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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').

18174 results found.

  1. GRB 250314A: NOT near-infrared candidate counterpart
  2. GRB 250312B: Fermi GBM Observation
  3. GRB 250313A: Swift-XRT observations
  4. Konus-Wind detection of GRB 250308A
  5. GRB 250313A: Fermi-LAT detection
  6. GRB 250313A: Swift ToO observations
  7. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  8. EP250304a: SVOM/VT optical observation
  9. EP250302a: Chandra X-ray Detection
  10. GRB 250312A: Swift-XRT refined Analysis
  11. GRB 250312A: Enhanced Swift-XRT position
  12. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  13. GRB 250226B: Fermi GBM Observation
  14. Swift GRB 250312A: Global MASTER-Net observations report
  15. GRB 250302A: Fermi GBM Observation
  16. GRB 250312A: Swift detection of a burst
  17. GRB 250223B: Fermi GBM Observation
  18. GRB 250311A: Swift-XRT observations
  19. GRB 250228A: Fermi GBM Observation
  20. GRB 230509B: 1.3m DFOT Optical observations
  21. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  22. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  24. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  25. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  26. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  27. EP250304a: Chandra detection
  28. GRB 250225B: Swift-BAT refined analysis
  29. GRB 250311A: Tiled Swift observations
  30. IPN triangulation of GRB 250308A (short)
  31. GRB 250309B: Swift-XRT refined Analysis
  32. GRB 250309B / AT2025dws: Swift-UVOT detection
  33. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  34. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  35. GRB 230509B: Tiled Swift observations
  36. GRB 250306A: EIRSAT-1 GMOD detection
  37. Konus-Wind detection of GRB 250306A
  38. GRB 250306A: Swift-BAT refined analysis
  39. GRB 250306A: NuSTAR detection of the prompt emission
  40. GRB 250306A: AstroSat CZTI detection
  41. Swift GRB 250306A: Global MASTER-Net observations report
  42. GRB 250306A: Swift detection of a burst
  43. IPN triangulation of GRB 250222A
  44. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  45. EP250304a: Swift-XRT detection of a fading X-ray source
  46. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  47. EP250302a: Swift/UVOT detection
  48. EP250302a: Swift-XRT observations of a fading X-ray source
  49. EP250228a: Optical observations with Kinder and Swift/UVOT
  50. GRB 250225B: EIRSAT-1 GMOD Detection
  51. GRB 250225B: VLT/HAWKI near-infrared observations
  52. EP250228a: updates on the EP observations
  53. EP250228a: Swift/XRT localisation
  54. GRB 250225B: INTEGRAL SPI-ACS detection
  55. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  56. GRB 250225B: Fermi GBM Observation
  57. GRB 250221A: ATCA Detections and Upper Limits
  58. GRB 250225B: REM NIR upper limits
  59. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  60. Konus-Wind detection of GRB 250225B
  61. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  62. GRB 250225B: VLT/FORS2 candidate optical afterglow
  63. GRB 250225B: SVOM/GRM observation of a long burst
  64. GRB 250221A: EP-FXT detection of the X-ray afterglow
  65. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  66. Swift GRB 250225B: Global MASTER-Net observations report
  67. GRB 250225B: Swift detection of a burst
  68. GRB 250221A: Swift-BAT refined analysis
  69. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  70. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  71. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  72. GRB 250207a: ATCA Radio Upper Limits
  73. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  75. GRB 250119B: VZLUSAT-2 detection
  76. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  77. GRB 250219A: EP-FXT afterglow detection
  78. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  79. EP250223a: REM NIR upper limit
  80. EP250223a: TRT optical afterglow observation
  81. EP250223a: refined analysis of the EP-WXT and FXT observations
  82. EP250223a: SVOM/VT optical observation
  83. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  84. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  85. EP250223a: OASDG optical observations
  86. EP250223a: LCO detection of the afterglow
  87. EP250223a: early optical detection by BOOTES-4
  88. EP250223a: NOT redshift z = 2.756
  89. EP250223a: Swift/XRT localization
  90. GRB 250221A: VLA radio detection
  91. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  92. GRB 250221A: continued Mondy optical observations, brightening afterglow
  93. GRB 250221A: Optical counterpart detection by LCO.
  94. GRB 250221A: Mondy optical observations
  95. Konus-Wind detection of GRB 250221A
  96. GRB 250221A: Assy optical observations
  97. GRB 250221A: GRANDMA/TAROT Detection
  98. GRB 250221A: Swift-XRT refined Analysis
  99. GRB 250221A: NOT optical observations
  100. GRB 250221A: 1.6m Mephisto optical detection

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