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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"

2993 results found.

  1. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  2. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  3. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  4. GRB 250506A: Xinglong 2.16m optical upper limit
  5. SVOM/sb25050601: EP-FXT observations
  6. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  7. GRB 250430A: NUTTelA-TAO Early Measurements
  8. SVOM/sb25043004: EP-FXT observations
  9. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  10. EP 250427A: Optical counterpart detection by LCO.
  11. EP250428b: FTW optical and NIR observations
  12. EP250428b: refined analysis of the EP-FXT follow-up observation
  13. EP250428b: SVOM/VT upper limit
  14. EP250428b: SAO RAS optical upper limit
  15. EP250428b: LAST optical upper limit
  16. EP250428b: Global MASTER-Net observations report
  17. EP250428b: Einstein Probe detection of a fast X-ray transient
  18. EP250427a: EP-FXT follow-up observations
  19. GRB250427A/EP250427a GIT optical afterglow detection:
  20. GRB 250427A: Swift-XRT refined Analysis
  21. EP250427a / GRB 250427A: LCO optical counterpart detection
  22. EP250427a: REM optical/NIR afterglow detection
  23. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  24. EP250427A: COLIBRÍ Optical Detection
  25. EP250427a: TRT optical counterpart detection
  26. EP 250427a: BOOTES-7 optical afterglow candidate
  27. EP250427a: Global MASTER-Net observations report
  28. EP250427a: Einstein Probe detection of a fast X-ray transient
  29. Konus-Wind detection of GRB 250424A
  30. GRB 250404A / EP250404a: GRBAlpha detection
  31. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  32. EP250421a: Upper limits from Fermi-GBM Observations
  33. EP250421a: NOT optical observations
  34. EP250421a: Swift/XRT counterpart detection
  35. EP250421a: Global MASTER-Net observations report
  36. EP250421a: Einstein Probe detection of an X-ray transient
  37. EP250421a: Mephisto optical counterpart confirmation
  38. EP250421a: JinShan likely optical counterpart
  39. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  40. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  41. GRB 250407A: rest-frame energetics from Konus-Wind observation
  42. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  43. EP250416a: Swift/XRT counterpart fading
  44. EP250416a: refined EP-WXT and EP-FXT analysis
  45. Konus-Wind detection of GRB 250403A
  46. EP20250416a: Swift/XRT counterpart detection
  47. EP250416a: Gemini South-GMOS optical counterpart
  48. EP250416a: GSP optical upper limit
  49. EP250416a: Global MASTER-Net observations report
  50. EP250416a: Einstein Probe detection of an X-ray transient
  51. EP250304a: ATCA radio observations
  52. GRB 250407A: Mondy and AbAO Optical Observations
  53. EP250227a: Further NOT optical observations
  54. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  55. EP250407a: Global MASTER-Net observations report
  56. GRB 250407A: LCO detection of a fading optical counterpart
  57. EP250407a: Swift-XRT observations
  58. Konus-Wind detection of GRB 250407A
  59. GRB 250407A: EP-WXT afterglow detection
  60. EP250407a: EP-WXT detection of a fast X-ray transient
  61. Konus-Wind detection of GRB 250406B (short/hard)
  62. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  63. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  64. Konus-Wind detection of GRB 250404A / EP250404a
  65. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  66. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  67. EP250402a: Optical upper limit with PD 1.3m observations
  68. GRB 250404A / EP250404a: NOT optical observations
  69. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  70. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  71. EP250404a: LCO optical counterpart detection
  72. EP250404a: Xinglong decaying optical counterpart
  73. EP250404a: Global MASTER-Net observations report
  74. EP250404a: AKO Optical Afterglow Detection
  75. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  76. EP250404a: Mephisto multi-band optical detection
  77. EP250321A: J band upper limit by SYSU 80cm telescope
  78. EP250404a: Nanshan/HMT optical counterpart detection
  79. EP250404a: Einstein Probe detection of an X-ray transient
  80. EP250402a: Optical upper limit with Kinder observations
  81. GRB 250402A: EP-FXT afterglow detection
  82. EP250402a: EP-FXT follow-up observations
  83. The EP-WXT trigger 01709133862 is a flaring star
  84. EP250402a: Einstein Probe detection of a fast X-ray transient
  85. Konus-Wind detection of GRB 250327B
  86. FRB 20250316A: FTW optical observations
  87. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  88. EP250315a: Pan-STARRS r and i-band imaging and photometry
  89. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  90. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  91. Konus-Wind detection of GRB 250322A (short)
  92. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  93. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  94. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  95. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  96. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  97. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  98. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  99. FRB 250316A: DDOTI Continued Optical Observations
  100. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060

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