations report
  11. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  12. GRB250101A: Radio upper limits from VLA observations
  13. GRB 250305A: SVOM/GRM observation of a burst
  14. EP250304A: Upper limits from Fermi-GBM Observations
  15. Fermi GRB 250305A: Global MASTER-Net observations report
  16. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  17. EP250302a: Optical Observations at CrAO and SAO RAS
  18. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  19. EP 250304A: Optical counterpart detection by LCO
  20. EP250302A: 1.3m DFOT optical afterglow detection
  21. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  22. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  23. Konus-Wind detection of GRB 250222A
  24. EP250304a: REM NIR upper limits
  25. IPN triangulation of GRB 250222A
  26. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  27. EP250302a: Mondy Continued Optical Observations
  28. EP250304a: VLT/X-shooter redshift z = 0.200
  29. EP250304a: Swift-XRT detection of a fading X-ray source
  30. EP250304a: TRT optical counterpart detection
  31. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  32. EP250304a: Global MASTER-Net observations report
  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. EP250302a: Swift/UVOT detection
  41. EP250302a: NUTTelA-TAO Early Measurments
  42. EP250302a: optical observation from the INAF Asiago Observatory
  43. EP250302a: REM NIR upper limits
  44. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  45. EP250302a: Mondy Observations and Optical Light Curve
  46. EP250302a: VLT/MUSE optical redshift z = 1.131
  47. INTEGRAL: end of scientific operations
  48. EP250302A: VLT near-infrared observations
  49. EP250302A: VLT/X-shooter tentative redshift
  50. EP250302a: OHP/T193 optical and spectroscopic observations
  51. EP250302a: Global MASTER-Net observations report
  52. EP250302a: Xinglong F60B optical observation
  53. EP250302a: Swift-XRT observations of a fading X-ray source
  54. EP250302a: Einstein Probe detection of an X-ray transient
  55. EP250302a: SVOM/C-GFT optical observations
  56. GRB 250226A: GRANDMA Optical Observations
  57. EP250302a: Montarrenti Observatory optical detection
  58. Fermi GRB 250302A: Global MASTER-Net observations report
  59. EP250302a: FTW optical and NIR detection
  60. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  61. GRB 250225B: VLT near-infrared afterglow confirmation
  62. EP250228a: Optical observations with Kinder and Swift/UVOT
  63. Konus-Wind detection of GRB 250226A
  64. GRB 250225B: EIRSAT-1 GMOD Detection
  65. GRB 250226A: KAO Optical Upper Limit
  66. GRB 250226A: AbAO AS-32 Optical Upper Limit
  67. EP250227a: Global MASTER-Net observations report
  68. EP250223A: Upper limits from Fermi-GBM Observations
  69. EP250227a: TRT optical upper limit
  70. GRB 250225B: VLT/HAWKI near-infrared observations
  71. EP250227a: Optical upper limits with Kinder observations
  72. EP250227a: NOT optical observations
  73. EP250228a: updates on the EP observations
  74. GRB 250226A: Fermi GBM Observation
  75. EP250225a: EP-FXT follow-up observation
  76. EP250223a: J band upper limit by SYSU 80cm telescope
  77. EP250228a: Swift/XRT localisation
  78. EP250228a: Global MASTER-Net observations report
  79. GRB 250226A / EP250226a: LCO detection of the afterglow
  80. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  81. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  82. GRB 250225B: VLT/Xshooter imaging
  83. GRB 250205A / EP250205A: further radio observations with the VLA
  84. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  85. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  86. GRB 250225B: INTEGRAL SPI-ACS detection
  87. EP250225a: NOT optical candidate counterpart
  88. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  89. EP250226a / GRB 250226A: SVOM/VT optical observations
  90. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  91. EP250225a: TRT optical upper limits
  92. EP250226a/GRB 250226A: 1.6m Mephisto observations
  93. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  94. EP250226a/GRB 250226A: Kinder optical follow-up observations
  95. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  96. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  97. Fermi GRB 250226B: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  99. GRB 250225B: Fermi GBM Observation
  100. GRB 250221A: ATCA Detections and Upper Limits

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