Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

32532 results found.

  1. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  2. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  3. GRB 250309B: Swift-XRT refined Analysis
  4. GRB 250309B / IceCube-250309A: GECAM-B observations
  5. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  6. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  7. GRB 250309B / AT2025dws: SAO RAS optical observations
  8. GRB 250309B / AT2025dws: Swift-UVOT detection
  9. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  10. GRB 250309B: Fermi GBM Observation
  11. Fermi GRB 250309B: Global MASTER-Net observations report
  12. Fermi GRB 250309A: Global MASTER-Net observations report
  13. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  14. IceCube-250309A: No candidates from the Zwicky Transient Facility
  15. Fermi-LAT gamma-ray observations of IceCube-250309A
  16. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  17. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  18. GRB 230509B: Tiled Swift observations
  19. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  20. EP250308a: Global MASTER-Net observations report
  21. EP250308a: GSP optical upper limit
  22. GRB 250306A: EIRSAT-1 GMOD detection
  23. Fermi GRB 250307A: Global MASTER-Net observations report
  24. Konus-Wind detection of GRB 250306A
  25. GRB 250306A: Swift-BAT refined analysis
  26. GRB 250306A: NuSTAR detection of the prompt emission
  27. EP250304a: MeerKAT detection of a possible radio counterpart
  28. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  29. GRB 250305A: AstroSat CZTI detection
  30. EP250302a:Xinglong optical observations
  31. GRB 250306A: AstroSat CZTI detection
  32. Swift GRB 250306A: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  34. GRB250101A: Radio upper limits from VLA observations
  35. GRB 250305A: SVOM/GRM observation of a burst
  36. EP250304A: Upper limits from Fermi-GBM Observations
  37. Fermi GRB 250305A: Global MASTER-Net observations report
  38. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  39. EP250302a: Optical Observations at CrAO and SAO RAS
  40. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  41. EP 250304A: Optical counterpart detection by LCO
  42. EP250302A: 1.3m DFOT optical afterglow detection
  43. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  44. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  45. Konus-Wind detection of GRB 250222A
  46. EP250304a: REM NIR upper limits
  47. IPN triangulation of GRB 250222A
  48. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  49. EP250302a: Mondy Continued Optical Observations
  50. EP250304a: VLT/X-shooter redshift z = 0.200
  51. EP250304a: Swift-XRT detection of a fading X-ray source
  52. EP250304a: TRT optical counterpart detection
  53. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  54. EP250304a: Global MASTER-Net observations report
  55. EP250302a: SVOM/VT optical observation
  56. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  57. EP250302a: SAO RAS optical observations
  58. EP250302a : GIT optical follow-up
  59. EP250302a: VLT/X-shooter redshift confirmation
  60. EP250225a: the candidate optical counterpart is an AGN
  61. EP250302a: Kinder optical follow-up observations
  62. EP250302a: Swift/UVOT detection
  63. EP250302a: NUTTelA-TAO Early Measurments
  64. EP250302a: optical observation from the INAF Asiago Observatory
  65. EP250302a: REM NIR upper limits
  66. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  67. EP250302a: Mondy Observations and Optical Light Curve
  68. EP250302a: VLT/MUSE optical redshift z = 1.131
  69. INTEGRAL: end of scientific operations
  70. EP250302A: VLT near-infrared observations
  71. EP250302A: VLT/X-shooter tentative redshift
  72. EP250302a: OHP/T193 optical and spectroscopic observations
  73. EP250302a: Global MASTER-Net observations report
  74. EP250302a: Xinglong F60B optical observation
  75. EP250302a: Swift-XRT observations of a fading X-ray source
  76. EP250302a: Einstein Probe detection of an X-ray transient
  77. EP250302a: SVOM/C-GFT optical observations
  78. GRB 250226A: GRANDMA Optical Observations
  79. EP250302a: Montarrenti Observatory optical detection
  80. Fermi GRB 250302A: Global MASTER-Net observations report
  81. EP250302a: FTW optical and NIR detection
  82. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  83. GRB 250225B: VLT near-infrared afterglow confirmation
  84. EP250228a: Optical observations with Kinder and Swift/UVOT
  85. Konus-Wind detection of GRB 250226A
  86. GRB 250225B: EIRSAT-1 GMOD Detection
  87. GRB 250226A: KAO Optical Upper Limit
  88. GRB 250226A: AbAO AS-32 Optical Upper Limit
  89. EP250227a: Global MASTER-Net observations report
  90. EP250223A: Upper limits from Fermi-GBM Observations
  91. EP250227a: TRT optical upper limit
  92. GRB 250225B: VLT/HAWKI near-infrared observations
  93. EP250227a: Optical upper limits with Kinder observations
  94. EP250227a: NOT optical observations
  95. EP250228a: updates on the EP observations
  96. GRB 250226A: Fermi GBM Observation
  97. EP250225a: EP-FXT follow-up observation
  98. EP250223a: J band upper limit by SYSU 80cm telescope
  99. EP250228a: Swift/XRT localisation
  100. EP250228a: Global MASTER-Net observations report

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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