Hubbry Logo
SN 1994DSN 1994DMain
Open search
SN 1994D
Community hub
SN 1994D
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
SN 1994D
SN 1994D
SN 1994D
View on Wikipedia
from Wikipedia
SN 1994D
A dusty spiral galaxy seen close to edge-on against a black background, with a bright point of white at lower left
Hubble Space Telescope image of SN 1994D, visible at lower left
Event typeSupernova
Type Ia[1]
Datec. 55.15 million years ago
(discovered 7 March 1994 by R. Treffers)[2]
InstrumentLeuschner Observatory
ConstellationVirgo
Right ascension12h 34m 02.395s[1]
Declination+07° 42′ 05.70″[1]
EpochB2000.0
Distance~55.15 million ly
Redshift0.0036, 0.0001, −0.0001, 0.0021, 0.0023, 0.0022, 0.0008, 0.0005, 0.0013, 0.0017, 0.0004, 0.0024, 0.0011, 0.0012, 0.0002
HostNGC 4526[2]
Progenitor typeWhite dwarf
Peak apparent magnitude+11.9[3]
Other designationsSN 1994D, AAVSO 1229+08
Preceded bySN 1994C[4]
Followed bySN 1994E[4]
  Related media on Commons
[edit on Wikidata]

SN 1994D was a Type Ia supernova event in the outskirts of galaxy NGC 4526, which was observed in 1994.

Observation

[edit]
Light curves in four photometric bands for SN 1994D, adapted from Richmond et al. (1995)[3]

It was offset by 9.0″ west and 7.8″ south of the galaxy center and positioned near a prominent dust lane.[1] It was caused by the explosion of a white dwarf star composed of carbon and oxygen.[5] This event was discovered on March 7, 1994 by R. R. Treffers and associates using the automated 30-inch telescope at Leuschner Observatory.[2] It reached peak visual brightness, magnitude 11.9, two weeks later on March 22.[5][3] Modelling of the light curve indicates the explosion would have been visible around March 3-4. A possible detection of helium in the spectrum was made by W. P. S. Meikle and associates in 1996.[1] A mass of 0.014 to 0.03 M☉ in helium would be needed to produce this feature.[6]

See also

[edit]

References

[edit]

Further reading

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

SN 1994D

View on Grokipedia
from Grokipedia
SN 1994D was a discovered on March 7, 1994, by astronomers R. R. Treffers, A. V. Filippenko, and S. D. Van Dyk using the Katzman Automatic Imaging Telescope at , located in the , a member of the approximately 16.4 Mpc from Earth. The explosion occurred between March 3 and 4, 1994 (Julian Date 2449414.5 to 2449415.5), and the supernova reached a peak apparent visual magnitude of 11.78 ± 0.02 around 12 days after discovery, corresponding to an of approximately −19.3 after corrections for decline rate and color. As a prototypical Type Ia event, SN 1994D exhibited a well-fitted by the delayed explosion model (M36), with multi-band UBVRI photometry showing a decline rate parameter Δm15(B) = 1.31 ± 0.08, aligning closely with standard Type Ia supernovae like SN 1992A and SN 1980N in nearby galaxies. Spectral observations revealed P-Cygni profiles indicative of (Si II) at expansion velocities of about 15,000 km/s near maximum light, along with a notable near- feature at ~1.0 μm attributed to neutral (He I), providing insights into the system's evolution and the thermonuclear explosion mechanism. Early-phase monitoring highlighted its and bolometric properties, confirming it as a normally bright event without significant peculiarities, though its light curve deviated slightly from some models like W7. SN 1994D held particular importance in cosmology due to its role in observations as part of the Key Project on the extragalactic distance scale and the High-Z Supernova Search Team efforts, where Type Ia supernovae like this served as standardized candles to measure the Hubble constant and trace the 's expansion history. Its distance helped calibrate local metrics within the . The event's brightness temporarily dominated the of its host galaxy , an S0-type system with a distance independently measured using the tip of the method, underscoring the utility of such supernovae in refining galaxy distance ladders.

Discovery

Detection

SN 1994D was discovered on March 7, 1994 UT, by Robert R. Treffers, Alexei V. Filippenko, Schuyler D. Van Dyk (), and Michael W. Richmond () as part of the Leuschner Observatory Supernova Search (LOSS). An independent discovery was reported by S. Perlmutter, G. Aldering, and the Supernova Cosmology Project team using the Katzman Automatic Imaging Telescope at . The detection occurred using an automated 0.76-m telescope equipped with a Lawrence Berkeley Laboratory CCD camera, which scanned nearby galaxies for transient events. At discovery, the supernova exhibited an R-band magnitude of 15.2 ± 0.5 and was located approximately 9 arcseconds west and 7 arcseconds north of the nucleus of its host galaxy, NGC 4526. The LOSS program routinely targeted galaxies in nearby structures such as the to identify supernovae early in their evolution, enabling timely follow-up observations. Pre-discovery images from the same survey showed no detection to an R-band limit of approximately 17 on March 1, 1994, indicating the event was rising rapidly toward peak brightness. modeling later estimated the explosion date as approximately March 3, 1994 (JD 2449414.6), consistent with the observed rise time of about 20 days to maximum. The discovery prompted immediate professional follow-up, including spectroscopy on March 9, 1994, with the 3-m Shane reflector at , which confirmed the supernova's characteristics and suggested it was about one week pre-maximum. Additional confirmations came from other observatories, including independent reports by amateur astronomers and further professional monitoring, as detailed in subsequent IAU Circulars.

Initial Classification

SN 1994D was discovered on March 7, 1994, by the Leuschner Observatory Supernova Search team using an automated 0.76-m telescope, with an initial R-band magnitude of 15.2 ± 0.5. An independent discovery was reported by the Supernova Cosmology Project team using the Katzman Automatic Imaging Telescope. The initial classification as a followed promptly from optical , which identified key diagnostic features distinguishing it from other types. The first spectrum was obtained on March 9, 1994 (UT), using the Shane 3-m reflector at Lick Observatory by A. Martel and R. W. Goodrich. This early-time observation (wavelength range 310–730 nm) showed a prominent P-Cygni profile in the Si II λ6355 line, with the absorption minimum at 604 nm indicating an expansion velocity of approximately 15,000 km/s for the high-velocity ejecta. The absence of hydrogen Balmer lines further supported the Type Ia designation, as these are characteristic of hydrogen-rich core-collapse supernovae. The spectrum also exhibited a very blue continuum, consistent with pre-maximum Type Ia events. These spectral traits closely resembled those of normal Type Ia supernovae, such as the photospheric Si II absorption and overall line profiles seen in events like SN 1990N. The Si II velocity of ~15,000 km/s at this aligned with typical values for standard Type Ia explosions shortly before peak brightness. The classification indicated SN 1994D was approximately one week prior to B-band maximum. The host galaxy, , has a heliocentric of z ≈ 0.0015 (corresponding to a of ~450 km/s), placing it at a distance of roughly 50 million light-years within the . This proximity facilitated detailed follow-up observations and underscored the supernova's potential brightness at maximum (predicted ≈ 11–12 mag).

Observations

Photometry and Light Curve

SN 1994D was subject to extensive multi-band photometric monitoring in the UBVRI filters, spanning from early March 1994 through late 1994. Observations were primarily conducted using the 1-m reflector telescope at , supplemented by data from the European Southern Observatory's (ESO) 3.6-m telescope and the Danish 1.54-m telescope at La Silla. These campaigns provided dense coverage starting approximately 13 days before B-band maximum light, enabling detailed characterization of the rise and decline phases. The reached its V-band peak brightness of 11.68 ± 0.03 mag on Julian Date (JD) 2449433.5, corresponding to March 21, 1994. The exhibited a symmetric decline typical of normal Type Ia supernovae, with a post-maximum decline rate of Δm_{15}(B) = 1.23 mag, confirming its classification as a standard candle without significant peculiarities in temporal evolution. The total radiated energy was approximately 1 \times 10^{49} erg, consistent with expectations for a thermonuclear explosion involving ~0.6 M_⊙ of nickel-56. Color evolution showed a B-V index of -0.08 mag at maximum light, indicative of minimal intrinsic blueness modified by interstellar effects. Host galaxy reddening was corrected using E(B-V) = 0.06 mag, derived from the supernova's position and galactic maps, ensuring accurate calibration. This correction aligns with the application of the Phillips relation for luminosity standardization, where the absolute V-band magnitude is estimated as M_V ≈ -19.35 + (Δm_{15} - 1.1) × (-0.69), highlighting SN 1994D's role in refining distance indicators.

Spectroscopy

The spectroscopic observations of SN 1994D provided extensive coverage from the to the near-infrared, with more than 50 spectra collected starting on March 8, 1994. These included low- to high-resolution data obtained using instruments such as the Kast spectrograph on the Shane 3-m at and the EFOSC spectrograph on the ESO New Technology Telescope (NTT). The observations spanned from pre-maximum phases through the nebular stage, enabling detailed tracking of line evolution and velocity shifts. Pre-maximum spectra revealed prominent absorption features from intermediate-mass elements, including strong Si II, S II, and Ca II lines, characteristic of expanding in a . The photospheric , traced by these lines, was approximately 12,000 km/s shortly after explosion and decreased to about 11,000 km/s by maximum light around March 21, 1994. At maximum light, the spectrum was dominated by the Si II λ6355 absorption at a of 11,000 km/s, with emerging P-Cygni profiles from iron-group elements such as Fe II and Co II beginning to indicate the onset of deeper atmospheric layers. In the nebular phase, beyond day 200 post-maximum, spectra displayed a transition to emission-dominated features, with strong forbidden lines of [Fe II] and [Ni II] dominating the optical and near-infrared regions. These lines, arising from low-density, collisionally excited gas, signified complete silicon burning throughout much of the and provided insights into the distribution of iron-peak nuclei. Velocity structure analysis across the spectral series showed gradients from outer layers at ~15,000 km/s down to minimum velocities of ~2,000 km/s in the inner , consistent with stratified composition in a thermonuclear . No signatures of were detected in any spectra, but a near-infrared feature at ~1.05 μm near maximum light has been attributed to neutral (He I) by some analyses, providing potential insights into the system, although alternative non-helium interpretations exist. High-resolution spectra also probed for circumstellar interaction, yielding upper limits on narrow Hα emission flux consistent with a low-density progenitor wind but no definitive detection of interacting material. These limits, derived from observations as early as 6.5 days post-discovery, constrained possible mass-loss rates from the pre-explosion system to below 10^{-6} M_⊙ yr^{-1}.

Imaging

High-resolution imaging of SN 1994D was obtained by the (HST) using the Wide Field and Planetary Camera 2 (WFPC2) on May 8, 1994, approximately 50 days after its peak brightness. The observations, conducted in the F555W (V-band) and F814W (I-band) filters with total exposure times of 520 seconds per filter, captured the supernova as a prominent bright spot at an of roughly 13.5, standing out against the inclined dusty disk of its host galaxy in the southwest outskirts. The WFPC2 images provided a spatial resolution of approximately 0.1 arcseconds per pixel, allowing clear isolation of the supernova position without evidence of an immediate circumstellar nebula, though prominent dust lanes in the nearby galactic disk are discernible, consistent with the supernova's projection onto an interstellar dust feature. Ground-based imaging from , including pre-explosion archival plates, enabled to pinpoint the explosion site and search for a progenitor; no such source was detected, aligning with expectations for a Type Ia event involving a faint companion system. This HST imaging demonstrated the supernova's exceptional luminosity, which at peak visual magnitude of about 11.9 briefly exceeded that of the galaxy's core, highlighting its role as a standard candle in extragalactic studies. The resulting composite image has served as an iconic example in astronomical outreach, vividly illustrating the dramatic impact of a stellar within a structured galactic environment.

Host Galaxy and Location

NGC 4526

is a classified as morphological type SAB(s)0°, featuring a weak bar and spiral-like structure without a ring, situated as a member of the approximately 15.7 ± 0.2 (stat) ± 0.4 (sys) Mpc away. This distance corresponds to a modulus of 30.98 ± 0.03 (stat) ± 0.06 (sys) mag, placing it among the nearer members of the cluster. The galaxy exhibits an apparent B-band magnitude of around 10.0, making it visible with moderate telescopes. Physically, NGC 4526 spans a of approximately 110,000 light-years across its major axis, with an estimated total mass on the order of 10^{11} solar masses. Observed nearly edge-on, it displays a prominent dust lane bisecting its disk, indicative of interstellar material in an otherwise evolved system. The galaxy's disk rotates rapidly, reaching velocities exceeding 250 km/s, which highlights its ordered despite the lenticular morphology. It hosts a central of (4.5 ± 0.4) × 10^8 M_⊙, measured from molecular gas dynamics. Star formation in NGC 4526 remains active within its disk, supported by a reservoir of molecular gas organized into giant molecular clouds that suggest recent bursts of activity. These clouds exhibit properties such as higher luminosity and density compared to those in spiral galaxies, with the galaxy's overall metallicity approaching solar values (log(Z/Z_\odot) \approx 0.2 in central regions), comparable to the and conducive to processes. As a member in the southern extension (sometimes associated with subgroup dynamics near A1367 influences), has a heliocentric systemic radial velocity of 625 ± 5 km/s. Historically, the galaxy was first cataloged by on April 13, 1784, as part of his sweeps of the Virgo region. Its dense contributes to a relatively high rate within the cluster environment, with at least two recorded events underscoring its evolutionary state. SN 1994D appeared offset from the nucleus in the central disk.

Position within the Galaxy

SN 1994D is located at equatorial coordinates RA 12h 34m 02.37s, Dec +07° 42' 04".7 (J2000 ). It lies 9.0 arcsec west and 7.8 arcsec north of the nucleus of its host galaxy , corresponding to a projected physical distance of approximately 0.8 kpc from the center at the distance of 15.7 Mpc to the galaxy. This places the supernova in the central disk of the , near but offset from the core. The explosion site is situated in a region of the galaxy's disk, distant from dense star-forming areas, with low interstellar extinction estimated at A_V ≈ 0.08 mag along the line of sight. imaging in the F555W filter reveals an environment dominated by diffuse starlight, with no nearby companion stars or H II regions detected in the immediate vicinity of the position. Pre-explosion ground-based imaging in the R band yields no detection of a progenitor source brighter than R = 21.5 mag at 3σ confidence. The to SN 1994D intersects a prominent dust lane in , resulting in minor reddening of the supernova's colors, but high-resolution spectra and imaging show no signatures of a dense circumstellar medium surrounding the site. This central offset and quiescent environment are consistent with an older , favoring a single-degenerate model for the Type Ia event and aligning with typical delay times of several gigayears.

Physical Properties

Explosion Parameters

The explosion of SN 1994D, a typical , involved the release of in the on the order of 1.4 × 10^{51} erg, consistent with models of near-Chandrasekhar-mass disruptions. The total radiated in the optical band was approximately 10^{43} erg, representing a small fraction of the initial converted to observable . These parameters were derived from simulations matched to the observed light curves and spectra, highlighting the efficiency of transport in the expanding envelope. The mass was estimated at about 1.4 M_⊙, with maximum expansion velocities of 10,000–15,000 km/s inferred from the widths and profiles of absorption lines in early spectra. This mass and velocity profile align with one-dimensional models assuming a central ignition and deflagration-to-detonation transition, producing a homologous expansion phase shortly after the blast. The decline post-maximum was primarily powered by the chain ^{56}Ni → ^{56}Co → ^{56}Fe, where the initial ^{56}Ni mass was approximately 0.6 M_⊙; the half-lives of 6.1 days for ^{56}Ni and 77 days for ^{56}Co provided the dominant energy input during the photospheric and nebular phases, respectively. At peak light, the blackbody temperature of the reached approximately 6,000 , cooling to around 4,000 about 30 days post-maximum as the expanded and recombination progressed. Electron dominated the opacity, with a photospheric τ ≈ 2 at maximum, facilitating the escape of photons while maintaining a nearly blackbody initially. Observations of yielded values below 0.3% across broadband filters near maximum light, indicating no detectable asymmetry in the geometry and supporting models of a largely spherical .

Progenitor Constraints

The system of SN 1994D is constrained by observations indicating low levels of circumstellar material. High-resolution conducted 6.5 days after revealed no narrow Hα emission at the velocity of the local (+830 km s^{-1}), with a 3σ upper limit of 2.0 × 10^{-16} erg s^{-1} cm^{-2}. modeling of this non-detection, assuming spherical and a wind speed of 10 km s^{-1}, yields an upper limit on the mass-loss rate of \dot{M} < 1.5 \times 10^{-5} M_\odot \mathrm{yr}^{-1}. This constraint disfavors single-degenerate (SD) models involving symbiotic companions with high mass-loss rates but is compatible with SD scenarios featuring a accreting from a companion at lower rates, as well as all double-degenerate (DD) merger models, which predict no circumstellar interaction. Spectral analysis further limits SD variants with a helium-star donor. The early- and late-time spectra of SN 1994D exhibit standard Type Ia features, including prominent Si II, Ca II, and lines, with no evidence of helium absorption or emission lines that would indicate material stripped from a non-degenerate helium companion. High-velocity ejecta components (up to 40,000 km s^{-1} for Ca II) suggest the presence of primordial heavy elements from the progenitor , consistent with a carbon-oxygen composition prior to explosion and low in the outer layers. The site's location in the outer disk of the lenticular host galaxy , amid an intermediate-age , implies a progenitor delay time of approximately 1–3 Gyr. This timescale aligns with both SD and DD channels involving progenitors formed from stars of ~2–4 M_\odot, though it favors systems with moderate evolutionary delays over very short or very long ones.

Scientific Significance

Contributions to Type Ia Understanding

SN 1994D was among the first Type Ia supernovae observed with high-quality spectra obtained within days of , starting approximately 12 days before maximum light, which revealed rapid changes in states, such as the sudden transition from singly to doubly ionized species around maximum light. These early-time observations provided critical data for constraining mechanisms, particularly favoring delayed detonation models where a subsonic transitions to a supersonic , as demonstrated by synthetic spectra matching the observed photospheric velocities of about 15,000 km/s and high-velocity features up to 25,000 km/s. The well-sampled of SN 1994D, covering UBVRI bands from discovery to late phases, exemplified a normal Type Ia event with a decline rate Δm_{15}(B) = 1.33 ± 0.04 mag, aiding the refinement of the Phillips relation that correlates peak with light curve shape and reduces intrinsic scatter in luminosity-distance estimates to about 0.15 mag. This standardization highlighted the uniformity of the normal branch of Type Ia supernovae, with SN 1994D exhibiting minimal spectroscopic peculiarities and serving as a benchmark template for spectral synthesis models, such as non-LTE using the W7 model that reproduce its optical and near-infrared features effectively. Nebular-phase spectra of SN 1994D, taken around 300 days post-explosion, featured broad emission lines from iron-group elements like [Fe II], [Fe III], [Co III], and [Ni II], constraining the yields of these species and supporting Chandrasekhar-mass (~1.4 M_⊙ ) explosions by favoring models that predict the observed line strengths and ratios without excessive stable production. Observations of SN 1994D informed hydrodynamical simulations by providing empirical benchmarks for rise times to bolometric maximum of approximately 18 days and early UV flux deficits, improving predictions for the initial expansion and in Type Ia , as seen in delayed models that align with the event's bolometric evolution.

Role in Distance Measurements

SN 1994D played a key role in the Key Project on the extragalactic distance scale by serving as a calibrator for distances to the , where Cepheid variables provided the primary anchor for the . The supernova's was analyzed to determine its peak apparent V-band magnitude, and using the light curve shape parameter Δm_{15} = 1.33 ± 0.04, the was calibrated to M_V = -19.15 mag via the established relation between decline rate and for Type Ia supernovae. This yielded a distance modulus to the host galaxy of (m - M)_V = 31.07 ± 0.10 mag, consistent with the galaxy's position in the foreground of the and linking local Cepheid measurements to cluster-scale distances. This distance measurement contributed to the Key Project's overall determination of the Hubble constant by integrating SN 1994D into the sample of low-redshift Type Ia supernovae calibrated against Cepheid distances in their host galaxies, enabling the extension of the distance ladder to velocities of 2000–10,000 km s^{-1}. The project ultimately derived H_0 = 71 ± 7 km/s/Mpc, with SN 1994D helping to bridge local calibrators to more distant supernovae. As a nearby (z ≈ 0.004), SN 1994D also served as a low-redshift anchor for comparisons with high-redshift supernovae observed by teams investigating cosmic expansion, aiding in the identification of early evidence for accelerated expansion driven by , though it was not a primary object in the seminal Riess-Perlmutter analyses. Error analysis for the distance to incorporated corrections for interstellar reddening along the and potential effects on the supernova's , resulting in a total uncertainty of approximately 5% after accounting for fitting and calibration systematics.

References

  1. https://arxiv.org/pdf/astro-ph/9602005
  2. https://arxiv.org/abs/1806.02900
  3. https://arxiv.org/pdf/astro-ph/9907345
  4. https://science.nasa.gov/asset/hubble/supernova-1994d-in-galaxy-ngc-4526/
  5. http://www.cbat.eps.harvard.edu/iauc/05900/05946.html
  6. https://iopscience.iop.org/article/10.1086/307947/fulltext/
  7. https://www.aanda.org/articles/aa/pdf/2007/44/aa7487-07.pdf
  8. https://ned.ipac.caltech.edu/object/NGC%204526
  9. https://ui.adsabs.harvard.edu/abs/1995AJ....109.2121R
  10. https://academic.oup.com/mnras/article/278/1/111/1033104
  11. https://iopscience.iop.org/article/10.1086/310323
  12. https://iopscience.iop.org/article/10.1086/322239/fulltext
  13. https://adsabs.harvard.edu/full/1995ApJ...443...89H
  14. https://iopscience.iop.org/article/10.1086/310752/fulltext
  15. https://arxiv.org/abs/astro-ph/9602005
  16. https://academic.oup.com/mnras/article/281/1/263/1066415
  17. https://ui.adsabs.harvard.edu/abs/1996MNRAS.283.1355C
  18. https://cdsarc.u-strasbg.fr/vizier/ftp/vizier/aa/papers/9349003/2300877.pdf
  19. https://esahubble.org/images/opo9919i/
  20. https://academic.oup.com/mnras/article-pdf/278/1/111/3459627/278-1-111.pdf
  21. https://www.eso.org/public/images/ann11014a/
  22. https://www.rochesterastronomy.org/snimages/sn1994d.html
  23. https://apod.nasa.gov/apod/ap150531.html
  24. https://iopscience.iop.org/article/10.3847/1538-4357/aac9cc
  25. https://www.universeguide.com/galaxy/ngc4526
  26. https://esahubble.org/images/potw1442a/
  27. https://ui.adsabs.harvard.edu/abs/2013Natur.494..328D/abstract
  28. https://iopscience.iop.org/article/10.1088/0004-637X/803/1/16
  29. https://www.deepskycorner.ch/obj/ngc4526.en.php
  30. http://ui.adsabs.harvard.edu/abs/1994IAUC.5951....1C/abstract
  31. https://arxiv.org/pdf/astro-ph/9610020
  32. https://ui.adsabs.harvard.edu/abs/1994AAS...185.1206H/abstract
  33. https://arxiv.org/pdf/astro-ph/9907252
  34. https://arxiv.org/pdf/astro-ph/9602025.pdf
  35. https://arxiv.org/pdf/astro-ph/9602005.pdf
  36. https://arxiv.org/pdf/astro-ph/9602155.pdf
  37. https://arxiv.org/abs/astro-ph/9610020
  38. https://arxiv.org/pdf/astro-ph/0603407
  39. https://iopscience.iop.org/article/10.1086/310752
  40. https://arxiv.org/pdf/astro-ph/0012376.pdf
  41. https://arxiv.org/pdf/astro-ph/0603407.pdf
Add your contribution
Related Hubs
User Avatar
No comments yet.