Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

20815 results found.

  1. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  2. GRB 250312A: Swift detection of a burst
  3. GRB 241213A: VIRT Optical Upper Limit
  4. GRB 241228A: VIRT Optical Upper Limit
  5. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  6. GRB 250311A: Swift-XRT observations
  7. GRB 230509B: 1.3m DFOT Optical observations
  8. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  9. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  10. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  11. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  12. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  13. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  14. GRB 250309B: PRIME near-infrared detection
  15. GRB 250225B: Swift-BAT refined analysis
  16. GRB 250311A/EP250311a: TRT optical upper limit
  17. EP250311a/GRB 250311A: EP-WXT detection
  18. GRB 250309B / AT2025dws: further SAO RAS optical observations
  19. IceCube-250309A: Upper limits from Fermi-GBM Observations
  20. EP250308a: 1.6m Mephisto optical upper limits
  21. IPN triangulation of GRB 250308A (short)
  22. IPN triangulation of GRB 250309B
  23. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  24. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  25. GRB 250309B / IceCube-250309A: GECAM-B observations
  26. GRB 250309B / AT2025dws: SAO RAS optical observations
  27. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  28. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  29. IceCube-250309A: No candidates from the Zwicky Transient Facility
  30. EP250308a: FTW optical and NIR upper limits
  31. EP250308a: Einstein Probe detection of an X-ray transient
  32. EP250308a: NOT optical upper limit
  33. Konus-Wind detection of GRB 250306A
  34. EP250304a: MeerKAT detection of a possible radio counterpart
  35. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  36. EP250302a:Xinglong optical observations
  37. GRB 250306A: AstroSat CZTI detection
  38. GRB 250306A: Swift detection of a burst
  39. GRB250101A: Radio upper limits from VLA observations
  40. GRB 250305A: SVOM/GRM observation of a burst
  41. EP250302a: Optical Observations at CrAO and SAO RAS
  42. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  43. EP 250304A: Optical counterpart detection by LCO
  44. EP250302A: 1.3m DFOT optical afterglow detection
  45. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  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: Swift-XRT detection of a fading X-ray source
  51. EP250304a: TRT optical counterpart detection
  52. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  53. EP250304a: Einstein Probe detection of an X-ray transient
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  55. EP250302a: SAO RAS optical observations
  56. EP250302a : GIT optical follow-up
  57. EP250302a: Kinder optical follow-up observations
  58. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  59. EP250302a: Swift/UVOT detection
  60. EP250302a: optical observation from the INAF Asiago Observatory
  61. EP250302a: REM NIR upper limits
  62. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  63. EP250302a: Mondy Observations and Optical Light Curve
  64. EP250302a: VLT/MUSE optical redshift z = 1.131
  65. EP250302A: VLT near-infrared observations
  66. EP250302A: VLT/X-shooter tentative redshift
  67. EP250302a: OHP/T193 optical and spectroscopic observations
  68. EP250302a: Einstein Probe detection of an X-ray transient
  69. EP250302a: SVOM/C-GFT optical observations
  70. GRB 250226A: GRANDMA Optical Observations
  71. EP250302a: Montarrenti Observatory optical detection
  72. EP250302a: Nanshan/HMT optical counterpart detection
  73. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  74. GRB 250225B: VLT near-infrared afterglow confirmation
  75. EP250228a: Optical observations with Kinder and Swift/UVOT
  76. GRB 250226A: KAO Optical Upper Limit
  77. GRB 250226A: AbAO AS-32 Optical Upper Limit
  78. EP250227a: TRT optical upper limit
  79. GRB 250225B: VLT/HAWKI near-infrared observations
  80. EP250227a: Optical upper limits with Kinder observations
  81. EP250227a: NOT optical observations
  82. EP250227a: Einstein Probe detected of a fast X-ray transient
  83. EP250228a: updates on the EP observations
  84. EP250225a: EP-FXT follow-up observation
  85. EP250223a: J band upper limit by SYSU 80cm telescope
  86. EP250228a: Einstein Probe detection of an X-ray transient
  87. GRB 250225B: VLT/Xshooter imaging
  88. GRB 250205A / EP250205A: further radio observations with the VLA
  89. GRB 250225B: INTEGRAL SPI-ACS detection
  90. EP250225a: NOT optical candidate counterpart
  91. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  92. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  93. EP250225a: TRT optical upper limits
  94. EP250226a/GRB 250226A: 1.6m Mephisto observations
  95. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  96. EP250226a/GRB 250226A: Kinder optical follow-up observations
  97. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  99. GRB 250221A: ATCA Detections and Upper Limits
  100. GRB 250225B: REM NIR upper limits

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