Skip to main content
New! BOOM Notices and Schema v7.0.0. 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').
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"

35325 results found.

  1. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  2. GRB 250309B: Fermi GBM Observation
  3. Fermi GRB 250309B: Global MASTER-Net observations report
  4. Fermi GRB 250309A: Global MASTER-Net observations report
  5. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  6. Fermi-LAT gamma-ray observations of IceCube-250309A
  7. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  8. GRB 250309B: Fermi GBM Final Localization
  9. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  10. GRB 230509B: Tiled Swift observations
  11. GRB 250308A: SVOM/GRM observation of a bright short burst
  12. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  14. GRB 250309A: Fermi GBM Final Real-time Localization
  15. GRB 250306A: EIRSAT-1 GMOD detection
  16. Fermi GRB 250307A: Global MASTER-Net observations report
  17. Konus-Wind detection of GRB 250306A
  18. GRB 250307A: Fermi GBM Final Real-time Localization
  19. GRB 250306A: Swift-BAT refined analysis
  20. GRB 250306A: NuSTAR detection of the prompt emission
  21. GRB 250305A: AstroSat CZTI detection
  22. GRB 250306A: AstroSat CZTI detection
  23. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  24. Swift GRB 250306A: Global MASTER-Net observations report
  25. GRB 250306A: Swift detection of a burst
  26. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  27. GRB 250305A: SVOM/GRM observation of a burst
  28. EP250304A: Upper limits from Fermi-GBM Observations
  29. Fermi GRB 250305A: Global MASTER-Net observations report
  30. GRB 250305A: Fermi GBM Final Real-time Localization
  31. EP250302a: Optical Observations at CrAO and SAO RAS
  32. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  33. EP 250304A: Optical counterpart detection by LCO
  34. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  35. Konus-Wind detection of GRB 250222A
  36. IPN triangulation of GRB 250222A
  37. EP250302a: Mondy Continued Optical Observations
  38. EP250304a: VLT/X-shooter redshift z = 0.200
  39. EP250302a: NUTTelA-TAO Early Measurments
  40. EP250302a: Mondy Observations and Optical Light Curve
  41. EP250302a: OHP/T193 optical and spectroscopic observations
  42. GRB 250226A: GRANDMA Optical Observations
  43. EP250302a: Montarrenti Observatory optical detection
  44. Fermi GRB 250302A: Global MASTER-Net observations report
  45. GRB 250302A: Fermi GBM Final Real-time Localization
  46. GRB 250228A: Fermi GBM Final Localization
  47. GRB 250225B: VLT near-infrared afterglow confirmation
  48. Konus-Wind detection of GRB 250226A
  49. GRB 250225B: EIRSAT-1 GMOD Detection
  50. GRB 250226A: KAO Optical Upper Limit
  51. GRB 250226A: AbAO AS-32 Optical Upper Limit
  52. EP250223A: Upper limits from Fermi-GBM Observations
  53. GRB 250225B: VLT/HAWKI near-infrared observations
  54. GRB 250226A: Fermi GBM Observation
  55. GRB 250226A / EP250226a: LCO detection of the afterglow
  56. GRB 250225B: VLT/Xshooter imaging
  57. GRB 250205A / EP250205A: further radio observations with the VLA
  58. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  59. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  60. GRB 250225B: INTEGRAL SPI-ACS detection
  61. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  62. EP250226a / GRB 250226A: SVOM/VT optical observations
  63. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  64. EP250226a/GRB 250226A: 1.6m Mephisto observations
  65. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  66. EP250226a/GRB 250226A: Kinder optical follow-up observations
  67. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  68. Fermi GRB 250226B: Global MASTER-Net observations report
  69. GRB 250226B: Fermi GBM Final Real-time Localization
  70. GRB 250225B: Fermi GBM Observation
  71. GRB 250221A: ATCA Detections and Upper Limits
  72. GRB 250225B: REM NIR upper limits
  73. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  74. Konus-Wind detection of GRB 250225B
  75. EP250223a: CrAO ZTSH optical observation
  76. GRB 250225B: VLT optical and near-infrared candidate counterpart
  77. GRB 250225B: VLT/FORS2 candidate optical afterglow
  78. GRB 250225B: SVOM/GRM observation of a long burst
  79. GRB 250226A: GECAM-B detection
  80. GRB 250221A: EP-FXT detection of the X-ray afterglow
  81. GRB 250214A: SVOM/GRM observation
  82. EP250226a/GRB 250226A: GSP detects optical counterpart
  83. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  84. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  85. EP250226a / GRB 250226A: TRT optical counterpart observation
  86. Swift GRB 250225B: Global MASTER-Net observations report
  87. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  88. Fermi GRB 250226A: Global MASTER-Net observations report
  89. GRB 250226A: Fermi GBM Final Real-time Localization
  90. Fermi GRB 250225A: Global MASTER-Net observations report
  91. GRB 250225B: Swift detection of a burst
  92. GRB 250221A: Swift-BAT refined analysis
  93. GRB 250223C: SVOM/GRM observation of a long burst
  94. GRB 250225A: Fermi GBM Final Real-time Localization
  95. GRB 250207a: ATCA Radio Upper Limits
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  97. GRB 250119B: VZLUSAT-2 detection
  98. GRB 250223C: Fermi GBM Final Real-time Localization
  99. GRB 250202B: VZLUSAT-2 detection
  100. GRB 250219A: EP-FXT afterglow detection

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