Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
  1. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  2. Fermi GRB 240504A: Global MASTER-Net observations report
  3. Fermi trigger No 736472503: Global MASTER-Net observations report
  4. GW170817: VLA observations at ~5.5 yrs since merger
  5. GRB 240503A: AstroSat CZTI detection
  6. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  7. GRB 240504A: Fermi GBM Final Real-time Localization
  8. Fermi trigger No 736387941: Global MASTER-Net observations report
  9. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  10. GRB 240502A: GOTO optical upper limit
  11. Fermi trigger No 736379109: Global MASTER-Net observations report
  12. GRB 240502A: Fermi GBM Observation
  13. GRB 240415A 1.3m DFOT Optical upper limit
  14. GRB 240502C: GOTO possible optical counterpart candidates
  15. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  16. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  17. Fermi GRB 240502B: Global MASTER-Net observations report
  18. GRB 240502C: Fermi GBM Final Localization
  19. Fermi GRB 240502A: Global MASTER-Net observations report
  20. GRB 240501B: GRBAlpha detection
  21. GRB 240430A: GRBAlpha detection
  22. GRB 240502B: Fermi GBM Final Real-time Localization
  23. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  24. Integral GRB240502.23: Global MASTER-Net observations report
  25. GRB 240502A long GRB detected by INTEGRAL
  26. GRB 240502A: Fermi GBM Final Real-time Localization
  27. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  28. Fermi GRB 240501A: Global MASTER-Net observations report
  29. Fermi trigger No 736197684: Global MASTER-Net observations report
  30. GRB 240426A: VZLUSAT-2 detection
  31. GRB 240425A: VZLUSAT-2 detection
  32. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  33. GRB240430A: Fermi GBM Final Localization
  34. GRB 240501B: AstroSat CZTI detection
  35. GRB 240501A: Fermi GBM Final Real-time Localization
  36. GRB 240408B: VZLUSAT-2 detection
  37. GRB 240407A: VZLUSAT-2 detection
  38. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  39. X-ray transient EP240414a: Detection of associated supernova
  40. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  41. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  42. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  43. Additional DECam GW-MMADS Candidates from three nights of observations
  44. GRB 240425A: GRBAlpha detection
  45. Fermi-LAT gamma-ray observations of IceCube-240424A
  46. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  47. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  48. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  49. GRB 240429A: Fermi GBM Final Real-time Localization
  50. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  51. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  52. LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  54. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  55. Fermi GRB 240428A: Global MASTER-Net observations report
  56. GRB 240428A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  58. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  59. EP240426b: AST3-2 optical upper limit
  60. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  61. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  62. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  63. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  64. EP240426b: EP-WXT detection of a new fast X-ray transient
  65. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  66. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  67. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  68. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  69. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  70. GRB 240426A: AstroSat CZTI detection
  71. EP240426a: YAHPT optical upper limit
  72. XMM-Newton observation of EP240426a
  73. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  75. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  76. GRB 240414A: NOEMA detection
  77. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  78. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  79. EP240426a: GMG optical upper limit
  80. LVK S240422ed: Further Swift-XRT followup of three sources
  81. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  82. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  83. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  84. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  85. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  86. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  87. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  88. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  89. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  90. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  91. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  92. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  93. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  94. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  95. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  96. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  97. LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
  98. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  99. GRB 240425A: Fermi GBM Final Real-time Localization
  100. Fermi trigger No 735697285: 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