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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"

8293 results found.

  1. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP250402a: Optical upper limit with Kinder observations
  3. GRB 250403A: LCO optical counterpart detection
  4. GRB 250403A: GOTO detection of the optical afterglow
  5. GRB 250402A: REM optical/NIR upper limits
  6. GRB 250402A: refined SVOM/MXT data analysis
  7. GRB 250219A: NOT candidate host galaxy detection
  8. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  9. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  10. GRB 250331D: Swift ToO observations
  11. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  12. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  13. GRB 250328A: Swift-XRT refined Analysis
  14. GRB 250331C: Swift detection of a burst
  15. GRB 250331B: Swift detection of a burst
  16. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  17. GRB 250328A: 1.6m Mephisto optical observations
  18. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  20. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  21. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  22. GRB 250329A: Swift-XRT afterglow detection
  23. GRB 250328A: SVOM/VT optical observation
  24. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  25. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  26. GRB 250329A: VLT/X-shooter redshift z = 2.921
  27. GRB 250329A: SVOM/VT optical counterpart confirmation
  28. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  29. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  30. EP250315a: Pan-STARRS r and i-band imaging and photometry
  31. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  32. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  33. GRB 250327B: 1.6m Mephisto optical observations
  34. GRB 250327B: SVOM/VT optically bright counterpart
  35. GRB 250327B: SAO RAS optical candidate
  36. GRB 250327A: SVOM/VT optical candidate
  37. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  38. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  39. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  40. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  41. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  42. GRB 250322A: further NOT optical observations
  43. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  44. GRB 250322A: Gemini-North redshift of candidate host galaxy
  45. GRB 250322A: VLT optical observations
  46. GRB 250322A: VLT near-infrared observations
  47. GRB 250322A: NOT optical upper limits
  48. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  49. GRB 250322A: Swift detection of a short burst
  50. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  51. GRB 250321B: Swift ToO observations
  52. GRB 250321B: SVOM detection of a sub-threshold transient event
  53. EP250321a: Kinder optical follow-up observations
  54. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  55. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  56. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  57. GRB 250309B/AT2025dws: further ATCA observations
  58. GRB 250316A: AbAO AS-32 Optical Upper Limit
  59. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  60. GRB 250316A: Swift ToO observations
  61. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  62. GRB 250314A: EP-FXT afterglow detection
  63. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP250315a: optical counterpart candidate detected by Gemini North
  65. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  66. GRB 250314A: SVOM/VT upper limit
  67. GRB 250314A: NOT near-infrared candidate counterpart
  68. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  69. GRB 250313A: Swift ToO observations
  70. EP250304a: Pan-STARRS r and i-band imaging and photometry
  71. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  72. GRB 250312A: Swift detection of a burst
  73. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  74. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 250311A: Tiled Swift observations
  76. GRB 250309B: SVOM/VT optical observation
  77. GRB 250309B / AT2025dws: further SAO RAS optical observations
  78. IceCube-250309A: Upper limits from Fermi-GBM Observations
  79. Konus-Wind detection of GRB 250309B
  80. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  81. GRB 250309B / IceCube-250309A: GECAM-B observations
  82. GRB 250309B / AT2025dws: Swift-UVOT detection
  83. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  84. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  85. IceCube-250309A: No candidates from the Zwicky Transient Facility
  86. GRB 230509B: Tiled Swift observations
  87. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  88. The EP-WXT trigger 01709132387 is likely a flaring star
  89. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  90. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  91. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  92. EP250304A: Upper limits from Fermi-GBM Observations
  93. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  94. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  95. EP250225a: the candidate optical counterpart is an AGN
  96. EP250302a: Kinder optical follow-up observations
  97. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  98. EP250302a: Montarrenti Observatory optical detection
  99. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 250225B: VLT near-infrared afterglow confirmation

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