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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. EP250225a: Global MASTER-Net observations report
  2. EP250225a: GSP optical upper limit
  3. EP250223a: GMG Optical Observation
  4. EP250225a: Einstein Probe detected of a fast X-ray transient
  5. EP250223a: GROWTH-India Telescope optical observations
  6. EP250215A: J band upper limit by SYSU 80cm telescope
  7. EP250223a: Kinder optical follow-up observations
  8. GRB 250219A: EP-FXT afterglow detection
  9. EP250223a: GOTO optical afterglow detections
  10. EP250223a: TRT optical afterglow observation
  11. EP250223a: refined analysis of the EP-WXT and FXT observations
  12. EP250223a: 1.6m Mephisto and 50cm array observations
  13. EP250223a: SVOM/VT optical observation
  14. The EP-WXT trigger 01709131882 is likely a flaring star
  15. EP250223a: OASDG optical observations
  16. EP250223a: LCO detection of the afterglow
  17. EP250223a: early optical detection by BOOTES-4
  18. EP250223a: NOT redshift z = 2.756
  19. EP250223a: Swift/XRT localization
  20. EP250223a: NOT optical afterglow candidate
  21. EP250223a: Global MASTER-Net observations report
  22. EP250223a: Einstein Probe detection of an X-ray transient
  23. Konus-Wind detection of GRB 250221A
  24. EP250220a: FTW optical and NIR observations and upper limits
  25. EP250220a: EP-FXT follow-up observations
  26. EP250220a: Liverpool Telescope upper limits
  27. EP250220a: 1.6m Mephisto observations
  28. EP250220a: Liverpool Telescope optical upper limits
  29. EP250220a: Optical upper limit with Kinder observations
  30. EP250220a: Xinglong optical upper limit
  31. EP250220a: Global MASTER-Net observations report
  32. EP250220a: EP-WXT detection of a fast X-ray transient
  33. Konus-Wind detection of GRB 250217C (short)
  34. Konus-Wind detection of GRB 250215A / EP250215a
  35. The EP-WXT trigger 01709131775 is likely a flaring star
  36. GRB 250215A / EP250215a: LCO detection of the afterglow
  37. EP250212a: FTW optical and NIR upper limits
  38. EP250215a / GRB 250215A : GTC redshift z = 4.61
  39. GRB 250215A: Fermi GBM Observation
  40. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  41. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  42. GRB 250215A: Swift-XRT refined Analysis
  43. GRB 250215A: SVOM/GRM observation
  44. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  45. EP250215a: Global MASTER-Net observations report
  46. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  47. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  48. EP250207b: Xinglong optical upper limit
  49. EP250212a: Xinglong optical upper limit
  50. EP250212a: Global MASTER-Net observations report
  51. EP250207B: Chandra localization of the X-ray counterpart
  52. EP250207b: VLA radio upper limits
  53. EP250212a: Liverpool Telescope optical upper limits
  54. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  55. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  56. EP250207B: GTC z-band Observations
  57. EP250207b: NOT optical counterpart candidate
  58. Konus-Wind detection of GRB 250207A
  59. Konus-Wind detection of GRB 250206A
  60. EP250207b: Liverpool Telescope possible optical counterpart
  61. EP250207b: Global MASTER-Net observations report
  62. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  63. EP250207b: Gemini GMOS-N z-band observations
  64. EP250207A: Upper limits from Fermi-GBM Observations
  65. EP250207b: a new X-ray transient detected by Einstein Probe
  66. EP250207a: EP-WXT detection and XRT follow-up observation
  67. EP-WXT trigger 01709131361: correction to GCN 39214
  68. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  69. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  70. Konus-Wind detection of GRB 250204B
  71. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  72. The EP-WXT trigger 01709131347 is likely a flaring star
  73. The EP-WXT trigger 01709131332 is likely a flaring star
  74. The EP-WXT trigger 01709131290 is likely a flaring star
  75. EP250205a/GRB 250205A: correction to the source localization
  76. EP250205a/GRB 250205A: Einstein Probe observation
  77. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  78. GRB 250205A: GOTO optical upper limits
  79. Konus-Wind detection of GRB 250201A
  80. Konus-Wind detection of GRB 250202B
  81. EP 250108A: Upper limits from Fermi-GBM Observations
  82. The EP-WXT trigger 01709131196 is likely a flaring star
  83. The EP-WXT trigger 01709131153 is not a real source
  84. Konus-Wind detection of GRB 250129A
  85. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  86. Ep250125A: 1.3m DFOT optical upper limit
  87. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  88. GRB 250127A: CrAO and Terskol optical upper limits
  89. The EP-WXT trigger 01709131085 is likely a flaring star
  90. EP250125a: Upper limits from Swift/BAT-GUANO
  91. GRB 250127A: Swift-XRT observations
  92. GRB 250127A: EP-FXT afterglow detection
  93. EP250125A: Non-detection from Fermi-GBM Observations
  94. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  95. EP250125a: Optical upper limit with Kinder observations
  96. EP250125a: REM optical counterpart detection
  97. EP250125a: Swift/XRT detection of a fading counterpart
  98. EP250125a: a new X-ray transient detected by Einstein Probe
  99. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  100. The EP-WXT trigger 01709130758 is a false trigger

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