Skip to main content
End of INTEGRAL Operations. See news and announcements

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').

18148 results found.

  1. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  2. GRB 230509B: Tiled Swift observations
  3. GRB 250306A: EIRSAT-1 GMOD detection
  4. Konus-Wind detection of GRB 250306A
  5. GRB 250306A: Swift-BAT refined analysis
  6. GRB 250306A: NuSTAR detection of the prompt emission
  7. GRB 250306A: AstroSat CZTI detection
  8. Swift GRB 250306A: Global MASTER-Net observations report
  9. GRB 250306A: Swift detection of a burst
  10. IPN triangulation of GRB 250222A
  11. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  12. EP250304a: Swift-XRT detection of a fading X-ray source
  13. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  14. EP250302a: Swift/UVOT detection
  15. EP250302a: Swift-XRT observations of a fading X-ray source
  16. EP250228a: Optical observations with Kinder and Swift/UVOT
  17. GRB 250225B: EIRSAT-1 GMOD Detection
  18. GRB 250225B: VLT/HAWKI near-infrared observations
  19. EP250228a: updates on the EP observations
  20. EP250228a: Swift/XRT localisation
  21. GRB 250225B: INTEGRAL SPI-ACS detection
  22. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  23. GRB 250225B: Fermi GBM Observation
  24. GRB 250221A: ATCA Detections and Upper Limits
  25. GRB 250225B: REM NIR upper limits
  26. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  27. Konus-Wind detection of GRB 250225B
  28. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  29. GRB 250225B: VLT/FORS2 candidate optical afterglow
  30. GRB 250225B: SVOM/GRM observation of a long burst
  31. GRB 250221A: EP-FXT detection of the X-ray afterglow
  32. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  33. Swift GRB 250225B: Global MASTER-Net observations report
  34. GRB 250225B: Swift detection of a burst
  35. GRB 250221A: Swift-BAT refined analysis
  36. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  37. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  38. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  39. GRB 250207a: ATCA Radio Upper Limits
  40. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  41. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  42. GRB 250119B: VZLUSAT-2 detection
  43. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  44. GRB 250219A: EP-FXT afterglow detection
  45. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  46. EP250223a: REM NIR upper limit
  47. EP250223a: TRT optical afterglow observation
  48. EP250223a: refined analysis of the EP-WXT and FXT observations
  49. EP250223a: SVOM/VT optical observation
  50. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  51. 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
  52. EP250223a: OASDG optical observations
  53. EP250223a: LCO detection of the afterglow
  54. EP250223a: early optical detection by BOOTES-4
  55. EP250223a: NOT redshift z = 2.756
  56. EP250223a: Swift/XRT localization
  57. GRB 250221A: VLA radio detection
  58. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  59. GRB 250221A: continued Mondy optical observations, brightening afterglow
  60. GRB 250221A: Optical counterpart detection by LCO.
  61. GRB 250221A: Mondy optical observations
  62. Konus-Wind detection of GRB 250221A
  63. GRB 250221A: Assy optical observations
  64. GRB 250221A: GRANDMA/TAROT Detection
  65. GRB 250221A: Swift-XRT refined Analysis
  66. GRB 250221A: NOT optical observations
  67. GRB 250221A: 1.6m Mephisto optical detection
  68. GRB 250221A: AKO Optical Upper Limit
  69. GRB 250221A: Swift/UVOT Detection
  70. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  71. GRB 250221A: REM optical/NIR afterglow detection
  72. GRB 250221A: Enhanced Swift-XRT position
  73. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  74. GRB 250221A: Swift detection of a burst with an optical counterpart
  75. Swift GRB250221.15: Global MASTER-Net OT detection
  76. Swift GRB250221.15: Global MASTER-Net observations report
  77. GRB 250219A: Swift/UVOT Upper Limits
  78. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  79. GRB 250219A: 1.6m Mephisto optical upper limits
  80. GRB 250219A: SVOM/VT optical counterpart
  81. GRB 250219A: Swift-XRT observations
  82. GRB 250219A: Swift ToO observations
  83. GRB 250217C: Swift-XRT observations
  84. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  85. GRB 250217C: Tiled Swift observations
  86. IPN triangulation of GRB 250217C (short)
  87. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  88. SVOM/sb25021804: SVOM detection of a long X-ray transient
  89. GRB 250213A: Swift-XRT observations
  90. GRB 250215A / EP250215a: LCO detection of the afterglow
  91. GRB 250215A: Swift/UVOT Upper Limits
  92. GRB 250215A: Fermi GBM Observation
  93. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  94. GRB 250215A: Swift-XRT refined Analysis
  95. GRB 250213A: Swift ToO observations
  96. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  97. GRB 250211A: Swift ToO observations
  98. GRB 250207A: Fermi GBM Observation
  99. Konus-Wind detection of GRB 250207A
  100. GRB 250207A: Skynet optical afterglow observations

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov