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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"

2969 results found.

  1. EP250220a: EP-FXT follow-up observations
  2. EP250220a: Liverpool Telescope upper limits
  3. EP250220a: 1.6m Mephisto observations
  4. EP250220a: Liverpool Telescope optical upper limits
  5. EP250220a: Optical upper limit with Kinder observations
  6. EP250220a: Xinglong optical upper limit
  7. EP250220a: Global MASTER-Net observations report
  8. EP250220a: EP-WXT detection of a fast X-ray transient
  9. Konus-Wind detection of GRB 250217C (short)
  10. Konus-Wind detection of GRB 250215A / EP250215a
  11. The EP-WXT trigger 01709131775 is likely a flaring star
  12. GRB 250215A / EP250215a: LCO detection of the afterglow
  13. EP250212a: FTW optical and NIR upper limits
  14. EP250215a / GRB 250215A : GTC redshift z = 4.61
  15. GRB 250215A: Fermi GBM Observation
  16. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  17. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  18. GRB 250215A: Swift-XRT refined Analysis
  19. GRB 250215A: SVOM/GRM observation
  20. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  21. EP250215a: Global MASTER-Net observations report
  22. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  23. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  24. EP250207b: Xinglong optical upper limit
  25. EP250212a: Xinglong optical upper limit
  26. EP250212a: Global MASTER-Net observations report
  27. EP250207B: Chandra localization of the X-ray counterpart
  28. EP250207b: VLA radio upper limits
  29. EP250212a: Liverpool Telescope optical upper limits
  30. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  31. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  32. EP250207B: GTC z-band Observations
  33. EP250207b: NOT optical counterpart candidate
  34. Konus-Wind detection of GRB 250207A
  35. Konus-Wind detection of GRB 250206A
  36. EP250207b: Liverpool Telescope possible optical counterpart
  37. EP250207b: Global MASTER-Net observations report
  38. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  39. EP250207b: Gemini GMOS-N z-band observations
  40. EP250207A: Upper limits from Fermi-GBM Observations
  41. EP250207b: a new X-ray transient detected by Einstein Probe
  42. EP250207a: EP-WXT detection and XRT follow-up observation
  43. EP-WXT trigger 01709131361: correction to GCN 39214
  44. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  45. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  46. Konus-Wind detection of GRB 250204B
  47. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  48. The EP-WXT trigger 01709131347 is likely a flaring star
  49. The EP-WXT trigger 01709131332 is likely a flaring star
  50. The EP-WXT trigger 01709131290 is likely a flaring star
  51. EP250205a/GRB 250205A: correction to the source localization
  52. EP250205a/GRB 250205A: Einstein Probe observation
  53. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  54. GRB 250205A: GOTO optical upper limits
  55. Konus-Wind detection of GRB 250201A
  56. Konus-Wind detection of GRB 250202B
  57. EP 250108A: Upper limits from Fermi-GBM Observations
  58. The EP-WXT trigger 01709131196 is likely a flaring star
  59. The EP-WXT trigger 01709131153 is not a real source
  60. Konus-Wind detection of GRB 250129A
  61. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  62. Ep250125A: 1.3m DFOT optical upper limit
  63. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  64. GRB 250127A: CrAO and Terskol optical upper limits
  65. The EP-WXT trigger 01709131085 is likely a flaring star
  66. EP250125a: Upper limits from Swift/BAT-GUANO
  67. GRB 250127A: Swift-XRT observations
  68. GRB 250127A: EP-FXT afterglow detection
  69. EP250125A: Non-detection from Fermi-GBM Observations
  70. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  71. EP250125a: Optical upper limit with Kinder observations
  72. EP250125a: REM optical counterpart detection
  73. EP250125a: Swift/XRT detection of a fading counterpart
  74. EP250125a: a new X-ray transient detected by Einstein Probe
  75. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  76. The EP-WXT trigger 01709130758 is a false trigger
  77. The EP-WXT trigger 01709130758 is a false trigger
  78. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  79. Konus-Wind detection of GRB 250118B
  80. Konus-Wind detection of GRB 250119B
  81. Konus-Wind detection of GRB 250117A
  82. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  83. EP 250108A: Late-time optical observation by LCO
  84. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  85. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  86. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  87. EP250108a / AT2025kg: GMG Optical Observations
  88. Konus-Wind detection of GRB 250116A
  89. Konus-Wind detection of GRB 250113A
  90. EP250111a: SAO RAS optical upper limit
  91. EP250108a / AT 2025kg: SAO RAS optical observations
  92. EP241021a: SMA radio observation
  93. EP250109b: optical upper limits with the Liverpool Telescope
  94. GRB 250109A / EP250109a: GRBAlpha detection
  95. GRB 250109A / EP250109a: Mephisto optical upper limits
  96. EP250108a: Mephisto detection
  97. EP250108a / AT 2025kg: LCO optical observations
  98. EP250111a: Global MASTER-Net observations report
  99. EP250111a: Swift/XRT detection and fading
  100. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification

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